Giancarlo Carli is expert on physiological correlates of behavior approached by different experimental models.
Tonic immobility (TI) is usually associated to reduction in limb muscle tone and depression of mono- and polysynatic reflexes. Somatic reflexes do not change during TI associated with increase in muscle tone (110, 112). TI associated to depression of somatic reflexes may be elicited following acute decortication, pre-collicular decerebration and decerebellation (109, 111). Short lasting episodes of rhythmic slow activity in the hippocampus occurs during voluntary movements, arousal, attention, learning and , at low frequency, during TI. In particular, this rhythm occurs during TI induction, is absent at TI onset, and gradually increases in number of episodes, total amount, duration of a single episode and mean frequency. Since TI duration is negatively related to the frequency of occurrence of rhythmic slow activity episodes in the hippocampus, it is suggested that the higher is the reduction in the parameters of rhythmic slow activity episodes, the lower is the awarenness and the deeper is the TI state (93). Morever the greater is the percentage of high voltage slow vawes in the EEG, the lower is the frequency of occurrence of rhythmic activity in the hippocampus. The latter activity in the hippocampus is suppressed following the presentation of a staffed sparrow awak and is associated with high voltage slow vawes in the EEG. It has to be underlined that similar rhythms occour during TI (85).
During TI induction blood pressure and heart rate show some oscillations above and below control levels resulting slightly increased at TI onset. During TI they remain at basal levels, being decreased on long lasting TI episodes associated with high voltage slow vawes in the EEG. Similar cardiovascular results are recorded in decorticated rabbits (103). If TI is induced in a rabbit non adapted to the environment and exploring the recording chamber, heart rate is sharply reduced during TI. After 12 hr adaptation, the animal displays quiet wakefulness, heart rate levels are much lower, being adjusted at the levels reached during TI induced during adaptation. If TI is induced in cage adapted rabbits, heart rate remains at basal levels (103). Heart rate and blood pressure do not change during restraint-sustained immobility obtained by clips application (86). During TI animals can extinguish a previous learned avoidance response and recall it after TI termination (105).
At TI onset, within 1-2 min , usually there is a gradual development of high voltage slow vawes in the EEG that may be interrupted by novel/dynamic external stimuli that not necessarily terminate the TI episode. Rabbits gradually adapt to the recording cage and develop high voltage slow vawes in EEG. If TI is induced after 2 hrs of cage residency, TI displays a duration similar to control but associated to low voltage fast activity. If TI is induced in a background of persistent nociceptive stimulation, not only the nociceptive behavior and the EEG low voltage fast activity are fully suppressed, but there is development of high voltage slow vawes in the EEG (102). Similar results are obtained after denervation of dorsal and dorsolateral skin extending from the neck to the tail of the rabbit. In conclusion, EEG pattern during TI depends upon the events preceding TI and exclude a role of pressure stimuli occurring in reverse supine position ( 102, 104). Since at sleep onset in humans there is development of high voltage high vawes, loss of consciuosness and sensory deafferentation related to the activity of thalamic reticular nucleous, the so-called thalamic gate, it is suggested that anesthesia could occur during TI (102). Interestingly, during TI there is a generalized reduction in brain cerebral glucose utilization (97), an overall depression known to occurr during anesthesia and following β-endorphin injection. A β-endorphin mechanism might be involved in TI since TI duration is increased by morphine and this effect is abolished by naloxone (95). Moreover, in TI habituated rabbits, formalin pain restores TI and this effect is abolished by naloxone. Interstingly, intracerebral injection of a specific β-EP antibody increases TI duration but decreases TI duration following formalin pain. In conclusion, in absence of pain, β-EP stimulates arousal mechnisms involved in restoring normal posture and vigilance whereas, in presence of pain, potetentiates it (58). In conclusion these data support the hypthesis that β-endorphin mechanism could selectively affect the nociceptive transmission eliciting analgesia by the thalamic gate The opioid analgesia is resistent to barbiturates, the thalamic gate may be interrupted by dynamic innocuous/nociceceptive stimuli (95).
Melatonin is a neurohormone involved in synchronizing several biological functions including analgesia. In rats, during clips induced immobility, microinjection of melatonin into both vlPAG and into dPAG increases the tail flick latency, the analgesic effect being greater for the vlPAG than in dPAG (6). In a separate experiment, the same PAG injections do not affect the immobility duration. The analgesic effect of melatonin is mediated by melatonin T2 receptors ( MT2) that are greatly represented at vlPAG and poorly represented at dPAG, where melatonin acts as GABAA agonist. If analgesia and immobility testing are combined, dPAG microinjection blocks the TI analgesia and reduces immobility duration. In conclusion, melatonin confirms the opposite role of dPAG and vlPAG on clip induced analgesia according to its effects on opioids or on GABAergic mechanisms (6).
The corticosteroid reactivity has been regarded as a trait of animal personality. In male rabbits there is a positive correlation between corticosterone basal levels and TI duration, with higher levels in susceptible with respect to in unsusceptible animals. This finding suggests that a more active adrenocortical system may predispose animals to a higher TI response (98). If TI induction is not followed by TI, there is an immediate increase in corticosterone that is still present at the 15 min sample. If induction is followed by TI, corticosterone plasma levels are not affected in the two samples after TI, a clear indication that during TI there is a recovery from the stressful condition of induction (77). Repeated daily TI inductions lead to gradual decrease in TI duration and increase in corticosterone plasma levels that reach a peack at habituation day. On this day the increased levels of corticosterone depend only on the induction, and the induction stimulus becomes gradually inefficient in eliciting TI but more efficient in increasing corticosterone (94). The stress-related corticosterone increase is often accompanied by a decrease in testosterone. Testosterone plasma levels, indeed, decrease following induction and recovers during TI to the pre-induction values, a confirmation of our hypothesis that TI represents an adaptive recovery mechanism, i.e. a homeostatic process of a previous the stress-response (100). Serotonin (5-HT) is a neutransmitter involved in recovery mechanisms occurring during TI (88). Repeated spaced trials of TI induction and induction followed by TI result in decrease in 5-HT and its metabolite 5HIAA in the striatum , i.e an accelerated demolition process during induction alone, whereas following induction plus TI a decrease in 5-HT but not in 5HIAA, an indication of an active recovery process. Moreover in the striatum, at individual level, a negative correlation is found between 5HT levels and total mean time TI durations: the longer is TI duration, following sensitization, the greater is the decrease in 5-HT (88).
Experimental pain models in animals
The experimental model of persistent pain by formalin in rabbits and later in rats has provided a contribution to understand the mechanisms of persisten pain. It has been suggested that the first phase of formalin pain is due toTRPA-1 mediated excitation of nociceptors, the second phase to inflammatory processes elicited nociceptors sensitization and /or central sensitization. Behavioral testing, dorsal root neuron culture, patch clamp recording , intracellular ratiometric calcium measurements, measurements of plasma extravasation and spectroscopic formaldehide measurements associated to mathematical modeling suggest a peripherally generated biphasic response. After an initial depolarization, the interphase is a result of hyperpolarization and transient inactivation by formaldehide of the “surviving neurons; their recovery and the centrifugal spread of formalin induce a second phase of nocicdeptive activity before the concentration falls below threshold (11). Acute noxious situations may induce activation of central opioid mechanisms, that in turn exert analgesic effects. The study of beta-endorphin-like immune reactivity -like reactivity in rats revealed that , following a small dose of formalin injection there is a gradual increase of beta-endorphin-like immune reactivity in PAG and in posteromedial and ventomedial thalamus that persists for about 2 hrs. Microinjction of an anti- beta-endorphin serum into rat lateral ventricle increased the formalin pain manifestations only during the second phase , i.e. revealing the analgesic effect of the beta-endorphin released by the tonic pain (75). Ipsilateral forelinb injection of formalin elicits nociceptive responses, mainly licking, not only ipsilaterally but also contralaterally, although this mirror response displays less intensity and duration. The 2-deoxiglucose technique reveals bilateral metabolic changes both in spinal dorsal and ventral horns, in gray matter surrounding the central canal and in anterolateral and ventrolateral funiculi (71). In rats formalin elicits a biphasic limb licking and licking around the injected site only if is injected into the dorsal hind paw, having no effect on the subcutaneous tissue into the tight and into the quadriceps. Phasic flexing is higher following dorsal hind paw injection and lower into the other two sites, jerking the injected limb occours only during the second phase in all sites being more frequent following hind paw injection (61). The effect of 2 different doses of formalin injection on nociceptive and standard activity behavion has been studied in rats receiving larger doses that display greater pain intensity, reduction in rearing , olfactory behavior and locomotor activity. The lower dose shows a general behavioral activation and objects approach associated with absence in sleep-like behavior (57). In rabbits a small dose of formalin elicits a short pain associated to increase in rearing and locomotor activity that lasts more than 24 hrs: these effects are abolished by microinjction of an anti-BEP serum into the lateral ventricle ( 69, 74). A much greater formalin dose elicits licking lasting more that 24 hrs whereas locomotor activity is decreased only during the 10 min after injection (69). Many animal species hoard food by carrying it to their home area. In rats treated with formalin the availability of food resulted shorter duration in licking , self groming and inactivity with no effect on exploratory activity and hoarding parameters. However, flexing and paw jerk were increased, an indication that the decrease in licking is related to motvation rather than analgesia (52). A larger dose of formalin elicits higher plasma levels of ACTH, β-EP and IL-6 than controls and a strong nociceptive responses with no modification in general locomotor activity. A lower dose elicits a a decrease in ACTH, β-EP plasma levels and an increase in motor activity with respect to control, whereas corticosterone does not change. The persistent decrease in the release of pituitary hormones suggest a different functional adaptation to different levels of tonic pain (60).
Following a large dose of formalin injection, licking and flexing last more in female than in male rats during both phases, whereas paw jeck frequency is similar in both sexes. It has to be underlined that licking and flexing are controlled by more complex supraspinal mechanisms whereas paw jerking is controlled by spinal mechanisms (66). In a study of the effects of a novel environment, i.e. standard hole board, on formalin pain it was shown that females display more licking, and more locomotion and less faecal boluses than males . In control conditions , females show higher percentage in inner line crossing and in rearing values than males: formalin decreased the latter two parameters in females and increased the inner lines crossing in males. Since the latency in licking and paw-keck are similar in the two sexes, it is suggested that formalin pain increases the motivation to explore the environment in males and has an opposite effect in females (59). Hippocampal coline acetyltransferase, ACTH and corticosterne levels are similar in control male and female rats. Both the small and the large formalin dose decrease the hippocampal coline acetyltransferase in males but not in females and increase ACTH in females, whereas corticosterone is not affected in both sexes. In animals treated with the higher formalin dose there is a positive correlations between hippocampal coline acetyltransferase and licking duration in males and a negative correlation in females. It is suggested that the decrease in hippocampal coline acetyltransferase in males represents a compensatoty adaptation that reduces the unpleasant information related to pain, whereas for females is more adaptive to maintain a high level of arousal (53). Moreover, in male rats, hippocampal coline acetyltransferase increases following exposition to novelty, decreases following formalin test only in animals considered inactive during the novelty test, while no modifications occur in the active ones. Restraint increases corticosterone but does not affect hippocampal coline acetyltransferase. It is suggested that the hippocampal response depends by the type of behavioral state of the animal at the time of formalin injection (51). The involvmentof the cholinergic system in pain moduation has been evaluated by the formalin test that elicits both tonic and phasic nociceptive responses. The muscarinic cholinergic agonist oxotremorin induces a dose- and time-dependent reduction in all the evoked nociceptive responses. Oxotremorin decreases rearing and line crossing and, in part, exploratory activity, whereas self-grooming is increased. The latter two effects are abolished by formalin treatment. β-endorphin is increased in the septum and in the hypothalamus in formalin treated rats independently from oxitremorine treatment. It is suggested that cholinergic mechanisms modulate both spinal and supraspinal nociceptive responses (47). The environment may affect recovery from inflammatory pain. Rats housed in physically enriched, socially , socially plus enriched environment and in isolation received an intraarticular carrageenan injection into their knee and the allodynia was assessed by the von Frey test for four weeks. Results show that the allodynia lasts 28 days in socially isolated rats and only 21 days in rats housed in the physical plus social enriched environment. In socially enriched rats allodynia lasted 24 days. The Elevated Plus_Maze test shows a similar anxiety levels among groups. Results suggest that physical and social aspects of the environment improve recovery from inflammatory pain and the two aspects are inter-dependent (27).
Hypnotizability and pain control
In highgly susceptible subjects (Highs)suggestion of analgesia increases the pain threshold of the nociceptive flexor reflex and decreases the amplitude of late of somatosensory cerebral evocked potential. In a subgroup of patients the threshold of the nociceptive reflex is decreased and the amplitude increased. The tactile reflex is reduced during relaxation and remains at that level during suggested analgesia, although their nociceptive reflex is increased. In both subgroups pain threshold is similar in control condition and following relaxation . The authors suggest that the increase in the nociceptive reflex during suggested analgesia might be due to the fact that some subjects are able to use a strategy to anticipate pain (48). When blood flow increases, as occurs soon after an occlusion of the vessel, endotelial cells elicits vasodilation mainly through the production of nitric oxide. This endotelial function is transiently reduced by mental stress and this endotelial dysfunction is much lower in Highs in the waking and in the hypnotic state with respect to low susceptible subjects (Lows). Painful stimulation elicits an endotelial dysfunction that is lower in Highs than in Lows. After suggestion of analgesia only Highs report analgesia during painful stimulation and the endotelial function is restored. Highs and Lows sensitivity in flow endotelial function to nociceptive stimulation suggests a natural protection of Highs against stress-related risk (42). Hypnotizability is associated with differences in flow-mediated delation that is largely due to NO and NO synthase. Endotelial syntase is encoded by NOS3 locus. The aim of the study was to investigate the associationn between genetic polymorphysms of NOS3 involved in NO blood levels and hypnotizability.The study reports the first evidence of a genetic substrate of hypnotizability-related to vascular responses. According to the “NO hypothesis” the high availability of NO in Highs could be responsible for their high immaginability and their equivalence between imagery and perception (29). In fibromyalgia patients the role of suggestibility, hypnotizability, relaxation , expectancy , perceived control of pain in hypnotic analgesia has been investigated. During hypnotic suggestions of analgesia fibromyalgic patients report analgesia, but Lows report an analgesia that is similar during mental stress and hypnotic relaxation. In healthy controls, Lows do not report any change in pain perception during nociceptive stimulation associated with relaxation and suggestion of analgesia. Thus, chronic pain seams to be responsible for the paradoxical response of non hypnotizable patients to hypnotic suggestions (36). Heart rate and heart rate variability have been recorded during 2 min nociceptive stimuli elicited by a pressure algometer applied at the second costochondral junction. During nocicetive-pressure stimulation with and without suggestions of analgesia there is no difference between Highs and Lows in heart rate and heart rate variability parameters. This absence of modulation could be related to the fact that this experiment includes only females since females, differently from males, do not exibit any correlation between pain intensity and heart rate (35, 43). The possible role of cannabinoids on hypnotizability-related pain control has been investigated by using the fatty acid amide hydrolase degration in Highs. The allele of fatty acid amide hydrolase C385A polymorphysm ( rs324420 is associated with lower allele activity. No significant difference was observed among groups. However the A allele frequency showed a significant trend to increase from Lows to controls and from controil to Highs. These small differences in the fatty acid amide hydrolase could be amplified by the interactions of carbaminoids with other neurotransmitters (2). There is evidence that, in subjects with high ipnotizability , imagined somatosensory stimulation could involuntaary activate the neural circuits involved in the modulation of reflex action. The displacement of the centre of pressure was studied during imagery of leg pain and during imagery of tactile stimulation of the same leg and of throat pain. Results show that the vividness imagery of leg pain was higher in Highs than in Lows for all tasks and only Highs reported pain during imagery of pain and tactile stimuli. The imagined leg pain was associated with dispacement of the centre of pressure towards the leg opposite of the imagined leg pain and increased the center pressure velocity and area of escursion. In conclusion high ipnotizability is responsible for the postural effects of pain imagery (20). The diffuse inhibitory control is a well known mechanism activated by noxious stimuly such as the cold pressor test that could also be involved in hypnotic analgesia. In Highs, medium susceptible and Lows both suggestions of analgesia and cold pressor test reduce pain intensity , the reduction being grater in Highs than in medium and Lows. Results are particularly interesting since medium and Highs represents the 85% of the population that is able to accept analgesia and that noxious inhibitory control may exert its action through both sensory and cognitive mechanisms (5). Self reports of pain intensity and neutral tactile perception were collected during imagery of nociceptive and neutral tactile stimulation. Highs exibited greater abilities, greater absorption, Behavioral Inhibition System Activity and psychological well-being with respect to Lows. Highs also reported lower scores in pain perception than in tactile perception , whereas Lows two perceptions scores did not differ. This suggests that the efficacy of pain imagery in Highs may be relatd to higher sensitivity to negative or painful outcomes and, consequently, deeper attitude to avoid/inhibit situations possibly inducing them (14) . In a study of cold pressor test it has been shown that suggestions for analgesia increase the duration of the test and decrease heart rate in both Highs and Lows, but decreasing pain intensity and increasung pain thresholds only in Highs. Suggestion of analgesia did not affect systolic blood pressure, skin conduction and skin blood flow, an indication that the parasympathetic activity is responsible for heart rate reduction induced by suggestions in both groups.Thus suggestions of analgesia in heathy subjects may modulate autonomic pain responses also in Lows (17). The Behavioral Activation/Inhibition System (BIS/BAS) accounts for the cortical dynamics associated with pain modulation and for the Highs low efficacy of pain imagery. BIS is sensitive to signals of punishment/non reward and involved in negative feelings, BAS, associated with high levels of dopamine, is sensitive to potential rewards and motivations to sick out positive experiences. Heart rate response to pain is and index of visceral activation that however is similar in Highs and Lows during suggested analgesia. In a study of the correlations between BIS/BAS scores, heart rate cold pressor test and hypnotic susceptibilty it has been shown that Highs have similar BIS/BAS scores , more analgesia to the cold pressor test, lower basal heart rate before the test and a positive correlation between heart rate before the test and pain threshold during suggestions of analgesia, an indication supporting the body-mind hypothesis of subjective experience of pain. The activity of the BIS/BAS system partially accounts for the hypnotizability related differences in the possible relevaance of interoceptive activity in pain experience (3). In order to assees the role of cerebellum on pain perception , the trascranial anodal and cathodal electrical stimulation were associated to laser evocked nociceptive stimulation. Cathodal polarization dampened perceptive thresold and increased the pain VAS scores, while anodal polarization had an opposite effect. It has to be underlined that patients with cerebellar infarction report hyperalgia (7). In Highs smaller evocked potentials with longer latencies are recorded both following anodal and cathodal laser stimulation with respect to controls. Both stimulations do not not affect pain perception but anodal stimulation increases the amplitude of the evoked potentials wheares cathodal stimulation is uneffective. In controls, anodal stimulation decreases pain perception decreasing the amplidude and increasing the amplitude of evocked potentials; cathodal stimulation results opposite effects. In conclusion, Highs shows impaired cerebellar pain modulation and altered cerebral cortical representation of pain (4).
Physiological correlates of hypnotizability
Physiological correlates of hypnotizability have been investigated in Highs and ìn Lows healthy subjects performing a variety of tasks. Initially it was shown that human monosynaptic reflex decreases during recording sessions in hypnotized Highs receiving suggestions of simple relaxation, anesthesia, analgesia and paralysis. However in Highs the same reflex depression occurs during long-lasting control conditions, whereas in Lows the reflex amplitude does not change. In conclusion the reflex depression is related to hypnotic susceptibility rather than hypnosis (79). In order to study motoneurons excitability, F wave frequency was elicited during hypnosis without instructions in Highs, and during simple relaxation in Highs and Lows. Results show that F wave frequency decreases only in flexor motoneurons in the righ upper limb in hypnotized Highs, an effect that persists after hypnosis termination. This reduction occurs during the last period of relaxation in highly susceptible non-hypnotized subjects. Lows do not change the F wave frequency. Results suggest that hypnosis induction represents an useful method to reveal trait differences (46). Highs and Lows differ in capacity of attention and attention represents one component of equilibrium. The influences of hypnotizability on postural control were assessed through a non ionising optoelectronic system that provided detailed information about body position and movements. Results shows that Lows are more sensitive to eye closure and react with a greater backward sway than Highs. Thus, the control of stance is more effective in Highs and the internal space reference is related to hypnotizability (45).With the same equipment awake Highs and Lows received an explicit suggestion of backward falling with and without hypnosis induction. In Highs with and without hypnosis the suggestion elicited the backward body expected in the corresponding real situation, whereas Lows did show any response. Results suggests that in Highs there is a possible equivalence of imagery and perception (42 ). Postural control has been investigated in subjects standing uprigh with eye closed during visual and tactile imagery tasks and during mental computation. Highs judged tactile imagery less efforfull and more vivid than Lows and , differently from Lows , their body sway was not affected by the cognitive tasks (40). In a further paper (39) it was shown that Highs body sway was also not modified by simultaneous imagery of globally reduced perception , whereas Lows increased their sway while perceiving the decreased sensory availability. Thus Highs and Lows differ in the mechanisms of imagery perception and sensorymotor integration (39). Alteration of propioceptive system by standing barefoot on an stabilometric plateform with eye closure allows to monitor the movement of the centre of pressure. The stabilogram diffusion analysis shows that Highs and Lows exibit different postural control and that Highs have a wide range of stable positions and different internal reference systems than Lows (34). In a further study it has been studied the effect of mental computation in a stable and unstable postural support. In the unstable postural support condition mental computation increases the variability in the center of pressure in Highs and decreases the ratio between center of pressure trajectory length in Lows. Thus, the attentional related differences between Highs and Lows in body sway are critical only when the task in more difficult as occurs when standing in the unstable support (30). However, if the task is extremely demanding such as maintaining balance while standing with open or closed eyes in a seesaw platform allowing roll movements, there is no difference between Highs and Lows in inclination area and time. Results suggest that Highs’ postural control is centrally driven in response to easy postural tasks and peripherally driven in response to difficult tasks (28). Finally, in another model slightly more demanding and very difficult postural conditions, such as feet together bipedal posture and one legged stance, respectively, the body sway is not modulated by hypnotizability(13). The early component of the vestibulosponal reflex is not affected by voluntary control, its amplitude depends upon stimulus intensity and the plan of body sway depends on the position of the head with respect to the trunk. This model is suitable to test the hypothesis that imagery is translated in real sensory experience and induces a real involontary behavior in not hypnotized Highs. Constructive and obstructive imagines have been used during elicitation of the vestibulospinal reflex. Results suggest that in Highs imagery is effective in eliciting involuntary behavior conguent with the corresponding perception . In addition, obstructive imageries may be effective also in good imagers Lows, an effect that might be useful for imagery-training rehabilitation ( 25). Subjects asked to walk straigh, blidfolded, during real and imagined head rotation and mental computation had to detect the amount of veering. Highs detect deviation from straight trajectory better than Lows and, in basal conditions, the walking direction is more straight and less influenced by mental computation and by real and imagined head rotation than in Lows. (23). During backward head extension, that impairs the vestibular information, there is a similar increase in the instability in Highs and Lows. Moreover also effort to walking straight ahead with eye closed and extended head forward is similar in Highs and Lows. Highs, however, can improve in walking straight across consecutive trials (22). There is evidence that visual and somatic imageries are associated with modulation of EEG alpha and theta band amplitude during upright stance. This is likely due to the fact that the standing posture is more demanding and reduces attentional resources. Sitting subject report higher vividess and lower effort for visual than for somesthesic imageries in Highs and Lows. Highs report widewspread alpha desynchonization and slightly different EEG patterns whereas Lows show segregated alpha and theta desynchonization and no difference between tasks. Thus similar subjective experiences are associated with different EEG modulation according to hypnosis susceptibility (26).
The visual recognition of haptically explored objects involves an interaction among imaginal abilities and preferences in the sensory modality of imagery. The visual recognition of ‘nonmeaningful’, unfamiliar objects bimanually explored is faster and more accurate in Highs than with Lows but improves with trial repetition in both groups. Results suggest that hypnotizability levels may be associated with specific modes of sensory integration and/or imagery(21). A further experiment shows that absence of any hypnotizability-related difference in recognition frequencies after unimanual exploration. In addition, recognition frequency of the right and left hand is comparable in Highs as in Lows, while slight differences are found in recognition time. It is suggested that hemispheric co-operation played a key role in the better performance of Highs in the bimanual task previously studied. In the unimanual exploration, the task’s characteristics, favoring the left hand, hypnotizability-related cerebral asymmetry, favoring the right hand in Highs and the possible preferential verbal style of recognition favoring the right hand in Lows, antagonize each other and prevent the occurrence of major differences between the performance of Highs and Lows (16). Blindfolded subjects are able to reproduce paths connected at acute or obtuse angles. Highs and Lows were asked to made reproduction attempts after path exploration performed by one finger, with or without concomitant cognitive activities (mental computation or imagery of exploring an angle larger than the explored one). The variables analyzed were: subjective experience (scores of the exploring effort, reproduction difficulty, perceived accuracy of reproduction, attention to mental computation and efficacy of imagery), exploration time, relative error in reproduction (under or overestimation) and the percentage of “successful” trials (absolute error <10°). Results show that the subjective experience of exploration/reproduction and the exploration times are similar in Highs and Lows and that all subjects underestimate the explored angles and reproduce the acute angle more accurately than the obtuse one. Highs exhibit a larger number of successful trials after exploration of the obtuse angle, while Lows (males) decrease their relative error in the reproduction of the acute angle. In conclusion, in the more demanding condition of reproducing an obtuse angle, the Highs’ reproduction was more accurate and more independent of cognitive load than that of Lows (19).The hypnotizability-related differences observed in sensorimotor integration suggest a major role of the cerebellum in the peculiar performance of Highs). Highs’ performance in the classical cerebellar Prism Adaptation Test is significantly less accurate and more variable than the Lows’ one, even though the two groups shared the same characteristics of adaptation to prismatic lenses. These findings could account for earlier reports of hypnotizability-related differences in postural control and blink rate, as they indicate that hypnotizability influences the cerebellar control of sensorimotor integration(8).
The effects of hypnotizability on relaxation has been investigated by recording mean values and spectral variability of heart rate, blood pressure, and skin blood flow in Higs and Lows. Both groups reported similar subjective relaxation. Highs exibit a parasympathetic prevalence and a lower renin-angiotensin activity with respect to Lows. Hypnotizability does not affect blood pressure and its variability but modulates the skin blood flow across the session only in Lows. Thus, hypnotizability modulates cardiovascular activity during simple relaxation and may have a protective role against cardiovascular disease (17). The differences in written language has been assessed in Highs and Lows by analysing their writing products. Subjects were asked to write short texts in response to highly imaginative scenarios in standard conditions. Results show that Highs’ texts were more sophisticated due to a higher number of abstract nouns, more intense and imaginative due to a larger number of similes, metaphors, and onomatopoeias, and less detailed due to a higher nouns-to-adjectives ratio with respect to Lows’ texts. The differences in the use of abstract nouns and highly imageable expressions are discussed in relation to the preeminent left-hemisphere activity of Highs during wakefulness and to a possibly different involvement of the precuneus, which is involved in hypnotic phenomena (18).
The model of sham rage behavior has been used to demostrate that behavior may be inhibited by activation of the medial reticular formation (136) and the role of descending hypothalamic information projecting to the brain stem for the manifestations of sham rage (135). Finally it has been shown that sham rage behavior can be elicited by electrical stimulation of group I muscle afferents , a demonstration that information from muscle spindles and tendon organ may have access to behavioral –regulating mechanisms (129, 114).
Electrolitic lesions show that neither ascending nor the descending components of the limbic-midbrain circuit exert any essential role on REM sleep in cats (134, 132). Brain stem lesions suggest that, in cats, the neurons regulating REM sleep are concentrated within the middle and, probably, caudal portions of nucleous reticularis pontis oralis (133).
During the bursts of eye movements of REM sleep there is a block cutaneous information that is due to a pre- (121, 124)and a post-synaptic mechanism (123, 130). These effects are abolished by bilateral distruction of the entire vestibular complex (122). The polysynaptic responses, evocked by high threshold cutaneous and muscle afferents both at the level of ipsilateral spinal ascending tracts and at cerebellar cortex, are abolished both during the arousal response and during the bursts of eye movements of REM sleep. On the contrary, the monosynaptic responses evoked by low threshold stimuli are not affected (128, 117, 116, 115). Persistent formalin pain differently affects sleep phases in cats. On formalin injection day there is a decrease in total sleep, deep sleep and REM sleep and sharp increase in wakefulness and light sleep. The sleep latency increases from light sleep, deep sleep and REM sleep and the amount of recovery depends upon sleep debt and pain intensity (81)
Mechanoceptors and propioceptors
In a project of brain stem control of muscle spindles in decrerebrate cats it has been shown that the Deiter’s nucleous may activate the extrafusal muscle fibers independently from the gamma loop (119, 126). The Deiter’ nucleuous affects muscle spindles through a mono- and a polysynaptic pathway (125). According to electrical stimulation, the eight nerve exerts a greater excitation of skeletomotor and fusimotor activity than the vestibular nuclei and the reticular formation (118). By using a differential pharmacological block of intrafusal and extrafusal junctions, it has been possible to reveal that the excitation of spindle receptors , although occurring s concomitantly with extrafusal muscle contractions, is fusimotor in origin and not related to passive factors(117, 120, 126).
Vibration sensation of the glabrous skin is a dual sense , flutter and vibration that is mediated by differents sets of receptors. Psychophysical experiments for detection of thresholds of oscillating mechanical stimuli were performed in trained humans and monkeys. Results reveal that both primates possess similar detection thresholds and reaction times. Recording from single fibers of anesthetized monkeys revealed that flutter, elicited by low frequency oscillation, is mediated by Meisner receptors, and vibration, elicited by high frequency oscillations, is mediated by Pacinian receptors (108). In heathy humans there is a relationship between detection threshold and conduction velocity of the nerve innervating the corresponding hand area stimulated by mechanichal sinusoids.This occours for the vibrations frequencies eliciting flutters and for those eliciting the vibration sensation (83).
In decerebrate unanesthetized cats electrical stimulation of the knee joint nerve elicits short latency , wide spread mossy fibers evoked potentials and more restricted long latency climbing responses. (106, 107). Moreover, single unit recording of slowly adapting receptors from posterior joint nerve sensitive to joint rotation are single spot poorly sensitive to perpendicularl pressure and vibratory stimuli. Quickly adapting receptors are particularly sensitive to low amplitude high frequency vibratory stimuli. Slowly adapting muscle afferents travelling in the same hip articular nerve also display a high sensitivity to vibratory stimuli (80). Recordings from area 3a of the cat somatosensory cortex show that there are slowly adapting neurons responding exclusively to hip joint rotation excited by periarticular muscles afferents. Results suggest that the area 3a neurons provide information about position sense relaying on muscle information (80).
Psychological control of post-surgical pain
A model of psycological control of post-thoracotomy pain has been in use in the Department of Anesthesia and Rehanimation at Bologna University, Italy. The procedure consists in avoid narcotic drug administration and limit the use of other analgesics in the early post-operative period. The method involves the use of persuasion and social support to create a psychological set in which the expectation is to exert self control of post-operative pain by generating coping strategies. After surgery pain intensity is positively related to pain duration whereas pain latency is negatively related to both intensity and duration. Morever, pain intensity is predictable from both state anxiety and psychoasthenia scales , pain latency is predictable from both state anxiety and masculinity/feminility, pain duration, aggressivity and hysteria Results suggest that personality traits constitute strong modulatory factors of the overall pain experience (76). The expected emotional coping response is related to the whole pain experience. Self-control expectancy is associated with mastery behaviors in previous pains,vicarious experiences and personality traits (72). Patients who had previously been subjected to medical pain experience report a greater pain intensity. The patients who had reported poor tolerance in the original family experience both earlier and more severe pain (70). Half of the studied patients assumed certain body positions to alleviate pain and disconfort by maintaining the same position. Most of these patients reported that the maintained antalgic position was related to the pain site, elicited a considerable sense of well being and, in half of them, a real decrease in pain intensity (64). Other patients used mental coping strategies obtaining a moderate decrease either in pain intensity or in stress (54). After surgery 30% of patients requested and obtained pain killers. Requests were more frequent in the earlier days after surgery in younger patients with lower educational level, and were not related to pain intensity. Pain killers were asked by patients reporting earlier, more severe and longer lasting post-thoracotomy pain. The patients that self defined as “passive”asked more drugs than the “active” ones. Patients who asked pain killers had higher scores in psyhopathic deviate, paranoia, psychoasthenia , schyzophrenia , neurocitism, anxiety trait and anxiety state. The stratified regression analysis revealed that intensity and duration are the most predictive factors of request for pain killers, highlighthing the critical role of pain summation (55).
Fibromyalgia is a syndrome of unknown origin which displays interesting aspects, including deep pain and hyperalgesia to deep and superficial stimuli. There is agreament that fibramyalgia pain is not supported by specific muscle or other peripheral pathology, but rather by disordered sensory processing at the central level. The criteria for classification of fibromyalgia are the presence of diffuse musculoskeletal pain and tenderness at 11 or more tender point sides. The aim of this study was to assess the psychphysical and clinical differences between fibromyalgia patients and patients with multiregional pain and a lower number of tender points that do not reach these criteria. Results show that in patients affected by chronic musculoskeletal pain , as the extent of pain and the number of tender points increases, the pain thresholds to superficial and deep stimuli decreases, while the number of psychophysical tests in which the values are lower than in the heathy subjects increases. Morever, the reactivity of the nociceptive system is modified in all groups of patients studied but to different degrees. This confirms the opinion that fibromyalgia is a clinical syndrome at the extremity of a continuum, rather than a defined disease syndrome (48). The effects of a 3-week residential multidisciplinary non-pharmacological treatment program were studied in fibromyalgic patients. Particularly, the program included individual prescribed and monitored aerobic exercize , relaxation techniques , educational sessions, cognitive behavioral therapy and the evaluation of the diurnal rhythm of salivary cortisol as expression of the hypthalamus-hypophysis axis . At the end of the program aerobic capacity improved, the diurnal rhythm of plasma cortisol was restored and was associated with an increase in corticosteroid-α mRNA expression. Moreover, the pain intensity, the number of tender points, the extension of body pain areas and pain expression scores decreased. In conclusion data suggest that the approach to symptom management should address the psychological, funtional and physical components of fibromyalgia ( 42). The long term efficacy of this treatment protocol was tested after 2, 5,and 12 months. At the end of treatment patients received individual prescriptions of exercize intensity, frequency and duration according to the level of aerobic fitness resulting from tests performed during the control sessions. Results show that the clinical symptoms and the aerobic fitness of fibromyalgic patients remained significantly improved after one year (34). The use of unidimensional scales to measre chronic pain intensity has been critized because of the multidimensional nature of pain. Result show that , in fibromyalgic patients, the scores of unidimentional pain intensity scales mainly refect sensory pain dimension assessed by a multidimensional affect and pain questionnaire. On the other hand, patients had difficulty in distinguishing between sensory and emotional information. It is suggested that to obtain a complete picture of the status and needs of any given patient several unidimensional rating scales should be used to measure somatosensory and emotional pain aspect separately (39). There is a mistaken assumption that health can be equated with absence of illness and hat well being is equal to absence of distress. In fibromyalgic patients psychlogical ditress is uniquely predicted from higher age and more physical disability and related to more intense pain and higher tender points count. On the other hand well being decreases with higher disability and is independent of age, pain intensity and tender point count. Thus, well being is a separate, partly independent dimension of mental health that should be assessed in chronic pain patients (38). Comorbid conditions independently associated with chronic pain increase the odds of reporting chronic pain in an additive manner. It has been suggested that vulvodynia could be considered as a localized expression of the chronic widespread syndrome , i. e fibromyalgia. In the present experiments the clinical diagnosis of vulvodynia was associated with the Q-tip pressure pain test and with the Kegel manoeuvre to assess the tonicity of pelvic floor muscles. Results show that fibromyalgic patients with vulvodynia show a higher number of associated symtoms than fibromyalgic patients. Half of the fibromyalgic patients with vulvodynia were positive to the Kegel manoeuvre , dispalyed higher scores in widespread pain intensity, STAI-Y2 and CESD levels than Kegel negative patients. It is suggested that coital pain develops in patients with higher fibromyalgig symtom severity due to cooperative effects of peripheral and central sensitization (10). Dietary supplementation of omega-3 is becoming popular as a complemtary treatment of chronic inflammatory diseases. Two groups of fibrmomyalgic patients with similar hematological and clinical sypmtoms were blindly assigned to omega-3 or placebo supplementation for 5 weeks. At the of treatment fibromyalgig patients showed a sharp increase in eicosapentaenoic acid and a sharp reduction in arachidonic acid/ eicosapentaenoic acid and in positive tender points. No changes occurred in supeficial thermal and mechanical thresholds as well as in blood lipids, mood, sleep and clinical indicators. Results do not exclude that greater dayly amounts of omega-3 for longer periods of time might mitigate fibromyalgia symptoms ( 25 ). Sensitisation is a central neurobiological phenomenon caused by the facilitation, potentiation, and amplification of sensorial input in the central nervous system, a critical mechanism involved in fibromyalgia. It represents the core of the amplification of somatosensory sensation, a psychological dimension close to somatisation. Fibromyalgia patients show the highest total scores on the somatosensory amplification scale as compared to chronic pain patients, psychiatric patients and healthy subjects, although this high score is not associated with the somatisation disorder. Somatosensory amplification is common in fibromyalgia patients , while in the chronic pain group high somatosensory amplification values were found only in the presence of a somatisation disorder. Finally, fibromyalgia patients have the highest prevalence of somatisation disorder, even though it is not associated with somatosensory amplification (2).
Hormone basal levels have been studied in soccer players after 3, 12, and 24 weeks of training and agonistic matches. Testosterone and prolactin increased during the 3 weeks pre-season conditioning when athletes were submitted to intense physical activity. Later, prolactin further increased whereas testosterone recovered basal levels. ACTH was not affected, whereas cortisol was found elevated in the last two samples. Final estradiol increased in the last samples. Results suggest that the initial hormone modifications are a consequence of the intense physical training of the pre-seasonal conditioning. Since athletes displayed a constant level of fitness, it is suggested that other factors could have contributed in the later part of the agonistic season to the elevation in basal levels in cortisol, prolactin and estradiol, that are known to be elevated by stress (91). In a further study the possible factors affecting the hormonal changes during and after a football match were investigated in two different teams with a similar seasonal training intensity and levels of performance tested during a match against a team belonging to a lower rank league. In the first team ACTH cortisol and lactate increased during the whole match resuming basal levels 45 min after the end of the match. HGH , prolactin and blood glucose were found to be increased at half time. The second team performed an intense and long lasting warm-up before the match that elevated the lactate levels before the beginning of the match. ACTH did not change during the match but was decreased below warming-up levels at the end of the match , whereas lactated reached a peak at the end of warming up, gradually decreasing during the match. The plasma levels pattern modifications of the other hormones were similar to that of the first team. The general work load exerted during the matches was scored as medium in the first team and light for the second one. In conclusion, the differences in hormonal and metabolic parameters do not appear justified by the differences in the work load but rather to different motivational, environmental and emotional factors (83).
In teenage girl swimmers (age 13-18 years) hormone blood samples were collected during a training and competitions season at interval of 4, 12 and 24 weeks. Training intensity and competitions gradually increased through the season. ACTH gradually increased over the season whereas cortisol showed some oscillations, decreasing in sample 2, increasing in sample 3 and recovering basal level in sample 4. Prolactin increased in the last two samples, whereas estradiol basal levels were higher in post-puberal girls with respect to the pre-puberal ones, both groups displaying a decrease in sample 2 and 3 and a recovery in the last sample. Interestingly, post-puberal girls, that had been selected for their regular menstrual cycles, maintained their regularity throughout the season. The latter finding is an indication of the tolerability of the training program (90). Blood lactate levels provide an useful indication of the energy derived from anaerobic glycolysis during exercise. In swimmers lactate levels after competitions differ according exercise intensity , duration and sex. Results show that there is a positive relationship between swimming speed corresponding to 4 mmol/ 1 blood lactate and competition velocity in males at 200, 400 and 1500 m and in females at 400 and 1500. In conclusion, the analysis of individual lactate-speed relationship , obtained following a submaximal test, represents an useful tool in establishing the aerobic capacities necessary to take part to high level free-style competitions in middle and long distances (67). Swimming has been found to be characterized by a redistribution of blood towards central veins as an effect of the supine position, and water pressure and by heat loss without sweeting. Atrial natriuretic peptide plays an important role within the complex system regulating homeostasis of body fluids. It inhibits the plasma renin activity –aldosterone axis and the release of antidiuretic hormone. Its variation appears related to immersion rather than to the exertion of swimming. Results show that, following a 18 km long distance swimming competition , atrial natriuretic peptide plasma levels increase exerting an inhibitory effect on plasma renin activity –aldosterone axis and a modulatory role with regard to antidiuretic hormone (65). Testosterone exists in the plasma bound to sex-hormone-binding globulin, bound to albumin and free (only 2%). Therefore, the plasma concentrations of non sex-hormone-binding globulin testosterone represent the most sensitive indicator of androgen activity rather than T. In endurance training, work load must be constantly increased during the season to provide optimal stimuli for the process of adaptation , but intense training causes an alteration in homeostasis resulting in decreased performance. Male endurance swimmers were tested 6,12 and 24 weeks since the beginning of the season. Corticosterone levels increased after exercise, the effect being the highest in the second session. Total testosterone, testosterone/ sex-hormone-binding globulin ratio Free testosterone and non sex-hormone-binding globulin testosterone, free testosterone and non sex-hormone-binding globulin testosterone increased after exercise recovering basal level 1 hr after the exercise end. Considering also the different changes in the different forms of testosterone in different periods of the different sessions, it appears that non sex-hormone-binding globulin testosterone represents the best index of the metabolic response to exercise (62). In endurance swimmers, during different periods of the training season corresponding to different levels of aerobic performance, it is crucial to know the response of ACTH and GH to a submaximal swimming exercise . Tests were performed 6, 12 and 18 weeks after the beginning of the season in which the work load increased from the 7th to the 12th week, remaining constant afterwards while the aerobic performance continued to improve reaching the peak at the 18th week. Training did not affect resting levels of ACTH and GH. ACTH increased after the exercise that the effect was much lower in the last session, an indication of adaptation to the exercise intensity. GH increased after all sessions but the effect was much higher in the last session than in the other two. The increase in ACTH increase associated with the decrease in GH in response to submaximal exercise should lead to an enhancement of fatty acids utilization with a decreased utilization in glucose and amino acids, increasing protein synthesis and decreasing protein degradation, a further indication of physiological adaptation to exercise load (49).
At rest, branched chain amino acid , in response to functional requirements, are utilized by muscle fibres for protein synthesis. During prolonged intense exercise their degradation within the muscle is greatly increased , while plasma concentration is reduced. The effects of 1 hour continuous running performed at the same predetermined speed with and without (placebo) administration of branched chain amino acids were tested. For each athlete the running speed corresponded to the steady-state blood lactate accumulation previously determined. Blood samples were collected at 9 am, basal value, just before drinking the mixture, after 90 min before the running test, at the end of the running test and 1 hour afterwards. In the placebo group, following exercise, HGH, prolactin, ACTH, and cortisol increased , while testosterone decreased. After 1 hour ACTH, prolactin and HGH recovered basal levels , while cortisol remained elevated and testosterone decreased. Similar pattern of change were recorded in the experimental group at the end of exercise for HGH, prolactin, ACTH and cortisol. However, in the last sample HGH and prolactin displayed significant lower values than the corresponding placebo samples, testosterone was not modified by the running exercise and increased during the last hour recovery period. Thus, the branched chain amino acids administration before exercise affects anabolic hormones such as testosterone (73). After knee surgery most rehabilitation programs involve isokinetic training and most of muscle evaluation assessments have been performed with constant speed dynamometers. During testing, due to the limitations of the isokinetic apparatus, patients have to develop a remarkably muscle strength that is limited by the patients pain thresholds. In this study it is proposed a new procedure, the comparison of the performance in leg extension test and the response in the superficial electromyographic activity to total body vibration in the operated and non-operated leg. Results indicate that this new procedure is suitable for detecting the impairment as well as for monitoring the rehabilitation programs (5)