Bibliography

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).

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 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)

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).

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).

pendent (27).

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  7^th to the 12^th week, remaining constant afterwards while the aerobic performance continued to improve reaching the  peak at the 18^th 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)