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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Unilateral entrapment of half of the sciatic nerve in a ligature rapidly produces in rats bilateral hyperalgesia: decreased withdrawal thresholds to von-Frey hair touch and to noxious CO2 laser heat pulses and unilateral hyperpathic responses to a supra-maximal noxious heat pulse. These abnormal pain responses last many months and are very similar to those seen in humans with causalgia. In the present study we determined whether the underlying mechanism involves bilateral sensitization of primary afferent receptors. Since the responses of rats with partial sciatic injury to stimulation of rostral areas (forepaws, muzzle and auricles) were normal, we presume that the hyperalgesia at the contralateral hindpaw could not be due to receptor sensitization, but to rapid central plasticity. Moreover, since indomethacin did not prevent the bilateral hyperalgesia, we conclude that the causalgiform pain disorders seen in the ipsilateral hindpaw did not derive from receptors sensitized by prostaglandins.
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PMID:Lack of sensitization of primary afferent receptors by prostaglandins in a rat model of causalgic chronic pains. 321 4

Two cross-sectional studies were made of the recovery of tactile and pain sensitivity in subjects having skin flaps in the region of the chest and neck as a result of tumor excision. In experiment 1, stimuli ranging from 2.46 to 17.10 gm of force were delivered by von Frey hairs to the flaps and comparable normal sites in 35 subjects at times ranging from 1 month to 10 years after surgery. No subjects perceived stimuli of less than 11.80 gm, thermal, or moving touch applied to flaps, whereas 21 percent perceived 11.80 gm or greater force (judged as painful applied to normal skin). The results of experiment 2 showed that these findings were not due to visual information available to subjects. Possible explanations for the fact that these results are radically different from those reported in the literature are discussed.
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PMID:The recovery of sensory function following skin flaps in humans. 349 95

The effect of local skin cooling on the behavior of low- and high-threshold mechanoreceptive afferents innervating glabrous and non-glabrous skin was studied in microneurographic recordings on awake human subjects. Cooling with ice or ethyl chloride to a skin surface temperature below 10 degrees C caused a reduction of receptor sensitivity in 49 out of 52 studied low-threshold afferents. This effect was reversible upon warning but some reduction often persisted for a few minutes after normal skin temperature had been reached. The subjects' sensations of application and removal of von Frey hair stimuli were more resistant than had reappeared before the sensation of sustained pressure. This could be explained by shorter recovery times for fast than for slowly adapting units and by a relative preservation of the dynamic responses of the slowly adapting units. During the recovery phase some low-threshold mechanoreceptive afferents exhibited a transient 'spontaneous' discharge in the absence of external mechanical stimulation. The suppression of afferent C-fibre responses to needle strokes was more pronounced and long-lasting than the effect on A-fibre responses and largely paralleled the recovery of sensation of pain. It is concluded that the local anaesthetic effect of skin cooling is to a large extent explicable in terms of receptor desensitization although other mechanisms may contribute.
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PMID:Peripheral neural correlates of cutaneous anaesthesia induced by skin cooling in man. 357 12

Carrageenan was subcutaneously injected in the area innervated by the saphenous nerve. Part of the mechano-heat sensitive C-fiber receptors (CHM) located inside or at the border of the inflamed area showed an enhanced responsiveness to heat stimulation (sensitization). Those CMH units exhibited spontaneous activity; their mechanical thresholds (von Frey) were higher than those of not spontaneously active fibers. None of the units located outside of the inflamed area displayed sensitization. The data reveal that only part of the CMH units in a uniformly inflamed skin area shows signs of sensitization. Our results are compared to those obtained in other inflammatory processes. The relation to inflammatory pain and to hyperalgesia and the contribution of endogenous substances to sensitization of CMH units are discussed.
Pain 1987 Jun
PMID:The effect of carrageenan-induced inflammation on the sensitivity of unmyelinated skin nociceptors in the rat. 361 71

To determine whether tactile sensitivity of the normal skin is altered by suppression of sympathetic efferent activity, the effect of stellate ganglion block and epidural sympathetic block on touch threshold was studied. The study was performed on ten individuals with various chronic pain syndromes. Tactile sensitivity was measured in the normal skin area with the use of von Frey filaments and a two-alternative forced-choice procedure with a staircase presentation of touch stimuli. With stellate ganglion block, touch threshold decreased on the side of the block by 48.8 +/- 8.% (P = 0.002) without any significant change in the threshold on the healthy, nonblocked side (P = 0.003 for the difference between the sides). With epidural sympathetic block, touch threshold decreased to the same extent on the diseased and healthy sides, which were both affected by the block (46.2 +/- 11.4%, P = 0.027 and 47.7 +/- 12.5%, P = 0.032, respectively). The results show that sympathetic blockade increases tactile sensitivity. They also suggest that sympathetic efferent activity modulates the function of tactile receptors. It is hypothesized that the sympathetic modulation makes tactile receptors less sensitive to touch, less specific, and probably more prone to code tactile stimuli in such a way that the brain recognizes this code as pain.
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PMID:Sympathetic blockade increases tactile sensitivity. 368 97

Sixty patients with essential trigeminal neuralgia underwent selective percutaneous thermocoagulation of the gasserian ganglion. Immediate and long-term modifications of pain and tactile facila sensitivity, recurrences of pain, and occurrences of facial paresthesias were evaluated. Pin-prick and von Frey hair tests and somatosensory-evoked potentials were used to study facila sensitivity. Patients with mild alterations of sensitivity-treated with low temperatures of coagulation (60 degrees-70 degrees C)--had a lower incidence of paresthesias, although a higher risk of recurrence. Patients with severe alterations of sensitivity--a consequence of a temperature of coagulation above 70 degrees C--had a high incidence of paresthesias and a low risk of recurrence. In our opinion, the first kind of results are better.
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PMID:Alterations of facial sensitivity induced by percutaneous thermocoagulation for trigeminal neuralgia. 660 54

The order of sensory recovery (the first appearance of each sensory modality in the amputated digit) and the speed of sensory recovery in the amputated digit were recorded in 74 replanted digits in which both digital nerves had been severed and repaired primarily. The order of sensory recovery was measured by Frey hairs to determine pressure (30 gm) and touch (2 gm). Pain (5 gm) was measured by an algesiometer and cold (0 degree C) and warmth (50 degrees C) were measured by a thermometer (Yufu Seiki Co., Ltd.). Perspiration was measured by the bromophenol blue printing method. The mean times of the appearance of sensibility in the amputated digits were: pressure, 9.8 weeks; touch, 11.6 weeks; pain, 13.4 weeks; cold, 15.3 weeks; warmth 16.8 weeks; and perspiration, 26.9 weeks. The speed of sensory recovery was a measurement of the first appearance of sensibility in the amputated digit to the restoration of sensibility to the fingertip. The speed of sensory recovery for touch and pain was calculated by dividing the number of months required for sensory recovery by the distance from the replant level to the fingertip. The mean speed of sensory recovery for touch was 14.0 mm per month, and for pain it was 13.2 mm per month.
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PMID:A clinical study of the order and speed of sensory recovery after digital replantation. 663 Sep 29

Pain intensity and the importance of pain for the cancer patient depend on a variety of individual factors and show considerable divergence (Bonica and Ventafridda 1979). They are greatly influenced by the enigma of the cancer disease as well as the consequential psychiatric problems (Frey 1980). An effective neurological analysis of the cancer pain, although demanding for the physician, is important for further specific diagnostic procedures and for the indication of appropriate therapy. Sometimes thorough neurological examination can lead to the first diagnosis of the carcinoma; when there is already evidence of metastases, the unfavorable prognosis can be made at the same time.
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PMID:Analysis of cancer pain by the neurologist. 669 6

In the present work responses of intradental nerve fibres to stimuli that induce fluid flow in dentinal tubules as well as to direct mechanical irritation of the exposed pulp were studied on 9 young adult beagle dogs. Under pentobarbitone anesthesia 31 single functional intradental fibre units were dissected from the mandibular nerve. Stimuli were applied to the lower left canine tooth. Exposed dentine surface was irritated by scraping, air blasts and dry absorbent paper and the pulp mechanically with a von Frey hair. Ten fibre units responded to stimulation of dentine. Six of them were also tested with mechanical irritation of the pulp and were all responsive. Fifteen of twenty fibres responded to mechanical stimulation of the pulp. The mechanosensitive nerve fibres were all A-type according to conduction velocities (mean 25.6 +/- 8.1 (SD) m/s). It is concluded that there exist mechanosensitive intradental A-nerve fibres in the dog which are activated by stimuli that induce fluid flow in dentinal tubules. Nerve fibres of this type could be responsible for dentine sensitivity in man. Consequently, the present study gives support to the hydrodynamic hypothesis of dentine sensitivity. Moreover, mechanosensitive nerve fibres could also be responsible for the pain symptoms of pulpal inflammation, because pulpitis may also create suitable circumstances for their activation.
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PMID:Responses of intradental nerve fibres to stimulation of dentine and pulp. 713 9

Percutaneous recordings from more than one hundred single C fibres have been performed in the radial nerve of conscious human subjects. All these fibres belong to the poly-modal C nociceptor group, being excited by mechanical and thermal and also by chemical stimulation. Conduction velocities showed a monophasic distribution with a mean value of 0.86 m/s (SD: 0.17). The mechanical threshold, measured with von Frey hairs, varied between 2.3 and 13.1 g. The receptive field was circular or elliptical; for 33 units the mean axes were 6 mm and 7 mm. Mechanically evoked C fibre discharge even up to more than 10 spikes/s was not necessarily accompanied by pain sensation. Nettle sting evoked an irregular C fibre discharge (maximum 10 spikes/s) accompanied by a pricking and burning sensation; the sensation of itch which was sometimes reported, was not correlated with the discharge frequency. C fibre activation by a chemical irritant (paint remover) also evoked an irregular discharge (maximum 3 to 6 spikes/s), accompanied by pricking and burning pain sensation. The C threshold for radiant heat usually lay below the subject's pain threshold. Increasing skin temperature produced increasing neural firing rate. The mean spike frequency rarely exceeded two spikes/s even with stimuli evoking strong heat pain. The occurrence of subjective heat pain response could be as well predicted from th C fibre spike frequency as from the skin temperature. It is concluded that nociceptive C input provoked by thermal or chemical stimuli correlates well with pain sensation. However, similar C input provided by mechanical stimulation which activates also A beta mechanoreceptors, did not necessarily produce pain sensation.
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PMID:C nociceptor activity in human nerve during painful and non painful skin stimulation. 728 47


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