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

We investigated the ability of human nociceptive primary afferent neurons to encode mechanical pain and to produce vasodilatation. Pain was induced by shooting a light metal cylinder (0.3 g) at different velocities (6-18 m/sec) perpendicularly against the hairy skin of the hand. When single impact stimuli were applied, monotonically increasing stimulus-response functions were obtained in 10 psychophysical experiments using magnitude estimation techniques. In 35 microneurographic experiments nine unmyelinated afferents were recorded from the superficial radial nerve. All units responded readily to impact stimulation even at stimulus intensities that were not rated as painful. However, there was a close linear correlation between the number of action potentials evoked from the nociceptors and the psychophysical magnitude estimates of the perceived sensation or the stimulus intensity. This was also reflected by a corresponding increase of neurogenic vasodilatation. While two thin myelinated afferents displayed qualitatively similar responses 12 low-threshold mechanosensitive afferents (4 rapidly adapting, 5 slowly adapting type 1, 3 slowly adapting type II) failed to encode the intensity of the applied impact force and often became desensitized. This indicates that the total number of action potentials is the determinant of the magnitude of mechanical pain and the associated vasodilatation following single brief stimuli. By contrast, the close correlation between nociceptor activity and sensation changed when trains of mechanical impact stimuli (five stimuli of constant intensity, intratrain frequency of 1/32 to 2 Hz) were applied. Magnitude estimates of pain intensity were frequency dependent and stimuli with short interstimulus intervals were perceived as more painful than those delivered with long intervals. However, the total number of action potentials evoked from C-fibers was higher at longer interstimulus intervals than shorter intervals, thus yielding a negative correlation between the magnitude estimates of the perceived painful sensation and the number of action potentials elicited from nociceptive afferents. This suggests that temporal summation of the nociceptive discharge at central neurons becomes increasingly more important for the sensory discriminative experience of pain evoked by repetitive stimulation. We conclude that human nociceptive C-fibers signal brief noxious mechanical stimuli by the total number of action potentials evoked during a short period of time. However, with repetitive stimulation the total number of action potentials evoked from nociceptors is less important for evoking pain and temporal summation of the nociceptive primary afferent discharge becomes the crucial factor for signaling the magnitude of sensation.
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PMID:Differential ability of human cutaneous nociceptors to signal mechanical pain and to produce vasodilatation. 812 68

In the early phases of HIV infection, the oral cavity may develop erythematous and pseudomembranous candidiasis, oral hairy leukoplakia (OHL), necrotizing ulcerative periodontal disease, Kaposi's sarcoma, and infections with Herpes simplex viruses, cytomegalovirus, Epstein-Barr virus, and Varicella zoster virus. The leading oral infections are candidiasis and OHL. The most common oral form of candidiasis is pseudomembranous, which appears white and milky and can be easily removed from the mucosal surface. After removal, this surface will bleed and be raw. OHL forms a white, corrugated (hairy) 1 m to 2 cm patch, generally on the lateral borders of the tongue. OHL rarely occurs in persons not infected with HIV. HIV-positive people often experience considerable periodontal destruction, causing much pain. They may also have atypical gingivitis. Painful, indolent oral ulcers are often on the tongue, lip, gingiva, and esophagus. Almost everyone with advanced HIV infection is seropositive for cytomegalovirus. Molluscum contagiosum lesions in HIV-infected persons are larger and more numerous than those in children. Various cutaneous or noncutaneous noninfective conditions (e.g., psoriasis and vasculitis) are also more common in HIV-infected persons. Possible agents to control candidiasis are fluconazole and chlorhexidine oral rinse. Topical or systemic corticosteroids may control aphthous-like ulcers. The drug acyclovir may control herpes virus and other viral infections. If acyclovir is ineffective, desciclovir, ganciclovir, or foscarnet are possible alternatives. Papilloma virus lesions can be treated with cryosurgery, laser therapy, or surgical excision. Radiotherapy, chemotherapy, and interferon are treatments for Kaposi's sarcoma. Aspirin and other nonsteroidal anti-inflammatory drugs may be contraindicated in patients with thrombocytopenia or who are on corticosteroid therapy.
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PMID:AIDS and the gateway of the body. 820 72

Thirty-two healthy human subjects provided thresholds for the perception of slight and moderate heat pain. Four body sites were tested bilaterally: thenar eminence of the hand, plantar surface of the foot, dorsolateral forearm, and lateral calf. Thresholds for the glabrous skin of the hand and foot were significantly greater than thresholds for the hairy skin of the arm and leg, the average difference being 1.3 degree C. Laterality was not a statistically significant factor. Thresholds increased progressively over 2-4 weeks of repeated testing, resulting in values averaging 0.6 degree C higher in the later sessions. The difference between moderate and slight pain thresholds averaged 1.1 degree C, and was consistent across body sites and with repeated testing. The threshold values were normally distributed across subjects. Considerable intersubject variability was observed for both slight and moderate pain thresholds, more so on glabrous than on hairy skin sites. In comparison, the distribution of right-left difference values was narrower, demonstrating less intrasubject versus intersubject variability. The highly significant difference in thresholds between glabrous and hairy skin sites demonstrates the importance of skin type for heat pain sensitivity. In contrast, there was no significant difference in heat pain sensitivity between comparable sites on the upper versus lower extremities, or between left and right sides.
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PMID:Body site variation of heat pain sensitivity. 831 Jul 82

The scientific literature suggests that barefoot activity may be beneficial. There is a current trend in recreational barefoot activity in children and adults, and barefoot running among athletes. Although the type of skin over most of the body (hairy skin) seems to be easily injured by painful abrading loads, little is known about protection provided by plantar sensory feedback against damage from excessive wear during barefoot locomotion. To evaluate this, we administered a volley of 35 painful abrading loads to glabrous and hairy skin sites over a 5-min period, and examined its effects for signs of cutaneous injury in a sample of 12 normally shod healthy male subjects. Compared with hairy skin of the thigh, plantar skin required approximately 600% greater abrading loads to reach pain threshold. Furthermore, painful stimulation produced visible redness and hypersensitivity in all subjects at the hairy skin site 24 hr after stimulation, whereas only 8.3% reported hypersensitivity and none showed erythema at the plantar area 1 day later. We found that plantar skin possesses a higher pain threshold to abrading stimuli than hairy skin. In fact, loading of the plantar area was limited to innocuous levels due to intolerable pain. We conclude that plantar skin is well protected through sensory feedback from abrasive injuries when barefoot. This information combined with previous reports suggests that risk of injury when normally shod individuals perform barefoot locomotion should be low.
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PMID:Protective sensation of the plantar aspect of the foot. 840 51

Forty-seven patients who underwent splenectomy for splenomegaly > or = 1000 g were studied retrospectively. There were 29 men and 18 women of mean age 56 (range 19-87) years. Haematological malignancy was the most common disorder (42 patients). The main indications for splenectomy were cytopenia (20 patients), diagnosis (14), initial treatment of leukaemia (eight), pain (four) and spontaneous rupture (one). Thirteen patients underwent an associated surgical procedure. One patient died (mortality rate 2 per cent) and 12 (26 per cent) had postoperative complications. The advantages of splenectomy included histopathological diagnosis in 13 of 14 patients with splenomegaly of unknown origin, effective initial treatment in prolymphocytic and hairy cell leukaemia, definitive relief of pain in all affected patients, and long-term improvement of cytopenia in most.
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PMID:Splenectomy for splenomegaly exceeding 1000 grams: analysis of 47 patients. 847 44

While age-related sensory deficits have been demonstrated for the senses of vision, audition, and the chemical senses, reports have differed with regard to changes in painful and non-painful thermal sensation. One hundred and seventy-nine healthy, community-dwelling individuals aged 20-89 years rated threshold and suprathreshold warming, cooling, and painful stimuli delivered to glabrous (upper lip) and hairy (chin) sites of the face in three separate testing sessions. Threshold measures were determined by the Method of Limits. Suprathreshold stimuli were assessed by a cross-modality matching procedure and a Pooled Adjacent Violators Algorithm-based analysis. The analyses of the effect of age on the threshold and suprathreshold measures of sensory performance yielded disparate findings. There are modest changes in warming and cooling perception with increased age, but pain perception is relatively unaffected. There is a slight diminution in threshold and suprathreshold thermal performance with increasing aging.
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PMID:Aging effects on the perception of noxious and non-noxious thermal stimuli applied to the face. 869 74

Formalin injected subcutaneously into the paw is a frequently used pain assay; it evokes an initial period of licking and flinching followed by a period of quiescence and last by a second period of intense and protracted licking and flinching. The prominent second phase is believed to reflect the development of a central (spinal cord) facilitation. This conclusion is based on the assumption that formalin evokes an initial burst of activity in fine afferent fibers, followed by prolonged low levels of activity in C fibers. Detailed reports substantiating this essential assumption have not been published. Thus, we recorded in situ from single sural nerve fibers, identified by their conduction velocity and modality, in the barbiturate anesthetized rat. Following formalin (2.5%, 50 microliters) injection into their receptive fields, phase-1 activity was prominent in A beta and A delta fibers as well as in high-threshold C nociceptive afferent fibers. Phase-2 activity was observed in A delta fibers with receptive fields in hairy skin and in all mechanically sensitive C fibers. Mean phase-2 activity in these fibers was 1/2-2/3 of the magnitude achieved in phase 1. Mechanically insensitive fibers and A delta and C fibers with receptive field centers outside of the injection zone began firing 15 min or more post-injection and would contribute to phase-2, but not phase-1, behavioral activity. Intravenous infusion of low doses of lidocaine yielding plasma levels of 3.6-7.9 micrograms/ml administered during phase 2 blocked formalin-evoked activity in primary afferent fibers in a dose-related fashion without blocking either electrically or mechanically evoked activity. Effective plasma doses were comparable to those found to relieve neuropathic pain. These data indicate that phase 2 in the formalin test is more closely related to ongoing afferent input than had previously been thought.
Pain 1996 Feb
PMID:Formalin-evoked activity in identified primary afferent fibers: systemic lidocaine suppresses phase-2 activity. 874 Jun 13

We compared the effect of skin temperature on the critical threshold temperature eliciting heat pain with the effect of skin temperature on the response latency to the first heat pain sensation in healthy human subjects. Also, we determined the effect of the duration of a heat stimulus ramp on pain threshold. Furthermore, we determined the effect of skin temperature on mechanically induced pain. We found that the latency to the first pain sensation induced by a radiant heat stimulus was significantly decreased with an increase in the skin temperature (25-35 degrees C). However, independent of the rate of the stimulus rise (3-10 degrees C/s) and independent of the stimulus location (hairy vs glabrous skin), the threshold temperature for eliciting the heat pain sensation, determined with a contact thermostimulator, was not changed by a change in the skin temperature in the same subjects. With a fast rate of stimulus rise, a higher pain threshold was obtained than with a slow rise of stimulus temperature. However, this difference was found only with subject-controlled ascending stimuli (method of limits) but not with experimenter-controlled, predetermined stimulus ramps (method of levels). The heat pain threshold was higher in the glabrous skin of the hand than in the hairy skin of the forearm. With increasing stimulus duration (2.5-10 s), the threshold temperature eliciting the heat pain sensation was significantly decreased. The mechanically induced pain threshold was not influenced by the skin temperature. The results indicate that the critical temperature for eliciting heat pain is independent of the skin temperature in humans. However, a change in skin temperature is an important source of an artefactual change in heat pain sensitivity when the radiant heat method (latency or energy) is used as an index of pain sensitivity. With a method dependent on reaction time (the method of limits), the heat pain threshold was artefactually increased, with fast rates of stimulus rise due to the long delay of slowly conducting heat pain signals in reaching the brain. With an increase in the duration of the heat stimulus, the critical temperature for eliciting pain sensation was significantly decreased, which may be explained by central neuronal mechanisms (temporal summation).
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PMID:Influence of skin temperature on heat pain threshold in humans. 882 89

In 8 healthy subjects we have recorded cerebral evoked potentials and reaction time (RT) to CO2 laser stimulation of the hairy and glabrous skin at low and high stimulus intensities, corresponding to subjective reporting of detection and pain, respectively. At each intensity we were able to identify an evoked potential; the latencies of the major vertex positive (VP) components fell into 2 distinct populations 320 +/- 30 (VP300) and 778 +/- 80 (VP800) which did not differ between stimulation sites. The frequency of the VP300 responses was greatest in the high stimulus conditions and lower in the low stimulus conditions whilst the opposite was true for the VP800 responses. BImodal distributions of RT were seen at both stimulus intensities. In a further group of of 10 subjects we recorded the latency shift of the vertex negativity following proximal and distal stimulation of hairy skin of the left upper limb and derived conduction velocities for the VP300 (13.21 +/- 2.8 m/sec) and VP800 (1.26 +/- 0.29 m/sec) responses. These results suggest that, following CO2 laser stimulation of both hairy and glabrous skin, two different fibre populations are activated. The VP300 responses appear to be related to A delta activation, while the characteristics of the VP800 responses are consistent with activation of thermoreceptors mediated by C fibres.
Pain 1996 Jul
PMID:CO2 laser activation of nociceptive and non-nociceptive thermal afferents from hairy and glabrous skin. 885 34

1. Fifty-five C-polymodal nociceptors innervating hairy skin in human volunteers were tested for discrete stimulus-response properties through microneurography. 2. All fifty-five units were responsive to mechanical and heat stimuli. Twenty-two (40%) of these exhibited an additional response to noxious low temperature. The twenty-two mechano-heat-cold nociceptors displayed similar receptor responses to heat and mechanical stimuli, and conduction velocity, as those of the pure mechano-heat C-polymodal nociceptors. 3. Low temperature stimuli between 19 and 0 degree C evoked responses at low discharge frequency (0.4 +/- 0.22 impulses s-1, mean +/- S.E.M.) in the twenty-two units sensitive to such energy. These units displayed a tendency to decrease their discharge after a few seconds of steady stimulation. 4. Three units tested with a freezing stimulus responded with relatively vigorous discharge, which never exceeded the maximal discharge frequency elicited by either mechanical or heat stimuli. One of these units became sensitized to heat after the freezing challenge. 5. It is concluded that a subpopulation of C-polymodal nociceptors is sensitive to noxious low temperature and may thus contribute to the determination of cold pain. The same type of primary afferent is probably one mediator of the symptom cold hyperalgesia in peripheral nerve disease.
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PMID:C-polymodal nociceptors activated by noxious low temperature in human skin. 896 Nov 96


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