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Biomedical subjects

R Melzack

Publications and source records attributed to R Melzack.

At least 73 records · Page 4Linked to original sources
PubMed1987

Low-back pain during labor.

Earlier studies have shown that labor pain is highly variable in intensity and spatial location. Most women feel pain predominantly in the abdominal area whereas others complain about severe back pain. In addition to the pains associated with contractions, many women report continuous low-back pain. This study used the McGill Pain Questionnaire to examine each type of pain. Women during labor also tracked their perceived pain levels at the same time that contractions were registered on cardiotachographic records. The results show that continuous low-back pain is severe and is reported by about 33% of women during labor. It is described as being qualitatively different from the pains associated with uterine contractions. The pain of contractions felt in the back is often reported as "riding on" the continuous low-back pain so that both together may reach "horrible" or "excruciating" intensities. Continuous low-back pain is probably caused by the distention and pressure on adjacent visceral and neural structures in the peritoneum, in contrast to the rhythmic pains that are clearly related to contractions of the uterus. It is possible that each of these major kinds of pain may be controlled by different anesthesiologic and psychologic procedures.

Abdomen↗
PubMed1987

Analgesia produced by injection of lidocaine into the lateral hypothalamus.

The local anesthetic lidocaine was injected into the lateral hypothalamus (LH) of awake, freely moving rats immediately prior to pain testing with either the formalin or the foot-flick test. Regional anesthesia of the LH resulted in a significant bilateral reduction of pain scores in the formalin test but had no effect in the foot-flick test. The decreased pain in the formalin test was not due to the diffusion of lidocaine into areas surrounding the LH or other possible artifacts. The results provide further evidence of hypothalamic involvement in pain perception and indicate that different neural systems subserve different types of pain.

Animals↗
PubMed1986

Habenular stimulation produces analgesia in the formalin test.

Electrical stimulation of the habenula produces a striking reduction of continuous, formalin-induced pain in the rat. The analgesia occurs at current levels which do not appear aversive and persists for variable durations, ranging from 1 to 21 min in this experimental situation. The effect is not blocked by subcutaneous administration of a large dose of naloxone prior to the stimulation, indicating that it is not dependent on an opiate-sensitive system. Stimulation of the adjacent paraventricular nucleus of the thalamus was either aversive or had no effect on the pain scores. The anatomical connections of the habenula suggest that it may mediate the interaction of limbic forebrain structures with midbrain structures known to play a role in pain and analgesia.

Animals↗
PubMed1986

Autotomy after nerve sections in the rat is influenced by tonic descending inhibition from locus coeruleus.

This study examined the role of descending brainstem inhibition on autotomy (self-mutilation) produced by neurectomy, and on the enhancement of autotomy by an injury prior to denervation. Autotomy after sciatic and saphenous nerve sections was examined following lesions of the locus coeruleus (or sham lesions) in rats which were either uninjured or previously injured by an injection of formalin into the hindpaw. The prior injury of the paw produced a significant increase in autotomy which occurred earlier in rats with lesions of the locus coeruleus than in the sham controls. The locus coeruleus lesion by itself also produced an enhancement of autotomy. These results suggest that self-mutilation following neurectomy, and possibly its enhancement by prior injury, are subject to tonic inhibition due to descending controls from the locus coeruleus.

Animals↗
PubMed1986

Autotomy following sciatic and saphenous nerve sections: sparing of the medial toes after treatment of the sciatic nerve with capsaicin.

Autotomy, or self-mutilation of the foot following sciatic and saphenous nerve lesions, was examined in rats after pretreatment of the sciatic nerve with capsaicin. This pretreatment produced an alteration in autotomy behavior which resulted in the sparing of the medial side of the foot. The effect occurred following a long (12-week) pretreatment-test interval, but not after shorter (1- and 4-week) intervals. The effect also depended on the successive transecting of the saphenous and sciatic nerves. Sparing of the medial side of the foot occurred only when the saphenous nerve was transected at the time of the sciatic nerve treatment with capsaicin. Because the side of the foot innervated by the saphenous nerve was spared by treating the sciatic nerve with capsaicin, we suggest that capsaicin alters the course of autotomy by preventing collateral innervation of the saphenous region by the intact sciatic nerve during the pretreatment-test interval. The fact that this occurs only after a 12-week interval suggests that capsaicin's effect on collateral innervation is a gradual process that requires a long time to develop.

Animals↗
PubMed1986

Procedures which increase acute pain sensitivity also increase autotomy.

Rats typically display self-mutilation (autotomy) of a paw that has been denervated by transection of the sciatic and saphenous nerves. The cause of autotomy, however, is not known. It may be due to hyperesthesia (comparable to that seen in humans after peripheral nerve injury) or anesthesia (as an attempt to shed an insensate appendage). The present study tested the assumption that if autotomy is produced by pain, then procedures that normally augment the expression of pain should enhance autotomy after transection of peripheral nerves. Groups of rats were subjected to procedures known to produce an increase in pain sensitivity: (i) prior heat injury of either the ipsilateral or contralateral paw; (ii) systemic injection of noradrenaline and the monoamine oxidase inhibitor, pargyline; and (iii) intrathecal administration of substance P. The results showed that each of these procedures produced an increase in the level of autotomy. These results strongly suggest that autotomy is due to a sensory phenomenon which, in terms of human experience, would be described as pain or dysesthesia.

Animals↗
PubMed1985

Morphine injected into the habenula and dorsal posteromedial thalamus produces analgesia in the formalin test.

Microinjection of morphine into the area of the habenula and dorsal posteromedial thalamus (H-PMT) produces analgesia for tonic pain as measured by the formalin test in the rat. Control injections of morphine into sites near the H-PMT result in less or no reduction in pain, indicating that the analgesia observed is probably due to a site of action within the H-PMT rather than at surrounding neural structures. The analgesia is fully developed by the first time of testing, 10-16 min following the microinjection, and is completely reversible by naloxone, an opiate antagonist. The analgesia recorded is most likely due to morphine's action on the habenula, parafascicular or paraventricular nucleus of the thalamus, or a combination of these structures.

Animals↗
PubMed1985

New approaches to measuring nausea.

Valid measures of nausea are needed to evaluate the various treatments used to counter the nausea produced by chemotherapy. The overall nausea intensity (ONI) produced by 17 chemotherapy drugs was estimated by 17 physicians and 8 nurses, and 25 patients undergoing chemotherapy described the subjective qualities and ONI of their nausea on a modified form of the McGill Pain Questionnaire. The scores for the affective and miscellaneous categories of words in the questionnaire were found to correlate significantly with the physicians' and nurses' ONI estimates. The results formed the basis for the Nausea Questionnaire, which provided three indices of nausea: a nausea rating index (NRI), ONI and intensity of nausea according to a visual analogue scale (VAS). All three indices correlated significantly with the physicians' and nurses' ONI estimates and were significantly intercorrelated. All three also provided significant differences when the scores of patients who had received cisplatin or 5-fluorouracil were compared. The results indicate that the Nausea Questionnaire provides three valid indices of the subjective experience of nausea.

Adult↗
PubMed1985

Increased pain sensitivity following heat injury involves a central mechanism.

This study presents evidence for a central mechanism of hyperalgesia by showing that heat injury causes an increase in pain sensitivity even if the injured region is denervated shortly after injury. Increased pain sensitivity was demonstrated by increased autotomy following total nerve sections in an injured limb, and by reduced foot-withdrawal latencies in the paw contralateral to an injury.

Animals↗
PubMed1984

Unilateral analgesia produced by intraventricular morphine.

Morphine injected into the lateral ventricle of the rat produced unilateral analgesia in the formalin test, which involves continuous, moderate pain. In contrast, analgesia was produced bilaterally in the foot-flick test which involves brief, rapidly rising pain. In the formalin test, intraventricular morphine produced analgesia in the ipsilateral but not the contralateral hindpaw. Analgesia was achieved with relatively low doses of morphine (2.5-10.0 micrograms) in the formation test while very high doses (50-200 micrograms) were necessary to produce analgesia in the foot-flick test. These results add to other data indicating that different neural mechanisms underlie opiate analgesia in different types of pain. Moreover, they indicate that, in the formation test, the neural mechanisms of morphine analgesia are somatotopically organized and that forebrain structures are likely to be involved.

Animals↗
PubMed1984

Behavioral evidence in rats for a peptidergic-noradrenergic interaction in cutaneous sensory and vascular function.

Cutaneous sensory and vascular function was examined following application of capsaicin to the sciatic nerve and systemic injection of guanethidine. Together the two drugs produced a reduction in sensitivity to heat-pain, inflammatory pain (formalin test), tactile stimulation and skin temperature of the foot that exceeded the effects of either drug alone. The inflammation produced by an injection of formalin to the plantar surface of the hind paw was reduced equally by capsaicin or capsaicin + guanethidine. Cold sensitivity and inflammation produced by yeast injection were unaffected by all treatments. The data imply a peripheral interaction between peptidergic and noradrenergic systems with significant functional implications that may be important in the pathology of familial dysautonomia.

Animals↗
PubMed1984

Single nerve capsaicin: effects on pain and morphine analgesia in the formalin and foot-flick tests.

Application of capsaicin to the sciatic nerve reduces responsiveness to pain in the foot-flick test which examines brief, threshold-level pain. The purpose of the present study was to determine if a similar reduction occurs in the formalin test which examines suprathreshold, deep pain that persists for several hours. The sciatic nerve on one side in the rat was exposed and soaked for 15 min in a solution of capsaicin and the saphenous nerve was ligated and cut. The operated foot was tested for sensitivity to pain in the formalin and foot-flick tests 2 days to 12 weeks later both with and without morphine. The capsaicin treatment produced a substantial reduction in sensitivity to foot-flick heat pain at all times after surgery. In the formalin test, the effects were small and tended to suggest that the rats felt more rather than less pain. The capsaicin treatment markedly reduced the sensitivity of formalin test pain to morphine. This effect appeared about one week after surgery and persisted for 12 weeks. The results suggest that capsaicin-sensitive unmyelinated afferents play a role in the threshold-level, non-damaging heat pain, but are not involved in pain resulting from tissue damage. However, these afferents appear to be important for the spinal action of morphine on this type of pain.

Analgesia↗
PubMed1984

Severity of labour pain: influence of physical as well as psychologic variables.

The role of physical factors in the severity of labour pain has been neglected. The amount of cervical dilation, the frequency of the contractions, the woman's height and usual weight before the pregnancy and other physical factors were therefore examined in relation to the intensity of labour pain in 141 primiparous and 99 multiparous women. In general, pain increased gradually during labour in both groups of women, though the severity of the pain was lower in the women who had received prepared childbirth training than in those who had not. Although the average pain scores in this study were high, there were striking individual differences, some women having extremely severe pain and others having almost none. The pain scores in both groups of women were significantly correlated with the ratios of the women's usual weight to height. In the multiparous women the scores were also correlated with the woman's usual weight and the baby's weight but not with the woman's weight gain during pregnancy. Thus, the results show that physical as well as psychologic factors contribute to the severity of labour pain.

Adolescent↗
PubMed1984

Auriculotherapy fails to relieve chronic pain. A controlled crossover study.

Enthusiastic reports of the effectiveness of electrical stimulation of the outer ear for the relief of pain ("auriculotherapy") have led to increasing use of the procedure. In the present study, auriculotherapy was evaluated in 36 patients suffering from chronic pain, using a controlled crossover design. The first experiment compared the effects of stimulation of designated auriculotherapy points, and of control points unrelated to the painful area. A second experiment compared stimulation of designated points with a no-stimulation placebo control. Pain-relief scores obtained with the McGill Pain Questionnaire failed to show any differences in either experiment. It is concluded that auriculotherapy is not an effective therapeutic procedure for chronic pain.

Adult↗
PubMed1983

Effects of cholinergic and dopaminergic agents on pain and morphine analgesia measured by three pain tests.

The effects of several cholinergic and dopaminergic agents on pain and morphine analgesia were assessed using three pain tests. These tests--tail-flick, hot-plate, and Formalin--allow comparison of the effects of different noxious stimuli and different motor responses. Each pain test yielded a unique constellation of cholinergic and dopaminergic influences, suggesting that variation of stimulus and response parameters can change the functional expression of cholinergic and dopaminergic systems related to pain processing. Significant analgesia was observed in the Formalin test, compared with the saline control, after administration of choline (30 or 60 mg/kg), atropine (2 mg/kg), mecamylamine (2 mg/kg or 10 mg/kg), or apomorphine (0.3 or 8 mg/kg). No analgesic effects in this test were observed after atropine (10 mg/kg) or pimozide (0.125 or 0.5 mg/kg). In contrast, there was no evidence of analgesia produced by any of these drugs, in the doses given, in the hot-plate test, and only apomorphine (8 mg/kg) produced analgesia in the tail-flick test. When these cholinergic and dopaminergic agents were administered to rats after an injection of 2.5 mg/kg morphine, which by itself has been shown not to produce analgesia in any of the tests, a general pattern of facilitation was observed in the Formalin test but not in the tail-flick or hot-plate tests. Facilitation was produced by choline, atropine, mecamylamine, apomorphine, and pimozide (at 0.5 mg/kg but not 0.125 mg/kg). The data suggest that differences in the type of noxious stimulation and in the motor responses required in various pain tests are crucial in determining the observed pharmacologic profile of pain and opiate analgesia.

Animals↗
PubMed1983

Transcutaneous electrical nerve stimulation for low back pain. A comparison of TENS and massage for pain and range of motion.

Patients with acute or chronic low back pain were treated in a double-blind study that compared transcutaneous electrical nerve stimulation at intense levels and gentle, mechanically administered massage. Transcutaneous electrical nerve stimulation produced significantly greater pain relief, based on two measures of the McGill Pain Questionnaire, and significant improvement in straight leg raising. There were no significant differences between the two groups in backflexion scores. Pain-relief scores and range-of-motion scores were significantly correlated. The results indicate that pain-relief scores provide valuable information and can easily be obtained from patients for whom pain is a major symptom.

Back Pain↗