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A novel, computer-driven, dynamic-force detector was validated for use in measuring the formalin-induced agitation response. Intraplantar administration of formalin (0.25-5%) provoked a biphasic agitation response as measured with the automated system. The magnitude of both phases of the response increased with the intensity of the noxious stimulus. Morphine (1-5 mg/kg, s.c.) inhibited both phase...
It has been suggested that ageing may have a differential effect on C fibre-mediated protopathic/tonic pain versus epicritic/phasic pain perception mediated by Aδ fibres. The present study attempted to independently assess age-related changes in the function of Aδ- and C-nociceptive fibres by examining CO 2 laser-induced thermal pain thresholds before, during and after a compression block...
Rats and humans manifest elevated response thresholds to aversive stimuli during gestation and parturition. This pregnancy-associated antinociception is mediated, in part, by a spinal cord dynorphin/κ antinociceptive system. Simulating the maternal pregnancy blood concentration profile (in non-pregnant animals) of 17-β-estradiol (E 2 ) and progesterone (P) produces an opioid antinociception...
Although evidence is lacking, clinical experience suggests that pain stimulation acts as a respiratory stimulant and antagonises opioid-induced respiratory depression. The present study examined the effects of experimental pain stimulation on the ventilatory response to CO 2 and morphine-induced respiratory depression. Pain was induced by a modification of the Tourniquet Pain Technique and...
This study was conducted to determine the contribution of peripheral inputs from injured and intact afferent fibers to behavioral signs of neuropathic pain, using a previously developed neuropathic rat model. Neuropathic injury was produced by tightly ligating the left L5 and L6 spinal nerves; this procedure induced rats to display neuropathic pain behaviors in the ipsilateral hindlimb. The behaviors...
Lesions in the cingulate cortex have attenuated pain-related behavior in humans. We wished to evaluate an animal model of this effect by studying the effects of bilateral lesions within the medial frontal cortex, including rat cingulate cortex, on performance in 3 behavioral tests: the formalin, hot-plate, and tail-flick tests. Average hot-plate latencies, but not formalin test scores or tail-flick...
The action of lignocaine on nociceptive transmission in the spinal cord has been studied in vitro using ventral root potential (VRP) recordings from 10-12-day-old rat hemisected spinal cord preparations. Single-shock stimulation of a dorsal root at intensities sufficient to activate high-threshold C-primary afferent fibres elicited VRPs lasting for 15-20 sec in the corresponding ventral root. The...
Post-sympathectomy neuralgia is proposed here to be a complex neuropathic and central deafferentation/reafferentation syndrome dependent on: (a) the transection, during sympathectomy, of paraspinal somatic and visceral afferent axons within the sympathetic trunk; (b) the subsequent cell death of many of the axotomized afferent neurons, resulting in central deafferentation; and (c) the persistent sensitization...
Ro 15-8081, a substituted cyclohexanol hydrochloride, inhibits the re-uptake of norepinephrine and of serotonin. Its antinociceptive properties have been demonstrated in animals and then confirmed in humans after single-dose administration. The objective was to determine the analgesic efficacy and the safety of Ro 15-8081 in osteoarthritis of the hip and knee (femoro-tibial location) after multiple-dose...
Systemic phentolamine administration has been suggested as a diagnostic tool for identifying patients with sympathetically maintained pain (SMP) (Raja et al. 1991). The dose of phentolamine to produce adequate blockade of peripheral α-adrenoceptor function has, however, not been previously determined. In this study, the effects of two different doses of phentolamine on peripheral sympathetic vasoconstrictor...
In a human acid pain model, which uses continuous intradermal pressure infusion of a phosphate-buffered solution (pH 5.2) to induce localized non-adapting pain, the flow was adjusted to result in constant pain ratings of about 20% or 50% on a visual analog scale (VAS). Six volunteers in each group participated in 4 different placebo-controlled double-blind cross-over studies to measure rapidly evolving...
In humans, both nitric oxide (NO) and bradykinin, a naturally occurring algetic and a potent NO liberator, evoke pain from hand veins. The afferent innervation of these veins consists solely of polymodal nociceptors which are located close to the endothelium, a well-known source of NO, thus suggesting NO as a chemical link in nociception. Consistent with this hypothesis, our observations show that...
A model of deafferentation pain is provided by sectioning the sciatic and saphenous nerves in the rat and mouse. This procedure leads to self-mutilation of the denervated hindpaw (autotomy). A noxious stimulus to the denervated area before neurectomy is known to enhance the autotomy. To understand the mechanism underlying this enhancement by prior noxious stimuli, we examined the effects of intrathecal...
The aim of the investigation was to evaluate the prevalence, severity, and parents' management of children's pain following short-stay and day surgery. The subjects were 189 parents of children (2-12 years of age) who had undergone short-stay or day surgery. Parents completed a 3-day diary of their child's pain and the methods used to alleviate it. There were clear differences in pain reported...
Capsaicin is a pungent-tasting compound produced by plants in the Capsium family that activates a subset of primary afferent neurons associated with pain and thermoreception. Previous studies from dorsal root ganglion (DRGs) neurons suggest that many of capsaicin's physiological responses are a consequence of its activating a cation-selective current. To further characterize the responses to capsaicin...
The N-methyl-d-aspartate (NMDA) receptor is implicated in multiple aspects of pain processing by the central nervous system. However, the role of NMDA receptors in the endocrine and autonomic aspects of nociception remains uncertain. The present study examined the influence of the NMDA receptor antagonist, MK-801 (0.02-2.0 mg/kg, intracarotid), on the adrenal and autonomic responses to corneal stimulation...
The beliefs and expectancies of chronic pain patients have been shown to be critical cognitive facilitators or impediments to the recovery process. In the present study patients presenting to an outpatient pain center were classified according to their response to the questionnaire item Who do you think is at fault for your pain? . Patients were then grouped according to the responses employer...
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