Pain
-
An experimental arthritis of the knee joint resulted in limping, guarding, and an increased response to heat stimuli (heat hyperalgesia). Spinal administration of the non-N-methyl-D-aspartate (non-NMDA) antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), significantly reduced the degree of peripheral inflammation, thermal and behavioral manifestations of arthritis. NMDA antagonists had no effect on the inflammation but did prevent the development of the heat hyperalgesia. Thus, central non-NMDA receptors play a major role in the development of peripheral inflammation while both non-NMDA and NMDA receptors are involved in the development of heat hyperalgesia.
-
Cold stimuli of varying intensities were randomly applied to upper middle incisors of 12 healthy young subjects for a mean duration of 2 min by individually adapted thermodes the temperatures of which ranged from +30 degrees C to -30 degrees C. The subjects were asked to rate the magnitude of their pain sensations during application of the stimuli by means of a linear potentiometer according to a category scale. After each stimulus, they were asked to describe the quality of their pain sensations. ⋯ This was described as a dull, burning pain which was difficult to localize. The human pain ratings are compared to recordings of intradental nerve fibres in the cat and, under the assumption that the response behaviour of human pulpal nerve fibres is comparable to that of the cat, we hypothesize that the first pain component is evoked by intradental A delta fibres exhibiting their typical phasic response behaviour and firing during the initial steep temperature decrease. After some seconds, intradental temperature reached values sufficient to evoke C-fibre activity associated with the second pain component.
-
This study characterized the excitatory (nociceptive) and desensitizing (antinociceptive) properties of the natural pungent substances, capsaicin (CAP) and resiniferatoxin (RTX) instilled in the bladder (intravesical, i.ves.) via an indwelling cannula in awake, freely moving rats. The incidence of 9 behaviors was scored for 10 min following i.ves. vehicle or RTX (1.0 nmol). Abdominal licking and head-turning occurred significantly more often in RTX-treated rats compared to vehicle controls, whereas head-grooming, locomotion, rearing and biting did not differ between the two groups. ⋯ This study demonstrates that repeated application of both CAP and RTX into the bladder produces behavioral effects indicative of local sensory afferent desensitization. I.ves. CAP and RTX appear to produce their excitatory and desensitizing effects via a common mechanism, which is dependent on cation channel activation.(ABSTRACT TRUNCATED AT 400 WORDS)
-
Comparative Study
Long-term intrathecal infusion of morphine and morphine/bupivacaine mixtures in the treatment of cancer pain: a retrospective analysis of 51 cases.
A retrospective analysis of 51 patients with cancer pain treated with a continuous i.t. morphine infusion through a tunnelled percutaneous catheter was undertaken. Because of insufficient pain relief with morphine only, 17 of these patients received a morphine/bupivacaine mixture. Pain relief subsequently improved significantly in 10 patients and a moderate improvement was present in 4 patients. ⋯ No serious complications, neurologic sequelae or meningitis occurred. It is concluded that long-term i.t. infusion of morphine through a tunnelled catheter can provide adequate pain relief in cancer patients with an acceptable risk-benefit ratio. The effects of long-term intrathecal co-administration of local anesthetics, especially bupivacaine, await further prospective evaluation.
-
A 2-part study in which memory for everyday pains was investigated is reported. The first part compared ratings of vivid, 'flashbulb' memories of pain and non-pain events. Memories of pain events were rated as having been more surprising, having induced more negative emotional change, and having provoked greater change in ongoing activity than their non-pain event counterparts. ⋯ It is concluded that memories of painful events are readily retrievable and that the memory for a pain event, the sensory and affective qualities of pain experience and somatosensory component of pain are separated in their encoding and/or retrieval. The possible mechanisms whereby pain memories are encoded and retrieved are discussed. The clinical implications of the data concerning how judgements of past pain are made and the possible role of memory in coping are also noted.