Pain
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Comparative Study
Validation of a screener and opioid assessment measure for patients with chronic pain.
There has been a need for a brief assessment tool for providers who treat chronic pain patients to determine potential risk of abuse when prescribed opioids for pain. The purpose of this study was to develop and begin the validation of a self-administered screening tool (Screener and Opioid Assessment for Patients with Pain, SOAPP) for chronic pain patients considered for long-term opioid therapy. A consensus of 26 pain and addiction experts was obtained on important characteristics of chronic pain patients that predict future medication misuse using concept mapping. ⋯ Coefficient alpha for these 14 items was acceptable for a short scale (0.74). Receiver operating characteristics curve analysis yielded an area under the curve of 0.881 (P<0.001), suggesting adequate sensitivity and specificity for a screening device. These reliability and predictive validity results suggest that the SOAPP is a promising step toward screening risk potential for substance misuse among persons with chronic pain.
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Comparative Study
Perception and modulation of pain in waking and hypnosis: functional significance of phase-ordered gamma oscillations.
Somatosensory event-related phase-ordered gamma oscillations (40-Hz) to electric painful standard stimuli under an odd-ball paradigm were analyzed in 13 high, 13 medium, and 12 low hypnotizable subjects during waking, hypnosis, and post-hypnosis conditions. During these conditions, subjects received a suggestion of Focused Analgesia to produce an obstructive hallucination of stimulus perception; a No-Analgesia treatment served as a control. After hypnosis, a post-hypnotic suggestion was given to draw waking subjects into a deep hypnosis with opened eyes. ⋯ Phase-ordered gamma scores over central scalp site predicted subject pain ratings across Waking-Pain and Waking-Analgesia conditions, while phase-ordered gamma scores over frontal scalp site predicted pain ratings during post-hypnosis analgesia condition. During waking conditions, this relationship was present in high, low and medium hypnotizable subjects and was independent of stimulus intensity measures. This relationship was unchanged by hypnosis induction in the low hypnotizable subjects, but not present in the high and medium ones during hypnosis, suggesting that hypnosis interferes with phase-ordered gamma and pain relationship.
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Comparative Study
Involvement of cholecystokinin in the opioid tolerance induced by dipyrone (metamizol) microinjections into the periaqueductal gray matter of rats.
The analgesic effect of non-steroidal anti-inflammatory drugs (NSAIDs) is partly due to an action upon the periaqueductal gray matter (PAG), which triggers the descending pain control system and thus inhibits nociceptive transmission. This action of NSAIDs engages endogenous opioids at the PAG, the nucleus raphe magnus and the spinal cord. Repeated administration of NSAIDs such as dipyrone (metamizol) and acetylsalicylate thus induces tolerance to these compounds and cross-tolerance to morphine. ⋯ In rats tolerant to PAG dipyrone, a PAG microinjection of proglumide restored the antinociceptive effect of a subsequent microinjection of dipyrone or morphine. These results suggest that PAG-microinjected dipyrone triggers and/or potentiates local opioidergic circuits leading to descending inhibition of nociception, on the one hand, and to a local antiopioid action by cholecystokinin, on the other. Reiteration of these events would then result in an enhancement of cholecystokinin's antiopioid action and thus tolerance to opioids and dipyrone in the PAG.
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Comparative Study
Intracerebroventricular injection of phospholipases A2 inhibitors modulates allodynia after facial carrageenan injection in mice.
The present study was carried out, using inhibitors to secretory phospholipase A2 (sPLA2, 12-epi-scalaradial), cytosolic phospholipase A2 (cPLA2, AACOCF3), or calcium-independent phospholipase A2 (iPLA2, bromoenol lactone), to compare possible contributions of central nervous PLA2 isoforms to the development of allodynia after facial carrageenan injection in mice. C57BL/6J (B6) mice showed increased responses to facial stimulation using a von Frey hair (1 g force), at 8 h, 1 day, and 3 days after facial carrageenan injection. On the other hand, BALB/c mice did not show increased responses at any of the time points. ⋯ Since BALB/c mice did not show increased responses after facial carrageenan injection, the reduction in responses actually indicates that there is loss of normal sensitivity to von Frey hair stimulation after intracerebroventricular injection of each of these inhibitors, in this strain of mice. The effects of PLA2 inhibitors are unlikely to be due simply to inhibition of arachidonic acid generation, since intracerebroventricular injection of arachidonic acid also had an anti-nociceptive effect. The above results support an important role of central nervous PLA2s in neurotransmission and pain transmission.
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Comparative Study
Spontaneous discharge and increased heat sensitivity of rat C-fiber nociceptors are present in vitro after plantar incision.
Postoperative pain is characterized by spontaneous pain at the surgical site and increased pain due to movements. To study postoperative pain mechanisms, we investigated discharge properties of mechano-heat sensitive C-fiber afferents innervating the rat glabrous hindpaw skin 1 day after plantar incision. Behaviors indicating spontaneous pain, heat and mechanical hyperalgesia were present 1 day after incision. ⋯ The mean mechanical response thresholds, measured by a servo force-controlled stimulator, were not different between groups. The total spikes evoked at supra-threshold mechanical stimulation were not increased in afferents from the incision. In conclusion, 1 day after incision, when behaviors indicating spontaneous pain, heat and mechanical hyperalgesia are present, C-fibers close to incision showed spontaneous discharge and sensitization to heat but not to mechanical stimuli, in vitro.