Pain
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Comparative Study
Rapid deterioration of pain sensory-discriminative information in short-term memory.
The assessment of pain and analgesic efficacy sometimes relies on the retrospective evaluation of pain felt in the immediate, recent or distant past, yet we have a very limited understanding of the processes involved in the encoding, maintenance and intentional retrieval of pain. We examine the properties of the short-term memory of thermal and pain sensation intensity with a delayed-discrimination task using pairs of heat pain, warm and cool stimulation in healthy volunteers. Performance decreased as a function of the inter-stimulus interval (ISI), indicating a robust deterioration of sensory information over the test period of 4-14 s. ⋯ Importantly, performance declined steadily with increasing ISI (from 6 to 14 s)--but only for pairs of heat pain stimuli that were relatively difficult to discriminate (Delta-T < or = 1.0 degree C; perceptual difference < or = 32/100 pain rating units) while no deterioration in performance was observed for the largest temperature difference tested (Delta T = 1.5 degrees C; perceptual difference of 50 units). These results are consistent with the possibility that short-term memory for pain and temperature sensation intensity relies on a transient analog representation that is quickly degraded and transformed into a more resistant but less precise categorical format. This implies that retrospective pain ratings obtained even after very short delays may be rather inaccurate but relatively reliable.
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Comparative Study
HIV-1 gp120 stimulates proinflammatory cytokine-mediated pain facilitation via activation of nitric oxide synthase-I (nNOS).
It has become clear that spinal cord glia (microglia and astrocytes) importantly contribute to the creation of exaggerated pain responses. One model used to study this is peri-spinal (intrathecal, i.t.) administration of gp120, an envelope protein of HIV-1 known to activate glia. Previous studies demonstrated that i.t. gp120 produces pain facilitation via the release of glial proinflammatory cytokines. ⋯ Both abolished gp120-induced mechanical allodynia. While the literature pre-dominantly documents that proinflammatory cytokines stimulate the production of NO rather than the reverse, here we show that gp120-induced NO increases proinflammatory cytokine mRNA levels (RT-PCR) and both protein expression and protein release (serial ELISA). Furthermore, gp120 increases mRNA for IL1 converting enzyme and matrix metalloproteinase-9, enzymes responsible for activation and release of proinflammatory cytokines.
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Comparative Study
Maintenance of windup of second pain requires less frequent stimulation in fibromyalgia patients compared to normal controls.
Many chronic pain syndromes, including fibromyalgia (FM), show evidence of central nervous system hyperexcitability related to central sensitization. Windup (WU) of second pain reflects increased excitability of spinal cord neurons that is related to central sensitization. Psychophysical testing can help characterize this important central nervous system phenomenon because of the parallels between electrophysiological WU and WU of second pain. ⋯ Thus, unlike NC subjects, FM subjects showed enhanced second pain during WU-M stimuli at very low stimulus frequencies, indicating central sensitization. Increased WU sensitivity, enhanced WU-M, and increased WU-related aftersensations help account for persistent pain conditions in FM subjects. In addition to WU, WU-M appears to be a useful tool to study mechanisms of pain in patients with characteristics of central sensitization.
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Pain catastrophizing and interpersonal problems: a circumplex analysis of the communal coping model.
Using the circumplex model of interpersonal behavior [Handbook of research methods in clinical psychology, 1982], this study tested the communal coping model of catastrophizing (CCM) in a large (N = 179) sample of patients with irritable bowel syndrome (IBS), a common, benign chronic pain disorder associated with significant painful extraintestinal comorbidity (e.g. headache, low back pain). Patients completed the Coping Strategies Questionnaire, the Brief Symptom Inventory, and the Inventory of Interpersonal Problems. ⋯ In general, data provide evidence supporting the interpersonal distinctiveness of pain catastrophizing as postulated by the CCM. Advantages of a circumplex model and of interpersonal theory for understanding and testing the CCM are discussed.