Pain
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We evaluated the role of sigma(1) receptors on capsaicin-induced mechanical hypersensitivity and on nociceptive pain induced by punctate mechanical stimuli, using wild-type and sigma(1) receptor knockout (sigma(1)-KO) mice and selective sigma(1) receptor-acting drugs. Mutation in sigma(1)-KO mice was confirmed by PCR analysis of genomic DNA and, at the protein level, by [(3)H](+)-pentazocine binding assays. Both wild-type and sigma(1)-KO mice not treated with capsaicin showed similar responses to different intensities of mechanical stimuli (0.05-8 g force), ranging from innocuous to noxious, applied to the hind paw. ⋯ The effects of the sigma(1) antagonists were reversed by the sigma(1) agonist PRE-084 (32 mg/kg, s.c.). None of the drugs tested modified the responses induced by a painful mechanical punctate stimulus (4 g force) in nonsensitized animals. These results suggest that sigma(1) receptors are essential for capsaicin-induced mechanical hypersensitivity, but are not involved in mechanical nociceptive pain.
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Comparative Study
Deficiency in endogenous modulation of prolonged heat pain in patients with Irritable Bowel Syndrome and Temporomandibular Disorder.
Females with Irritable Bowel Syndrome (IBS) and Temporomandibular Disorder (TMD) are characterized by enhanced sensitivity to experimental pain. One possible explanation for this observation is deficiencies in pain modulation systems such as Diffuse Noxious Inhibitory Control (DNIC). In a few studies that used brief stimuli, chronic pain patients demonstrate reduced DNIC. ⋯ Compared to controls, IBS and TMD patients reported an increased sensitivity to heat pain and failed to demonstrate pain inhibition due to DNIC. Controls showed a significant reduction in pain during the DNIC session. These findings support the idea that chronic pain patients are not only more pain sensitive but also demonstrate reduced pain inhibition by pain, possibly because of dysfunction of endogenous pain inhibition systems.
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Controlled Clinical Trial
Moderation and mediation in the psychological and drug treatment of chronic tension-type headache: the role of disorder severity and psychiatric comorbidity.
We evaluated two putative moderators of treatment outcome as well as the role of Headache Management Self-Efficacy (HMSE) in mediating treatment outcomes in the drug and non-drug treatment of chronic tension-type headache (CTTH). Subjects were 169 participants (M=38 yrs.; 77% female; M headache days/mo.=22) who received one of four treatments in the treatment of CTTH trial (JAMA, 2001; 285: 2208-15): tricyclic antidepressant medication, placebo, (cognitive-behavioral) stress-management therapy plus placebo, and stress-management therapy plus antidepressant medication. Severity of CTTH disorder and the presence of a psychiatric (mood or anxiety) disorder were found to moderate outcomes obtained with the three active treatments and with placebo, as well as to moderate the role of HMSE in mediating improvements. ⋯ HMSE mediated treatment outcomes in the two stress-management conditions, but the pattern of HMSE mediation was complex, varying with the treatment condition, the outcome measure, and the moderator variable. Irrespective of the severity of the CTTH disorder HMSE fully mediated observed improvements in headache activity in the two stress-management conditions. However, for patients with a mood or anxiety disorder HMSE only partially mediated improvements in headache disability, suggesting an additional therapeutic mechanism is required to explain observed improvements in headache disability in the two stress-management conditions.
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Despite wide usage of the Numerical Rating Scale (NRS) for self-report of pain intensity in clinical practice with children and adolescents, validation data are lacking. We present here three datasets from studies in which the NRS was used together with another self-report scale. Study A compared post-operative pain ratings on the NRS with scores on the Faces Pain Scale-Revised (FPS-R) in 69 children age 7-17 years who had undergone a variety of surgical procedures. ⋯ In Study C, the distributions of scores on the NRS and VAS were very similar except that scores closest to the no pain anchor were more likely to be selected on the VAS than the NRS. The NRS can be considered functionally equivalent to the VAS and FPS-R except for very mild pain (<1/10). We conclude that use of the NRS is tentatively supported for clinical practice with children of 8years and older, and we recommend further research on the lower age limit and on standardized age-appropriate anchors and instructions for this scale.