The journal of pain : official journal of the American Pain Society
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In the present study, a murine ex vivo somatosensory system preparation was used to determine the response characteristics of cutaneous sensory neurons staining positively for TRPV1 or TRPV2. TRPV1 immunostaining was found exclusively (11/11) in a specific set of mechanically insensitive unmyelinated (C) nociceptors that responded to heating of their receptive fields. No cutaneous C-fibers that responded to both mechanical and heat stimuli stained positively for TRPV1 (0/62). The relationship between TRPV2 and heat transduction characteristics was not as clear, as few unmyelinated or myelinated fibers that responded to heat contained TRPV2. TRPV2 was found most frequently in mechanically sensitive myelinated fibers, including both low threshold and high threshold mechanoreceptors (nociceptors). Although TRPV2 was found in only 1 of 6 myelinated polymodal nociceptors, it was found in a majority (10/16) of myelinated mechanical nociceptors. Thus, whereas the in vivo role of TRPV1 as a heat-sensitive channel in cutaneous sensory neurons is clearly defined, the role of TRPV2 in cutaneous neurons remains unknown. These results also suggest that TRPV1 may be essential for heat transduction in a specific subset of mechanically insensitive cutaneous nociceptors and that this subset may constitute a discrete heat input pathway for inflammation-induced thermal pain. ⋯ The distinct subset of murine cutaneous nociceptors containing TRPV1 has many attributes in common with mechanically insensitive C-fibers in humans that are believed to play a role in pathological pain states. Therefore, these murine fibers provide a clinically relevant animal model for further study of this group of cutaneous nociceptors.
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Bee venom (BV) acupuncture (BVA) involves injecting diluted BV into acupoints and is used for arthritis, pain, and rheumatoid diseases. The objective of this systematic review was to evaluate the evidence for the effectiveness of BVA in the treatment of musculoskeletal pain. Seventeen electronic databases were systematically searched up to September 2007 with no language restrictions. All randomized clinical trials (RCTs) of BVA for patients with musculoskeletal pain were considered for inclusion if they included placebo controls or were controlled against a comparator intervention. Methodology quality was assessed and, where possible, statistical pooling of data was performed. A total of 626 possibly relevant articles were identified, of which 11 RCTs met our inclusion criteria. Four RCTs that tested the effects of BVA plus classic acupuncture compared with saline injection plus classic acupuncture were included in the main meta-analysis. Pain was significantly lower with BVA plus classic acupuncture than with saline injection plus classic acupuncture (weighted mean difference: 100-mm visual analog scale, 14.0 mm, 95% CI = 9.5-18.6, P < .001, n = 112; heterogeneity: tau(2) = 0, chi(2) = 1.92, P = .59, I(2) = 0%). Our results provide suggestive evidence for the effectiveness of BVA in treating musculoskeletal pain. However, the total number of RCTs included in the analysis and the total sample size were too small to draw definitive conclusions. Future RCTs should assess larger patient samples for longer treatment periods and include appropriate controls. ⋯ Bee venom acupuncture involves injecting diluted BV into acupoints and is used for arthritis, pain, and rheumatoid diseases. A meta-analysis produced suggestive evidence for the effectiveness of BVA in musculoskeletal pain management. However, primary data were scarce. Future RCTs should assess larger patient samples for longer treatment periods and include appropriate controls.
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The original Screener and Opioid Assessment for Patients with Pain (SOAPP) is a conceptually derived self-report questionnaire designed to predict aberrant medication-related behaviors among chronic pain patients considered for long-term opioid therapy. The purpose of this study was to develop and validate an empirically derived version of the SOAPP (SOAPP-R) that addresses some limitations of the original SOAPP. In successive steps, items were reduced from an initial pool of 142 to a 97-item beta version. The beta version was administered to 283 chronic pain patients receiving long-term opioid therapy. Items were evaluated based on data collected at follow-up, including correlation with the Aberrant Drug Behavior Index (ADBI), derived from interview data, physician ratings, and urine toxicology screens. Twenty-four items were retained and comprise the final SOAPP-R. Coefficient alpha was .88, and receiver operating characteristics curve analysis yielded an area under the curve of .81 (P < .001). A cutoff score of 18 showed adequate sensitivity (.81) and specificity (.68). The obtained psychometrics, along with the use of a predictive criterion that goes beyond self-report, suggest that the SOAPP-R is an improvement over the original version in screening risk potential for aberrant medication-related behavior among persons with chronic pain. ⋯ There is a need for a screener for abuse risk in patients prescribed opioids for pain. This study presents a revised version of the SOAPP-R that is empirically derived with good reliability and validity but is less susceptible to overt deception than the original SOAPP version 1.
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The agonist-antagonist kappa-opioid nalbuphine administered for postoperative pain produces greater analgesia in females than in males. In fact, males administered nalbuphine (5 mg) experience pain greater than those receiving placebo, suggesting the existence of an anti-analgesic effect. These sexually dimorphic effects on postoperative pain can be eliminated by coadministration of a fixed ratio of the prototypical opioid receptor antagonist naloxone with nalbuphine, implying a role for opioid receptors in the anti-analgesic as well as analgesic effects of nalbuphine. In the present study, we further evaluated the role of opioid receptors in the sex-specific effects on pain produced by nalbuphine by coadministering a dose of morphine low enough that it does not produce analgesia. After extraction of bony impacted third molar teeth, nalbuphine (5 mg) was administered alone or in combination with either of 2 low doses of morphine (2 mg or 4 mg). Both doses of morphine reversed nalbuphine-induced anti-analgesia in males, but only the lower dose (2 mg) reached statistical significance. Neither dose affected nalbuphine-induced analgesia in females, and when administered alone in either males or females, morphine (2 mg) had no analgesic effect. Though not observed in females, the effect of morphine in males argues that, like naloxone, low-dose morphine may act as an anti-analgesia opioid receptor antagonist. ⋯ Previously, we reported that the nalbuphine produces both analgesic and anti-analgesic effects and that the opioid antagonist naloxone can enhance nalbuphine analgesia by selectively antagonizing the anti-analgesic effect. Here we show that morphine, given in a subanalgesic dose, reverses nalbuphine-induced anti-analgesia in males, perhaps by a similar mechanism.