Articles: hyperalgesia.
-
Randomized Controlled Trial Clinical Trial
Analgesic and antihyperalgesic effects of nabilone on experimental heat pain.
In this study, we explored the analgesic and antihyperalgesic properties of a synthetic cannabinoid (nabilone) on experimental heat pain in men and women, as well as its effects on descending pain inhibitory systems. ⋯ Nabilone failed to produce analgesic effects and it did not interact with descending pain inhibitory systems. However, we found that a single 1 mg dose of nabilone reduced temporal summation for women but not men. Although a titration regime and a larger sample of subjects might have provided more robust effects, these preliminary results suggest that nabilone appears effective at relieving hyperalgesic responses in women. Possible neurobiological mechanisms and clinical implications are further discussed.
-
Anesthesia and analgesia · Apr 2008
Midazolam administration reverses thermal hyperalgesia and prevents gamma-aminobutyric acid transporter loss in a rodent model of neuropathic pain.
Loss of gamma-aminobutyric acid (GABA) inhibition in the spinal dorsal horn may contribute to neuropathic pain. Here we examined whether systemic administration of the benzodiazepine midazolam would alleviate thermal hyperalgesia due to chronic constriction injury (CCI) of the sciatic nerve. ⋯ GABA inhibition plays an important role in neuropathic pain. Continuous systemic benzodiazepine administration may prove effective in alleviating neuropathic pain.
-
Clinical and experimental evidence suggests that glucocorticoids may be effective in the treatment of neuropathic pain, but their mechanism of action is unknown. We gave triamcinolone (3 mg/kg) to rats with an experimental post-traumatic painful peripheral neuropathy, chronic constriction injury (CCI), five days after nerve injury, when the abnormal pain syndrome is known to be present; and pain sensitivity was measured on postoperative days 7 - 14, a period during which symptoms are known to be at approximately peak severity. Additional CCI rats were treated similarly; and then they were sacrificed five days after the injection for an immunocytochemical analysis of endoneurial tumor necrosis factor-alpha (TNFalpha), macrophages, and mast cells in the sciatic nerve proximal to the site of injury. ⋯ On the nerve-injured side of vehicle-injected rats, TNFalpha was present in Schwann cells and mast cells. On the nerve-injured side of triamcinolone-treated rats, there was a significant (71.5%) reduction in the number of TNFalpha-positive mast cells. Our results suggest that glucocorticoid therapy for neuropathic pain may work via the reduced expression of TNFalpha in endoneurial mast cells.
-
Comparative Study
Exacerbated mechanical allodynia in rats with depression-like behavior.
Although a clinical connection between pain and depression has long been recognized, how these two conditions interact remains unclear. Here we report that both mechanical allodynia and depression-like behavior were significantly exacerbated after peripheral nerve injury in Wistar-Kyoto (WKY) rats, a genetic variation of Wistar rats with demonstrable depression-like behavior. ⋯ Moreover, there was a lower plasma melatonin concentration and a lower melatonin receptor expression in the anterior cingular cortex in WKY rats than in Wistar rats. These results suggest that there exists a reciprocal relationship between mechanical allodynia and depression-like behavior and the melatoninergic system in the anterior cingular cortex might play an important role in the interaction between pain and depression.