Antiallodynic Effect of Piperine in Neuropathic Rats

Neuropathic pain is a disabling syndrome difficult to manage. Currently, pharmacological treatment of neuropathic patients provides an unsatisfactory relief of pain. Recent reports suggested that piperine has anti-inflammatory and antinociceptive effects. Therefore, the aim of this study was to investigate the antiallodynic effect of piperine, as well as the possible antinociceptive mechanism involved in its antiallodynic effect. Piper nigrum L., Piperaceae, was used to extract the piperine. Spinal nerve ligation L5/L6 model was used to induce allodynia in rats. Intraperitoneal administration of increasing doses of piperine (3.1–100 mg/kg) reduced allodynia in rats. The administration of capsazepine (selective TRPV1 antagonist, 5 and 30 μg/i.t.) and bicuculline (GABAA antagonist, 3 and 30 μg/i.t.), but not SKF-96365 (TRPC antagonist, 3 and 30 μg/i.t.), prevented the piperine-induced (56 mg/kg, i.p.) antiallodynic effect in a dose-dependent manner. HC-030031 (selective TRPA1 antagonist, 3 and 30 μg/i.t.) avoided only partially piperine-induced (56 mg/kg, i.p.) antiallodynic effect. Data suggest that piperine induces antiallodynic effect in neuropathic rats, and its antiallodynic effect involves the activation of TRPV1 and GABAA receptors. Piperine could be useful to treat neuropathic pain in human beings.