Role of the endocannabinoid system on the antihyperalgesic action of gabapentin in animal model of neuropathic pain induced by partial sciatic nerve ligation.

Gabapentin has antihyperalgesic action, decreasing central sensitization in neuropathic pain models; this effect depends on the mobilization of endogenous pain control pathways. This study aims to investigate the contribution of the endocannabinoid system to the antihyperalgesic action of gabapentin. Mus musculus Swiss, male, were submitted to PSL. On the 7th and 14th days post PSL, different groups were treated with CB1 receptor antagonist, AM281 via i.t. (2 μg/5 μl) or i.pl. (10 μg/20 μl) or CB2, AM630 via i.t. (5 μL i.t.) or (20 μL i.p.) and 15 min after gabapentin (30 mg / kg orally). Mechanical hyperalgesia was measured by the frequency of paw removal by the von Frey monofilament. Gabapentin demonstrated antihypernociceptive action, which was attenuated in animals pretreated with AM281 in both the i.t. and i.pl routes on the 7th and 14th days, differently from animals pretreated with AM630 that did not achieve a significant reduction with administration i.t. only on the 14th day with administration i.pl. The results show that endocannabinoid system contributes to the antihyperalgesic action of gabapetin in neuropathic pain by PSL, suggesting participation in the medullary and peripheral levels of CB1 receptors, and the peripheral performance of CB2 receptors.