Neurotransmitter mechanisms in gabapentin antinociception

The present study was done to investigate the neurotransmitter mechanisms involved in gabapentin antinociception in healthy albino rats. The formalin test was used to asses antinociception. Gabapentin (10-120 mg/kg s.c.) decreased the pain score in the formalin test. In order to study the putative neurotransmitter mechanisms involved in gabapentin action, the effect of gabapentin (30 mg/kg s.c.) alone and in rats pretreated with different receptor blockers, e.g. bicuculine, saclofen, naloxone, mecamylamine, atropine, DL-p-chlorophenylalanine methyl ester hydrochloride, glibenclamide, theophylline, and L-arginine was assessed. Gabapentin decreased the pain score, and the ED(50) of gabapentin was 36.8 +/- 8.2 (30.2-43.1) mg/kg s.c. Pretreatment with different receptor blockers did not modify gabapentin (30 mg/kg s.c.) antinociception except for L-arginine which increased the pain score from 1.68 +/- 0.29 (gabapentin) to 2.29 +/- 0.41. Results suggest the involvement of L-arginine nitric oxide pathways in gabapentin antinociception.