The effect of intraaccumbal injection of L-arginine and L-NAME on induction and removal of conditioned place preference in rat

Nucleus accumbens (Nac) has been considered as a center for the induction of drug dependence. Since a high concentration of the enzyme, nitric oxide synthase (NOS) has been found in the Nac, and this fact that the role of nitric oxide (NO) in acquisition and expression of drug dependence has become clear in recent years, therefore in this study the effects of intraaccumbal injections of L-arginine (NO precursor) and L-NAME (N-ω-nitro-L-arginine methyl ester) or aminobiguanidine (NOS inhibitor) on induction of conditioned place preference (CPP) in rat were investigated. For this purpose, male Wistar rats (250-300 g) were used. Five days after surgery and cannulation, different doses of L-arginine, L-NAME or aminobiguanidine were injected to animals and conditioning was performed. The results showed that: I) intraaccumbal injection of L-arginine at doses of 0.3, 1 and 3 µg/rat induced CPP. 2) Acute administration of L-NAME (50 mg/kg i.p.) reduces the effect of L-arginine and chronic administration of the drug (10, 50, and 200 mg/kg i.p.) has no effect. 3) intraaccumbal injection of both L-NAME and aminobiguanidine (0.3, 1, and 3 µg/rat) produces no effect. In conclusion, it seems likely that intraaccumbal injection of L-arginine could induce CPP and part of its effect might be due to the release of NO from L-arginine.