Nitro-1-Arginine Attenuates SKF 38393 - Induced Oral Activity in Neonatal 6-Hydroxydopamine-Lesioned Rats

Nitric oxide (NO) in brain has been implicated in neuronal regulatory processes and in neuropathologies. Previously we showed that NO modified quinpirole-induced yawning, a behavioral measure of dopamine (DA) Da receptor activation in rats. The aim of this study was to characterize the effect of nitro-L-arginine methyl ester HC1 (NAME) and L-arginine HC1 on reactivity of rats to the DA DI receptor agonist SKF 38393 and DA DI antagonist SCH 23390 in intact and neonatal 6-hydroxydopamine (o-OHDA)-lesioned rats (134 ng of base ICV at 3rd day after birth). L-arginine HC1 (300 mg/kg IP) increased the oral activity response in 6-OHDA-lesioned rats, like SKF 38393, and induced catalepsy in intact control rats, like SCH 23390. In contrast, NAME had no effect on oral activity or catalepsy, but fully attenuated SKF 38393-induced oral activity. These findings indicate that L-arginine HC1 has no apparent effect at the DA DI receptor, but that NAME is effective in attenuating a DA DI agonist induced effect. Consequently NO may be an intracellular second messenger for supersensitized receptors associated with DA DI agonist - induced oral activity