Cyclic nucleotide levels in the rat striatum and cerebellum—: In vivo effects of dopamine and acetyl-choline receptor agonists and antagonists

Abstract The role of dopamine and acetylcholine receptors in the regulation of cyclic nucleotide levels in the striatum and cerebellum was investigated after in vivo administration of drugs. Apomorphine increased cyclic AMP levels only in the striatum and this effect was blocked by haloperidol and dexetimide. Cyclic GMP levels were increased both in the striatum and cerebellum by apomorphine and pilocarbine. Haloperidol significantly decreased cyclic GMP levels and blocked the effect of apomorphine and pilocarpine on cyclic GMP in the cerebellum. In the striatum, haloperidol blocked only the pilocarpine-induced rise of cyclic GMP. Dexetimide increased cyclic GMP levels and failed to block the rise in cyclic GMP by either apomorphine or pilocarpine. These results suggest that the regulation of cyclic GMP levels may involve more than one mechanism.