Pharmacological Research Communications, Vol. 8, No. 2, 1976 143 ON THE CYCLIC NUCLEOTIDES INVOLVEMENT IN RAT STRIATAL FUNCTION A. Carenzi, S. Govoni, P.F. Spano and M. Trabucchi Department of Pharmacology and Pharmacognosy,University of Milan Received 9 January 1976 SUMMARY Recently it has been reported that an increase of striatal dopamine (DA) receptor stimulation leads to an enhancement of striatal cyclic adenosine 3',5'-monophosphate (CAMP). Moreover the stimulation of muscarinic receptors in the central nervous system (C.N.S.) has been correlated with the increase of cyclic guanosine 3',5'-monophosphate (cGMP). Since DA in striatum functions as inhibitory transmitter on cholinergic neurons we investigated the effect of an increased stimulation of DA recep- tors produced by (+) amphetamine and apomorphine on the cGMP content in stri atum. On the other hand we studied the CAMP and cGMP levels after chemical- degeneration of substantia nigra, when the function of DA receptors is im- paired. The increase of striatal CAMP and cGMP levels after (+) amphetamine and apomorphine and the increase of cGMP contents after the lesion of the nigro-striatal patways have been discussed. INTRODUCTION Many reports indicate that the response of neurons in the CNS to neuro- transmitters may be mediated by intracellular changes of CAMP or cGMP con- tents. An increase of striatal DA receptor stimulation produced by (+) am- phetamine (Costa et a1.,1973) or apomorphine (Carenzi et a1.,1975) leads to a selective increase of CAMP levels in striatum. On the other hand, the activity of muscarinic receptors in the CNS (Fer- randelli et a1.,1972) or the release ofy-aminobutyric acid in cerebellum (Mao et a1.,1974) have been correlated with cGMP content variations. Extensive evidence indicates the existence in striatum of a functional link between dopaminergic and cholinergic system. Trabucchi et a1.(1975) demonstrated that the increase of dopaminergic activity produced by (+) am- phetamine or apomorphine inhibits acetylcholine turnover in striatum.