Apomorphine stereotypies and transmitter mechanisms in the striatum. II. Interactions between GABA-ergic and cholinergic transmission.

The interactions between the GABA-ergic and cholinergic transmissions in the striatum of male mice are determined through microinjection in the striatum of agents influencing these types of transmission in cases of apomorphine stereotypies. It is found that the agents acting on the cholinergic transmission (agonists and antagonists of the muscarinic and nicotinic cholinoreceptors), antagonize considerably the reducing effect on apomorphine stereotypies of the agents acting on GABA-ergic transmission. Conversely, the agents acting on GABA-ergic transmission (pre- and post-synaptic) intensify or weaken the effects of the agents acting on the cholinergic transmission with respect to apomorphine stereotypies, though the difference is not entirely significant. The influence of the effects of the agents acting on the GABA-ergic transmission in cases of apomorphine stereotypies is thought to be due to the antagonistic action of the striatal cholinergic neurones on the GABA-ergic neurones, while the latter interact with the striatal dopaminergic neurones either directly or through the mediation of substantia nigra. The lack of direct interactions between the GABA-ergic and the cholinergic neurones in the striatum explains the weak influence on cholinergic transmission exerted by the agents acting on the GABA-ergic transmission with respect to apomorphine stereotypies.