Actions of a dopamine analogue and a neuroleptic at a neuroglandular synapse

Abstract

SUBSTANCES which mimic or inhibit the actions of dopamine in the vertebrate central nervous system (CNS) have become of increasing interest since the discovery of their potential clinical importance¹. It has been suggested that the receptors involved are closely associated with an adenylate cyclase responsible for the formation of cyclic AMP by homogenates of the neostriatum and limbic regions of the brain in the presence of dopamine². In favour of this idea, substances believed to be agonists for central dopamine receptors also stimulate the production of cyclic AMP in such homogenates^2,3, and neuroleptics, which are believed to act by blocking dopaminergic transmission, inhibit the action of dopamine on homogenates^2,4. It is difficult, however, to obtain information about the physiological mode of action of these compounds at the cellular level in the CNS. We report here the effects of a dopamine-like agonist and a neuroleptic on an alternative system which enables investigation of intracellular responses. Our results are consistent with the idea that both substances act directly on postsynaptic dopamine receptors.