Involvement of pre- and postsynaptic receptors in catecholaminergic control of paradoxical sleep in man.

In an attempt to clarify the roles of pre- and postsynaptic catecholaminergic (CA) receptors in the regulation of paradoxical sleep (PS) in man, the effects of various doses of chlorpromazine (CPZ) and clonidine (CLN) have been investigated. The action of CPZ was biphasic, small doses enhancing and larger doses depressing the production of PS. However, the effect of CLN was monophasic, showing no modification after small doses, and a decrease in production of PS after moderate doses. In addition, a small dose of CLN, ineffective by itself, completely abolished the effect of a small dose of CPZ. These observations can be explained by preferential blockade of presynaptic alpha-receptors by a small dose of CPZ. They show, too, that it is possible to investigate in man the functional consequences of pharmacological manipulation of pre-synaptic receptors on cerebral CA neurons.