Paradoxical sleep and brain catecholamines in the rat after single and repeated administration of alpha-methyl-paratyrosine

Abstract

This study is concerned with the role of catecholamines (CA) in the regulation of paradoxical sleep (PS) in the rat. Alpha-methyl-paratyrosine (alphaMPT), an inhibitor of tyrosine hydroxylase, was used in a multiple administration schedule in order to avoid toxic effects. From 2 to 10 doses of 75 mg/kg of alphaMPT, a progressive reduction of green fluorescence occurred in CA cell bodies as well as in terminals. The green fluorescence reduction was faster in dopaminergic than in noradrenergic neurons, and faster in cell bodies than in terminals. Sleep recordings showed a slight increase of PS after one or two doses of 75 mg/kg of alphaMPT, and a dose-related decrease after 3-7 injections. After two doses of 75 mg/kg, the number of PS phases was significantly increased. This can be due to the release of a non-CA PS primer mechanism. These experiments support the view that an intact synaptic transmission in CA neurons is necessary for the realization of PS.