[Decrease of paradoxical sleep in the rat under tricyclic antidepressant: the role of collateral inhibition (author's...

The present study investigated the mechanisms of the action of a tricyclic antidepressant, desmethylimipramine, upon paradoxical sleep in the rat in acute administration. Desmethylimipramine induces an increase in paradoxical sleep latency, as well as a decrease of its total duration; these two modifications are dose-dependent. Different mechanisms may be evoked: inhibition of catecholamine synthesis, inhibition of locus coeruleus by adrenergic collaterals, or an anticholinergic effect. The results show that inhibition of synthesis is not quantitatively sufficient to induce the observed effects. It appears more probable that this decrease in paradoxical sleep results from a collateral inhibition, with the possible participation of an anticholinergic effect. The contributions of these different factors are discussed.