Contrasting effects of two 5-hydroxytryptamine-depleting drugs on sleep patterns in cats

Slow-wave sleep increased in cats after administration of a 5-hydroxytryptamine (5-HT)-depleting dose of fenfluramine while it was decreased by p-chlorophenylalanine (pCPA), another 5-HT-depleting drug. Fenfluramine reversed the reduction in sleeping time resulting from pCPA administration and this reversal was blocked by AHR-3009, a 5-HT antagonist. These data suggest that although brain 5-HT levels may not be involved in the sedative action of fenfluramine, sleep was induced by an action on a tryptaminergic pathway.