5-Hydroxytryptamine neurons and the sleep-wakefulness cycle. Effects of methergoline and zimelidine.

Methergoline, a 5-hydroxytryptamine (5-HT) receptor blocking agent, produced a significant decrease in the number of slow wave sleep 2 (SWS 2) and paradoxical sleep (PS) episodes and an increase in the length of wakefulness (W) episodes. Zimelidine, a specific 5-HT uptake blocking agent, produced a significant reduction of the number of PS episodes and an increase in the number of spisodes spent in W and slow wave sleep 1 (SWS 1), the total time spent in SWS 1 being increased. The findings demonstrate that increases and decreases of 5-HT receptor activity will produce differential effects on SWS 2 events and on W mechanisms.