Effects of methysergide in cats deprived of paradoxical sleep.

Methysergide maleate, a 5-hydroxytryptamine receptor blocker, was administered to cats deprived of paradoxical sleep for 48 hours. During the first six hours after methysergide, the latency to the first slow-wave sleep and paradoxical sleep episodes was increased and total sleep time decreased. The decrease in sleep reflects a loss of paradoxical sleep, while the amount of slow-wave sleep remained unchanged. Slow-wave sleep time, though unchanged in amount, was displaced to the end of the six-hour recording period. These results suggest that paradoxical sleep in cats is more sensitive to methysergide action than is slow-wave sleep.