MONOAMINERGIC AND CHOLINERGIC MODULATION OF REM-SLEEP TIMING IN RATS

The effects on sleep structure of systemic administration of benchmark cholinergic, serotonergic, and noradrenergic antagonists (QNB, ritans erin, metergoline, and prazosin) were characterized in rats using a ne w technique for identifying transitions (NRTs) from non-REM (NREM) sle ep to REM sleep. In agreement with previous studies, all agents tested reduced REM-sleep expression (by 36-86%). In addition, the serotonerg ic and noradrenergic antagonists reduced NRT frequency (by 58-81%). Th e cholinergic antagonist QNB had no effect on NRT frequency. These fin dings suggest that blockade of serotonergic or noradrenergic receptors increases the interval between REM-sleep episodes, perhaps reducing t he rate of accumulation of REM-sleep propensity. Blockade of cholinerg ic receptors, by contrast, decreases REM-sleep-expression by interferi ng with REM-sleep maintenance, not by modulating REM-sleep timing. The se conclusions are contrary to the predictions of a number of publishe d models of REM-sleep timing.