Alpha chloralose and nocturnal physiological patterns

Summary Sleep physiological patterns were examined following a single oral dose (500 mg) of the hypnotic drug alpha chloralose. The drug increased SW sleep and decreased REM sleep without affecting total sleep time or the amount of stage 2. These changes were accompanied by a shift to slower frequencies and greater EEG synchrony, as well as a decrease in the number of spontaneous arousals in all stages of sleep, and throughout the night of medication. Except for a slight decrease in eye movement density, the drug had no systematic effects on phasic phenomena such as electrodermal or cardio-respiratory fluctuations, nor was there a systematic change in basal heart and breathing rates.On the night following medication a rebound increase in percent stage REM was associated with a sharp decrease in SW sleep, and increases in spontaneous arousals and waking time. Such findings suggest that sleep stages are controlled by homeostatic mechanisms whose function is to maintain equilibrium.A comparison of the effects of alpha chloralose with those of the barbiturate secobarbital revealed some striking differences. Although both alpha chloralose and the barbiturate reduced the amount of stage REM and the frequency of brief arousals, the latter compound enhanced EEG fast activity and desynchrony, and suppressed such phasic phenomena as rapid eye movements during stage REM, sigma spindles in stage 2, nonspecific electrodermal responses during SW sleep and cardio-respiratory variability in all sleep stages. For secobarbital, the decrease in percent stage REM was compensated by an increase in stage 2 rather than SW sleep.Several studies in the cat suggest that in subanesthetic doses, alpha chloralose acts primarily on cortical inhibitory processes, causing release of the reticular activating system from inhibitory influences. The results of this study show that moderate doses in man probably act on both cortical and subcortical systems involved in the mediation of SW sleep, REM sleep and arousal.This study was supported in part by USPHS grant No. MH 10844-04 of the National Institute of Mental Health.We thank Lawrence C. Cowden and Orvis H. Rundell for their technical assistance and management of subjects, and Rosa Coulter and Cindy Williams for their contributions to analysis of data.