Homeostatic, Entrainment and Pacemaker Effects of Drugs That Regulate the Timing of Sleep and Wakefulness,
HARVARD MEDICAL SCHOOL BOSTON MA DEPT OF PHYSIOLOGY AND BIOPHYSICS
Pagination or Media Count:
The timing of wakefulness and sleep in humans, and other diurnal primates such as the squirrel monkey Saimiri sciureus, is influenced not only by the duration of prior wakefulness or prior sleep, but also by the phase of the circadian timing system. In continuous, round-the-clock operations, or with transportation between time zones, conflicts frequently occur between these determinants of arousal state. The predictive circadian component favors wakefulness and sleep at phases consistent with the recent history of environmental and internal time cues. On the other hand, the reactive homeostatic component is principally determined by the length of prior wakefulness on the particular day in question. Investigations of pharmacological agents which influence the timing of sleep and wakefulness indicate they may exert their effects directly on the neuronalhumoral mechanisms responsible for the generation of sleep homeostatic effect, or by altering the phase of the circadian system. The circadian effects may either be achieved by resetting the phase of the circadian pacemaker pacemaker effects or may act by influencing the interaction between environmental light-dark cycles and circadian pacemakers entrainment effect. An appropriate strategy for the management of alert wakefulness at any hour of day and night must use the appropriate pharmacological tools to manage circadian and homeostatic components of wakefulness and sleep.