REM SLEEP-SUPPRESSING EFFECTS OF ATROPINE IN CATS VARY WITH ENVIRONMENTAL-TEMPERATURE

Because the occurrence of rapid eye movement (REM) sleep is critically dependent upon an animal's thermal balance, acute pharmacological tre atments may effect REM sleep through effects on thermoregulation. We d escribe how manipulating ambient temperature (T-a) alters the REM slee p-suppressing effects of systemically-administered atropine, a muscari nic receptor antagonist, in adult cats. At a T-a of 23 degrees C, atro pine (0.5 mg/kg) produced a significant reduction in REM sleep time th at persisted for about 8 h of a 16 h recording period. Hypothalamic te mperature fell below control levels for about 4 h following atropine. At a T-a of 30 degrees C, the same dose of atropine had no significant effect on REM sleep time, or hypothalamic temperature. These findings indicate the importance of considering the possible role of thermoreg ulation in drug-induced effects on REM sleep.