Effects on sleep of phentolamine and epinephrine infused into the locus coeruleus of cats.

The sleep-wavefulness behavior of cats was studied after infusion of phentolamine (3 micrograms, bilateral) or epinephrine (60 micrograms, bilateral) into the locus coeruleus. The drugs exerted opposite effects: phentolamine increased rapid eye movement (REM) sleep and decreased light slow wave sleep; epinephrine decreased REM sleep, increased light slow wave sleep and augmented wakefulness. The REM-enhancing effect of phentolamine was due to more REM periods than in control experiments, with a shortening of the sleep cycle. Epinephrine, by contrast, resulted in fewer REM periods and a prolongation of the sleep cycle. The data support the hypothesis that pontine catecholamines inhibit REM sleep and facilitate wakefulness in cats, and implicate the rostral pons as an important site for the REM-increasing effect of systemically administered phentolamine.