Sleep-wakefulness rhythms in the rabbit.

The characteristics and stability of sleep-wakefulness patterns across consecutive 24-h periods were examined in adult male rabbits implanted for chronic recording of electroencephalographic, eye movement, and nuchal muscle activities. Criteria for stage scoring along with associated scoring reliability are presented. Rabbits slept an average of 11.4 h per day, 25.9% of which was drowsy, 64.5% slow wave sleep, and 9.6% paradoxical sleep. Diurnal differences in amount and type of sleep, consisting of increased wakefulness and decreased paradoxical sleep during the dark phase of the light-dark cycle, were observed. The results are integrated with those of previous sleep studies in this species and phylogenetic implications of variations in the distribution and characteristics of sleep in the rabbit are discussed.