Diazepam and midazolam increase light slow-wave sleep (SWS1) and decrease wakefulness in rats.

Rats implanted with electrodes for polygraphic recordings were injected with diazepam (5 mg/kg, i.p.) or midazolam (10 mg/kg, i.p.) and recorded for 6 h during the 8 h of darkness of a 16 h light/8 h dark cycle. The results show that administration of diazepam reduced SWS1 latency by 92%, and increased SWS1 and total sleep by 255% and 59%, respectively, in comparison to control. Administration of midazolam increased SWS1 by 158% and total sleep by 57% when compared to control. These findings correlate well with the effects of benzodiazepines on sleep stage 2 in humans and indicate that benzodiazepine hypnotics increase only the behaviorally lighter stage of SWS in rats as well as in human subjects.