THE INTERMEDIATE STAGE AND PARADOXICAL SLEEP IN THE RAT - INFLUENCE OF 3 GENERATIONS OF HYPNOTICS

Paradoxical sleep in the rat, cat and mouse is preceded and sometimes followed by a short-lasting intermediate stage characterized by high-a mplitude anterior cortex spindles and low-frequency hippocampal theta rhythm. Several neurophysiological arguments suggest that the intermed iate stage corresponds to a brief functional disconnection of the fore brain from the brainstem. This paper is devoted to the review of quant itative and qualitative influences of three generations of hypnotics o n the intermediate stage-paradoxical sleep couple. Barbiturates, first -generation hypnotics, extend the intermediate stage at the expense of paradoxical sleep. Three benzodiazepines are compared, two with a sho rt half-life (triazolam and midazolam) and one with a long half-life ( diazepam). They also decrease sleep occurrence latency and increase th e intermediate stage at the expense of paradoxical sleep, except for m idazolam, which increases both the intermediate stage and paradoxical sleep at low dose. Zolpidem and zopiclone, hypnotics of third generati on, decrease paradoxical sleep but the intermediate stage never substi tutes for paradoxical sleep. The results are discussed in relationship to the functional aspects of this turning-point period of sleep.