INFLUENCE OF ZOPICLONE, A NEW-GENERATION HYPNOTIC, ON THE INTERMEDIATE STAGE AND PARADOXICAL SLEEP IN THE RAT

This study examined the influence of zopiclone, a third generation hyp notic, on the transition from slow wave sleep to paradoxical sleep (PS ) which is increased at the expense of PS by barbiturates and benzodia zepines. The compound decreased sleep latency and increased the latenc y of the intermediate stage (IS) and PS at 2.5, 5 and 7.5 mg/kg IP. Th e amount of the IS was decreased because of the decrease in phase numb er up to 6 h at all doses. PS amount was decreased during 2 h at 2.5 m g/kg and during 4 h at 5 and 7.5 mg/kg also because of the decrease in phase number. The IS never substituted for PS. The IS spindle charact eristics were not modified and the theta rhythm frequency slightly dec reased at 5 mg/kg (IS) and 7.5 mg/kg (PS).