Effects of the GABAB antagonist CGP 35348 on sleep-wake states, behaviour, and spike-wave discharges in old rats.

The GABAB antagonist CGP 35348 was intraperitoneally given in doses of 100, 300, and 900 mg/kg to old rats. These rats were earlier chronically provided with EEG and EMG electrodes. Sleep recordings based on visual inspection of EEG and EMG recordings were made for 3 h post injection, and spontaneous behaviour in the recording cage was additionally observed. With 100 and 300 mg/kg, the drug produced an increase in the duration of REM sleep compared to the saline-injected control group. The REM sleep latency was correspondingly reduced. Non-REM sleep and total sleep duration increased and an s-shaped dose-response relationship was found. Explorative behaviour was diminished after injections with 100 and 300 mg/kg CGP 35348. The number and duration of spike-wave discharges were reduced after all doses of CGP 35348 and during all 3 recording hours. The latter outcomes confirm the strong suppressive action of this drug on spike-wave discharges; these effects have also been reported in models of absence epilepsy. The hypnotic properties and especially the increase in REM sleep after the administration of CGP 35348 deserve attention considering the paucity of drugs which facilitate REM sleep. The discovery of drugs promoting REM sleep might have theoretical as well as clinical consequences.