Effects of nootropic drugs on the sleep-waking pattern of the rat.

The effect of nootropic drugs on sleep-walking pattern was investigated in adult male Wistar rats. Continuous polygraphic sleep recording was made 8 h per day between 8.00 a.m. and 4.00 p.m. Piracetam (100 mg/kg), meclofenoxate (100 mg/kg), pyritinol (100 mg/kg), or methylglucamine orotate (225 mg/kg) were injected intraperitoneally immediately before the onset of recording. The substance effects were compared to pre-drug and post-drug NaC1 control days. The paradoxical sleep (PS) latency was prolonged by pyritinol and methylglucamine orotate. The percentage of PS was decreased by pyritinol and methylglucamine orotate, but increased by piracetam. Pyritinol and methylglucamine orotate decreased the number of PS episodes, whereas piracetam increased the mean duration of PS episodes. Meclofenoxate had no significant effects except for an increase in the number of very long PS episodes (5 min or more). Slow wave sleep and walking were affected only in the case of pyritinol. But also pyritinol, similar to piracetam and methylglucamine orotate, seems to have selective actions on PS as shown by the PS/total sleep ratio.