Effect of repeated application of nootropic drugs on sleep in rats.

The effects of repeated application of nootropic drugs on the sleep-wake cycle were investigated in rats. Piracetam, meclofenoxate and pyritinol were injected intraperitoneally, 100 mg/kg per day, during a period of 10 days. The sleep-wake cycle was recorded each day between 8 a.m. and 4 p.m. Repeated administration of piracetam and meclofenoxate led to an increase of the paradoxical sleep, a decrease of waking, and a very small increase of slow-wave sleep. Pyritinol, on the other hand, decreased the amount of paradoxical sleep. The paradoxical sleep latency was reduced by piracetam and meclofenoxate and enhanced by pyritinol, respectively. These findings and also previous results show that nootropic drugs have different effects on sleep, especially on paradoxical sleep. The possible relationship between sleep effects and memory effects of nootropic drugs and the usefulness of sleep studies for screening of nootropics are discussed.