Multiunits in the mesencephalic reticular formation: ontogenetic development of wakefulness and sleep cycle in the rat.

Recording of multiunit activity (MUA) from the mesencephalic reticular formation (MRF) of freely behaving rats, aged between 1 and 120 days, revealed that state dependent changes in cell firing associated with wakefulness and sleep cycle were present from the first day of life. The MRF neuron populations were found to gain the adult-like functional properties by the 9-11th postnatal day. The paradoxical sleep phases attained adult characteristics by day 12-13 and the average duration of slow wave sleep episodes was that of adult rats at the end of the 4th week, the maturation of sleep behavior was completed at the age of day 33-35.