Postnatal development of spontaneous neuronal discharges in the pontine reticular formation of free-moving rats during sleep and wakefulness.

A developmental study has been made of spontaneous neuronal activity within the pontine reticular formation (giant cell field: FTG) of the rat between one week and one month after birth. Through day 14, the recorded FTG neurons discharged more frequently during quite sleep (QS) than was generally true in older animals. In addition, they were active to the same extent during active-sleep (AS) as during waking-with-movements (AW). In contrast, most of the cells recorded from day 15 on were considerably more active during AS and AW, relative to the QS level, than had hitherto been the case. This new class of neurons, in turn, fell into two sub-groups, one of which was most active during AW while the other was more active during AS. Clomipramine selectively suppressed AS along with the neuronal activity patterns associated with it, and in many cases the QS firing level was even lower than it had been prior to the injection. It is concluded that FTG unit activity is an excellent monitor for controlling the effectiveness of experimental manipulations of AS but is probably not involved in its generation.