Effects of benzodiazepines on PGO firings and multiple unit activity in the midbrain reticular formation in cats.

Effects of benzodiapines administered by the intraperitoneal route on PGO firings and multiple unit activity in the midbrain reticular formation in chronic cat preparations were investigated at various levels of consciousness. Changes in the sleep-wakefulness cycle induced by direct injection of benzodiazepines into the reticular formation were also investigated. Benzodiazepines markedly decreased multiple unit activity in the midbrain reticular formation during each stage of sleep, but had little effect during behavioral and EEG arousal. Benzodiazepines did not affect PGO firing rate, but attenuated all increase of multiple unit activity following PGO firings. The bilateral injection of benzodiazepines into the midbrain reticular formation induced an increase of arousal and a decrease of slow wave sleep, but did not change the amount of paradoxical sleep. It is concluded that benzodiazepines show a mixture of depressant and facilitatory effects, which seem to vary with the state of consciousness of the animal.