Sleep and nitric oxide: effects of 7-nitro indazole, inhibitor of brain nitric oxide synthase.

We examined the effect of 7-nitro indazole (7-NI, 2.5-50 mg/kg, i.p.), an inhibitor of central nitric oxide (NO) synthesis, on general behaviour and sleep. The results show that 7-NI induces ptosis, a loss of the righting reflex and decrease of the EEG amplitudes. Furthermore, a duration of slow wave sleep (SWS) and REM sleep decreased, while the latencies of SWS and REM sleep increased. The effects of 7-NI on general behaviour and sleep were partially antagonized by intraventricular administration of the NO precursor, L-arginine (600 micrograms). These findings indicate that 7-NI induces a state of prominent central depression associated with motor deficit and decrease in sleep stages and wakefulness. It further suggests that NO exerts a significant excitatory effect on the neuronal structure involved in the regulation of locomotion and vigilance.