Effect of quinolinic acid on wakefulness and sleep in the rabbit.

Quinolinic acid (QUIN), an endogenous neuroactive metabolite of tryptophan, administered i.c.v. in doses of 45, 90, 180, and 270 nmol in rabbits, demonstrated an excitatory action on the sleep-wake cycle and behaviour. Doses of 90 and 180 nmol completely abolished the paradoxical sleep phase and induced a 5-fold decrease in the duration of deep slow wave sleep (dSWS) in the first hour of the experiment. Light slow wave sleep (1SWS) duration was not altered. Sniffing behaviour was markedly activated by 180 nmol of QUIN. A dose of 270 nmol completely blocked sleep, diminished the restoration of sleep, induced panic behaviour and, in some animals, induced generalized tonic seizures. Data suggest an excitatory action of QUIN on NMDA receptors involved in the regulation of the sleep-wake cycle in the rabbit.