LOCATION AND ANATOMICAL CONNECTIONS OF A PARADOXICAL SLEEP INDUCTION SITE IN THE CAT VENTRAL PONTINE TEGMENTUM

The brainstem mechanisms for the generation of paradoxical sleep are u nder considerable debate. Previous experiments in cats have demonstrat ed that injections of the cholinergic agonist carbachol into the oral pontine tegmentum elicit paradoxical sleep behaviour and its polygraph ic correlates, The different results on the pontine structures that me diate this effect do not agree. We report here that limited microinjec tions of a carbachol solution into the ventral part of the oral pontin e reticular nucleus in the cat induce, with a short latency, a dramati c, long-lasting increase in paradoxical sleep. Moreover, neuronal trac ing experiments show that this pontine site is connected with brain st ructures responsible for the different bioelectric events of paradoxic al sleep. These two facts suggest that the ventral part of the oral po ntine reticular nucleus is a nodal link in the neuronal network underl ying paradoxical sleep mechanisms.