Brainstem afferents of the cholinoceptive pontine wave generation sites in the rat.

The present study was designed to investigate the distribution of brainstem neurons projecting to the pontine wave (P-wave)-generating sites in the rat. In six rats, biotinylated dextran amine (BDA) was microinjected into the physiologically identified cholinoceptive P-wave generation site. In all cases, microinjections of BDA in the cholinoceptive P-wave generating site resulted in retrograde labeling of cell bodies in many parts of the brainstem. The majority of those retrogradely labeled cells were in the pedunculopontine tegmentum, pontine reticular nucleus oralis, parabrachial nucleus, vestibular nucleus, and gigantocellular reticular nucleus. The results presented in this study provide anatomical evidence that the cholinoceptive P-wave generation site in the rat receives anatomical projections from other parts of the brainstem known to be involved in the REM sleep-generation mechanism.