Evidence for the presence of PS-OFF neurons in the ventromedial medulla oblongata of freely moving cats

Summary Recordings were made from 24 PS-OFF neurons, characterized by a slow rhythmic discharge rate during waking and slow wave sleep and a marked decrease in the firing rate during paradoxical sleep, in the ventromedial medulla oblongata of freely moving cats. These neurons were located in either the nuclei raphe magnus and pallidus or the neighboring reticular formation where serotonincontaining neurons are found in the cat. Two types of medullary PS-OFF neurons are described, and the descending projection and slow conduction velocity of some of these neurons are demonstrated.Supported by INSERM (U 52), CNRS (LA 162), and DGRST (Contract no. 79.7.1077)