Expiratory neurones of the rostral medulla: anatomical and functional correlates.

Intracellular recordings of the activities of 16 bulbar expiratory neurones of the rostral medulla were performed in decerebrate cats. Seven of these identified neurones were intracellularly injected with horse-radish peroxidase for morphological examination. We observed 3 categories of expiratory neurones including two pharyngeal motoneurones of the retrofacial nucleus, one with an augmenting, the other with a decrementing discharge pattern. Augmenting patterns were also observed in neurones ventromedial to the retrofacial nucleus and in another located 320 micron from the ventral surface of medulla. Their possible functions are discussed in relation to their anatomical location and morphology.