Activities of expiratory neurones of the Bötzinger complex during vocalization in decerebrate cats.

Repetitive electrical stimulation of the midbrain peri-aqueductal grey (PAG) terminates quiet breathing and initiates inspiration that precedes vocalization. To understand the neuronal mechanisms underlying this phenomenon, activities of expiratory neurones (n = 39) of the Bötzinger complex (BOT) were examined in decerebrate cats. Most augmenting expiratory (E-aug) neurones (20/22) of the BOT, including 15 bulbospinal neurones, decreased their activities (9/20) or ceased to discharge (11/20) after the onset of stimulation of the PAG. This suggests that suppression of E-aug neurones of the BOT, which project to phrenic motoneurones, results in disinhibition of these neurones, and, in turn, terminates expiration and initiates inspiration preceding vocalization.