ACTIVITIES OF EXPIRATORY NEURONS OF THE BOTZINGER COMPLEX DURING VOCALIZATION IN DECEREBRATE CATS

REPETITIVE electrical stimulation of the midbrain periaqueductal grey (FAG) terminates quiet breathing and initiates inspiration that preced es vocalization. To understand the neuronal mechanisms underlying this phenomenon, activities of expiratory neurones (n=39) of the Botzinger complex (BOT) were examined in decerebrate cats. Most augmenting expi ratory (E-aug) neurones (20/22) of the BOT, including 15 bulbospinal n eurones, decreased their activities (9/20) or ceased to discharge (11/ 20) after the onset of stimulation of the FAG. This suggests that supp ression of E-aug neurones of the BOT, which project to phrenic motoneu rones, results in disinhibition of these neurones, and, in turn, termi nates expiration and initiates inspiration preceding vocalization.