SEPARATION OF MULTIPLE FUNCTIONS IN VENTILATORY CONTROL OF PNEUMOTAXIC MECHANISMS

Multiple functions have been ascribed to the pontile pneumotaxic cente r. We hypothesized that these function s might be separable among neur ons in different regions. In decerebrate, vagotomized, paralyzed and v entilated cats, activities of the phrenic and triangularis sterni nerv es were recorded. Microinjections of kainic acid were used to destroy neurons. Neurons in the rostrolateral tegmentum at the ponto-mesenceph alic border controlled the duration of neural inspiration. Expiratory duration was controlled by neurons in the more caudal nucleus parabrac hialis medialis and Kolliker-Fuse nucleus. Ventilatory responses to hy percapnia were depressed following injections of kainic acid into regi ons controlling either inspiratory or expiratory durations. The phases of expiration were regulated by two groups of neurons, located medial and lateral in the rostral pons. We conclude that rostral pontile and mesencephalic mechanisms control multiple aspects of the eupneic vent ilatory cycle. There mechanisms are served by neurons in separable ana tomical regions.