Response of medullary respiratory neurons to rostral pontine stimulation.

Respiratory neuron activity was recorded with microelectrodes in the vicinity of the nucleus tractus solitarius (NTS) and the rostral portion of nucleus retroambigualis (rNRA) in pentobarbital anesthetized cats with bilateral pneumothorax. Inspiratory NTS neurons receiving facilitatory volume inputs (inspiratory beta neurons) had short latency responses to threshold electrical stimulation in the ipsilateral vagus, but rarely to stimulation of the inspiratory inhibitory region of the rostral pons (pneumotaxic areas), suggesting that beta neurons do not appear to be the site of convergence of inspiratory inhibitory inputs. Inspiratory neurons in the rNRA did not have short latency facilitatory responses to vagal stimulation, but 15% responded to pneumotaxic area stimulation. One-third of the rNRA inspiratory neurons appeared to have spinal axons. None of those with spinal axons responded to pneumotaxic stimulation. Pneumotaxic area stimulation did consistently cause short latency evoked potentials in the rNRA. It is concluded that some rNRA-area propriobulbar inspiratory neurons may play a role in inspiratory inhibition by pneumotaxic mechanisms.