LESIONS OF THE ROSTRAL DORSOLATERAL PONS HAVE NO EFFECT ON AFFERENT-EVOKED INHIBITION OF INSPIRATION

This study investigated a possible role of the rostral dorsolateral pons (including nucleus parabrachialis medialis and Kolliker-Fuse nucleus) in mediating several inspiratory inhibitions. These inhibitions included the transient inhibition of phrenic inspiratory motor output produced by stimulation of the superior laryngeal nerve (SLN), the intercostal nerve (ICN) or the phrenic nerve (PN), as well as the inspiratory termination produced by trains of stimuli delivered to the SLN or ICN. In decerebrate, decerebellate, paralyzed, and artificially ventilated cats, the inhibitions produced by stimulation of these nerves were observed before and after lesioning (either radiofrequency, n = 8, or electrolytic, n = 9) the dorsolateral pons. Delivery of stimulus trains to the SLN or the ICN continued to elicit inspiratory termination following pontine lesions with no significant change in the threshold. There were no significant effects of bilateral dorsolateral pontine lesions on the threshold, onset latency, or duration of the short-latency, transient inhibitions produced by SLN, ICN or PN stimulation. From these data, we conclude that the rostral dorsolateral pons is not required in the production of any of these inhibitory reflexes.