Independent brain stem sites for ventilatory neurogenesis

The purpose was to determine if independent ventilatory rhythms could be generated in each half of completely separated brain stems. In decerebrate, cerebellectomized, vagotomized, paralyzed, and ventilated cats, activities of phrenic, recurrent laryngeal (RLN), and/or hypoglossal nerves were monitored. Midsaggital brain stem divisions were performed by sections and lesions. Eupnea continued following divisions of mesencephalon and pons. Hypoglossal and phrenic activities were eliminated after sections approximating the obex. In most preparations, RLNs discharged with independent rhythms after completion of midsagittal brain stem section and a C1 transection. Independent rhythms were also obtained from each half of medulla following transections at the pontomedullary junction and at C1, and midsagittal medullary divisions. In other animals with transections between pons and medulla and at C1, synchronized RLN and hypoglossal activities persisted after sagittal medullary divisions, 2.0 mm lateral to midline contralaterally. Data demonstrate that there is more than one potential brain stem site for ventilatory neurogenesis. It is hypothesized that there are many such sites, possibly having pacemaker cells, in pons and medulla.