Journal of Applied Physiology, Vol 55, Issue 2 433-439, Copyright © 1983 by American Physiological Society
Independent brain stem sites for ventilatory neurogenesis
W. M. St John
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.
