Journal of Applied Physiology, Vol 65, Issue 5 2004-2010, Copyright © 1988 by American Physiological Society
Effects on respiratory pattern of focal cooling in the medulla of the dog
M. Adams, T. Chonan, N. S. Cherniack and C. von Euler
Department of Surgery, Case Western Reserve University, Cleveland, Ohio 44106.
Studies in cats have shown that, in addition to respiratory neuron groups
in the dorsomedial (DRG) and ventrolateral (VRG) medulla, neural structures
in the most ventral medullary regions are important for the maintenance of
respiratory rhythm. The purpose of this study was to determine whether a
similar superficially located ventral region was present in the dog and to
assess the role of each of the other regions in the canine medulla
important in the control of breathing, in 20 anesthetized, vagotomized, and
artificially ventilated dogs, a cryoprobe was used to cool selected regions
of the medulla to 15-20 degrees C. Respiratory output was determined from
phrenic nerve or diaphragm electrical activity. Cooling in or near the
nucleus of the solitary tract altered timing and produced little change in
the amplitude or rate of rise of inspiratory activity; lengthening of
inspiratory time was the most common timing effect observed. Cooling in
ventrolateral regions affected the amplitude and rate of rise of
respiratory activity. Depression of neural tidal volume and apnea could be
produced by unilateral cooling in two ventrolateral regions: 1) near the
nucleus ambiguus and nucleus para-ambiguus and 2) just beneath the ventral
medullary surface. These findings indicate that in the dog dorsomedial
neural structures influence respiratory timing, whereas more ventral
structures are important to respiratory drive.
