Journal of Applied Physiology, Vol 71, Issue 6 2274-2282, Copyright © 1991 by American Physiological Society
Role of caudal ventrolateral medulla in reflex and central control of airway caliber
P. A. Padrid, J. R. Haselton and M. P. Kaufman
Department of Internal Medicine, University of California, Davis 95616.
We investigated the role played by the caudal ventrolateral (CVL) medulla
in the reflex and central neural control of airway caliber in
chloralose-anesthetized dogs. Changes in total lung resistance were evoked
by four different stimuli. These changes were compared before and after
bilateral injection of either ibotenic acid (75 nl; 100 mM) or cobalt
chloride (75 nl; 50 mM) into the CVL medulla. The four stimuli used to
change lung resistance were static muscular contraction, electrical
stimulation of thin fiber afferents in the sciatic nerve, electrical
stimulation of the posterior diencephalon, and hypoxia. The first three
stimuli have been shown to decrease total lung resistance, whereas the
latter stimulus has been shown to increase resistance. We found that
injection of both ibotenic acid, which destroys cell bodies but not fibers
of passage, and cobalt, which prevents synaptic transmission, either
abolished or greatly attenuated the decrease in total lung resistance
evoked by static contraction, by sciatic nerve stimulation, and by
posterior diencephalic stimulation. We also found that injection of
ibotenic acid and cobalt attenuated the reflex increase in lung resistance
evoked by hypoxia. In control experiments, we found that bilateral
injection of ibotenic acid into the dorsal medulla had no effect on the
changes in total lung resistance evoked by these four stimuli. We conclude
that the CVL medulla plays an important role in the reflex and central
control of airway caliber.
