Journal of Applied Physiology, Vol 53, Issue 3 596-602, Copyright © 1982 by American Physiological Society
Aortic body chemoreceptor responses to dopamine, haloperidol, and pargyline
N. J. Smatresk and S. Lahiri
Aortic chemoreceptor activity, from single- or few-fiber afferent nerve
preparations, was measured in response to dopamine and a dopaminergic
blocker, haloperidol, in 18 anesthetized cats. In six of these cats the
effect of dopamine was assessed before and after inhibiting monoamine
oxidase (MAO) by pargyline. Intravenous dopamine infusion (7-14 microgram X
kg-1 X min-1) had a generally inhibitory effect on aortic chemoreceptor
activity, but the magnitude of this effect varied with arterial partial
pressure of O2 (Pao2) levels. The inhibitory effect of dopamine increased
as Pao2 levels fell, and at severely hypoxic Pao2 levels (below 30 Torr)
exogenous dopamine had no significant effect. The inhibitory effect of
dopamine also increased during hyperoxic hypercapnia. Blockade of dopamine
receptors in the aortic body by haloperidol-stimulated chemoreceptor
activity significantly during hypoxia, suggesting an O2-dependent release
of dopamine from the aortic body as Pao2 falls. Inhibition of MAO by
pargyline had no significant effect on the control rate of activity at any
level of Pao2 but augmented the inhibitory effect of exogenously
administered dopamine. These data indicate that MAO is not significantly
involved in the degradation of endogenous dopamine at the aortic receptor
sites, but may participate in the degradation of exogenous dopamine.
