AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 6 1291-R1297, Copyright © 1992 by American Physiological Society
Adrenergic vasomotor responses in nasal mucosa of hooded seals
L. P. Folkow
Department of Arctic Biology, University of Tromso, Norway.
In seals respiratory heat and water losses are restricted through nasal
heat exchange. The heat exchange efficiency is apparently controlled
through adjustments in the nasal mucosal blood flow rate and/or pattern. In
this study the adrenergic mechanisms involved in regulation of mucosal
blood flow were investigated. The nasal mucosal vasculature of 14 newly
killed hooded seal (Cystophora cristata) pups was perfused by a
constant-flow peristaltic pump with 37 degrees C oxygenated modified Krebs
solution via the sphenopalatine arteries. The effects of single-dose
injections of various drugs on resistance to flow were monitored with a
pressure transducer. Epinephrine, norepinephrine, alpha 1-adrenoceptor
agonist phenylephrine, alpha 2-agonist clonidine, beta 1-agonist
dobutamine, and beta 2-agonist terbutaline caused transient pressure
increases that were blocked by alpha-adrenoceptor antagonists. Papaverine
and vasoactive intestinal polypeptide induced vasodilatation, showing that
some basal vascular tone was present. Nevertheless, the beta 1- and beta
2-agonist isoproterenol had no effect on resistance, and none of the
beta-agonists attenuated the pressor responses to alpha-agonists. In
conclusion, adrenergic control of nasal mucosal blood flow in seals is
essentially exerted through alpha-adrenoceptor-mediated arteriolar
constriction, whereas beta-adrenoceptor-mediated dilatation seems to be of
little importance. It is suggested that such sympathoadrenergic vascular
mechanisms contribute to control nasal heat exchange efficiency in seals.
