title: Adrenergic vasomotor responses in nasal mucosa of hooded seals.
abstract: 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.
authors: Department of Arctic Biology, University of Tromsø, Norway.
authors: L P
authors: LP
authors: Folkow
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology; D009297:Nasal Mucosa / Q000098:blood supply / Q000294:innervation / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D046048:Seals, Earless / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013566:Sympathomimetics / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects; D014666:Vasomotor System / Q000502:physiology*
chemical_list: D013566:Sympathomimetics; D009638:Norepinephrine; D004837:Epinephrine