The feline carotid rete: vasomotor reactivity of isolated arteries

Vasomotor responses of arteries from the feline carotid rete were examined using a sensitive in vitro system. The vessel segments constricted in response to several vasoactive agents and putative neurotransmitters. Sympathomimetic agents (noradrenaline, adrenaline, oxymetazoline, phenylephrine), 5-hydroxytryptamine, histamine, angiotensin II, and prostaglandin F2 alpha all induced concentration-dependent contractile responses. The contractions induced by noradrenaline, 5-hydroxytryptamine, and histamine could be antagonized by phentolamine, methysergide, and mepyramine, respectively. Cholinomimetics (acetylcholine, carbacholine), vasoactive intestinal peptide and papaverine induced potent dilatory responses. The effect of carbacholine was shifted towards higher agonist concentrations by atropine. Dilatations, though small in magnitude, were found by application of adenosine, isoproterenol, and histamine. These results correlate well with the recent demonstration of autonomic nerves and indicate the occurrence of corresponding receptor sites in the walls of the carotid rete arteries.