The presence of adrenergic and cholinergic receptors in the celiac arteries of the cod, Gadus morhua , and the rainbow trout, Salmo gairdneri , has been investigated. Affinities and intrinsic activities of different catecholamines and acetylcholine have been determined from cumulative dose‐response curves. The pD 2 ‐value for acetylcholine was 6.62 ± 0.20 in the rainbow trout arteries, while the cod arteries only responded to acetylcholine in concentrations of 10 ‐ ‐ 2 M or more. In both species the potencies of the catecholamines producing contraction of the arteries were in the order adrenaline > noradrenaline > phenylephrine, while isoprenaline did not contract the preparations. In cod arteries competitive antagonism was obtained with yohimbine (pA 2 = 7.3), phentolamine (pA 2 = 8.0) and propranolol (pA 2 = 6.1), while phenoxybenzamine produced non‐competitive blockade of the response to noradrenaline (pM 50 = 6.9). It is concluded that although the rainbow trout celiac artery could possess double innervation, it is unlikely that a cholinergic vasomotor innervation plays any role in regulating the cod celiac artery. A solely adrenergic alpha receptor mediated innervation is therefore proposed for the cod celiac artery.
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Holmgren et al. (1974) studied this question.
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