Effects of catecholamines on isolated systemic and branchial vascular beds of the cod,Gadus morhua

Summary

The effects of catecholamines on the vascular resistance of the gills, the gas gland and the tail of the Atlantic cod, were studied in isolated preparations perfused at a constant pressure. Adrenaline caused a biphasic response of the gill vasculature with an initial constriction followed by a dilation. The noradrenaline response was usually dilatory, but constrictory responses at all or some concentrations were occasionally seen in some specimens. The branchial dilation was caused by adrenaline concentrations even lower than those found in “normal” cod plasma (30 nM). The gas gland and the tail vasculature were constricted by both adrenaline and noradrenaline. A flow reduction in the isolated preparations of about 10% at concentrations of adrenaline equalling that in “normal” cod plasma (30 nM) was increased to about 30% (tail) or 45% (gas gland) at concentrations of adrenaline similar to that found in cod plasma during “stress” (300 nM).

The constrictory responses to adrenaline and noradrenaline were antagonized in all preparations by the alpha adrenoceptor antagonist, phentolamine (10⁻⁶ M) and the dilatory response of the branchial vasculature to these agonists was reduced or abolished by propranolol (10⁻⁶ M).

It is concluded that adrenaline, in the concentrations found in cod plasma at rest and after “stress”, has pronounced effects on the organs studied, especially the gill vasculature, and may thus contribute to the overall control of the circulatory system. The branchial vasculature will also be affected by changes in noradrenaline concentration which occur in animals at rest and under “stress”.