Actions of some autonomic agents on the heart of the trout (Salmo gairdneri) with emphasis on the effects of adenyl compounds.

The effects of some autonomic agents including adrenaline, noradrenaline, dopamine, 5-hydroxytryptamine (5-HT), histamine, acetylcholine and adenyl nucleotides and nucleosides were examined on atria and ventricles of the trout (Salmo gairdneri). In atria, adrenaline, noradrenaline and dopamine produced positive chronotropic and negative or positive inotropic effects. Acetylcholine and 5-HT produced negative inotropic effects; 5-HT also produced small positive chronotropic effects. Adenosine and ATP produced negative inotropic and positive chronotropic effects; these effects were not antagonized by 8-phenyltheophylline nor were they potentiated by dipyridamole. alpha, beta-Methylene ATP, which is resistant to degradation, was inactive. These results suggest that, unlike all other vertebrate hearts studied, ATP and adenosine do not act via P1- or P2-purinoceptors. In the ventricle, adrenaline and noradrenaline produced positive inotropic effects. Acetylcholine and adenyl compounds had no direct action on contractility.