Lack of Functional Influence by Prenalterol through α₁‐Adrenoceptors in Rat Myocardium

Abstract

Some of the cardiac properties of the partial P-agonist prenalterol may indicate a contribution from a,adrenergic stimulation. We therefore studied whether prenalterol interacted with a]-adrenoceptors in rat myocardium. Combination with propranolol did not reveal an al-adrenergic inotropic effect of prenalterol in papillary muscles. Neither did prenalterol block the a]-adrenergic response to phenylephrine. In myocardial cells, prenalterol inhibited 'H-prazosin binding to a]-adrenoceptors only at very high concentrations. Prenalterol thus exhibited no functionally important interactions with al-adrenoceptors in myocardium, and its properties cannot be accounted for in terms of contribution from al-adrenergic effects.

Characterization of Mechanical Effects and β‐Adrenoceptor Binding of Prenalterol in Rat Myocardium

“…This was in contrast to the lack of effect on the response to isoprenaline. These results did not indicate an a-adrenergic component of the inotropic response to prenalterol, in agreement with other more direct studies (Aass et al 1983). The present finding may, however, indicate an interaction between a phentolamine sensitive receptor (possibly an a-adrenoceptor) and P-adrenoceptors in the response to prenalterol.…”