Atypical p-adrenoceptors mediate isoprenaline induced vasodilatation in the rabbit uterine vascular bed.

Abstract

β-Adrenoceptor subtype(s) mediating isoprenaline-induced vasodilator responses m the perfused rabbit uterine vascular bed was characterized. Isoprenaline induced dose-dependent reduction in perfusion pressure with -logED50 value of 5.8 ±0.1. Propranolol (10-6 M) had little or no effect on isoprenaline-induced vasodilatation. Similarly, cvanopindolol (10-6 M) did not antagonize the vasodilator response. CGP 12177, an agonist on β3- or β2- adrenoceptor mediated responses The results would indicate that isoproterenol-induced vasodilation in the perfused rabbit (oestrus or pregnant) uterine vascular bed was mediated by atypical β-adrenoceptors which may not be identical with those in adipose tissues or gastro-intestinal tract. In addition, the fact that pregnancy did not enhance isoprenaline-induced vasodilatation would suggest that these receptors may not be involved in the hyperaemia of pregnancy.