The influence of beta-adrenergic antagonists on the adrenergic responses of the rat vas deferens.
The influence of beta-adrenergic antagonists (propranolol, pronethalol, alprenolol, isopropylmethoxamine, H 35/25, sotalol and practolol) on isotonic contractile responses to norepinephrine (NE) was studies. All drugs caused an increase in the maximum responses while depressant effects were seen only with high doses of propranolol, pronethalol and alprenolol. The enhancement of responses to NE was considerably greater at low concentrations of calcium (0.5-1.0 mM) than at high (8 mM) concentrations. The inhibitory effects of propranolol, pronethalol and alprenolol were diminished but not completely overcome by increasing calcium concentrations form 1.8 to 8 mM. Cumulative dose-response curves of calcium showed no increase in maximum responses although responses to low concentrations of calcium were augmented by sotalol and practolol. Evidence suggests that the enhancing effects of these drugs may be due to their facilitatory effect on calcium mobilization following alpha-adrenoceptor activation while their depressant properties probably reflect their membrane stabilizing properties.
The influence of beta-adrenergic antagonists on the adrenergic responses of the rat vas deferens. The influence of beta-adrenergic antagonists (propranolol, pronethalol, alprenolol, isopropylmethoxamine, H 35/25, sotalol and practolol) on isotonic contractile responses to norepinephrine (NE) was studies. All drugs caused an increase in the maximum responses while depressant effects were seen only with high doses of propranolol, pronethalol and alprenolol. The enhancement of responses to NE was considerably greater at low concentrations of calcium (0.5-1.0 mM) than at high (8 mM) concentrations. The inhibitory effects of propranolol, pronethalol and alprenolol were diminished but not completely overcome by increasing calcium concentrations form 1.8 to 8 mM. Cumulative dose-response curves of calcium showed no increase in maximum responses although responses to low concentrations of calcium were augmented by sotalol and practolol. Evidence suggests that the enhancing effects of these drugs may be due to their facilitatory effect on calcium mobilization following alpha-adrenoceptor activation while their depressant properties probably reflect their membrane stabilizing properties.