Relation between properties of adrenoceptors in mouse uterine smooth muscle and hormonal states

Dose-response relationships of epinephrine(EPI), noreepinephrine(NE), phenylephrine(PE) and isoproterenal(ISO),on isolated mice uteri at 4 hormonal states(estrogen primed, early pregnancy, late pregnancy and post-partum) were investigated. At estrogen primed and early pregnant states after propranolol(0.1 mM), the inhibitory effects of ISO were blocked whereas those of EPI, NE and PE reversed, leaving only the excitatory effect with pD2 values in the order of EPI>NE>PE>ISO. These results indicate the existence of alpha-adrenoceptor in mice uteri during these 2 states. No effects of these 4 sympathomimetic amines were observed in late pregnant and post-partum uteri after propranolol.In the presence of phentolamine(0.01 mM), these 4 amines only evoked inhibitory effects and the order of the pD2 values was ISO>EPI>NE>PE, indicating the existence of beta-adrenoceptor in the mice uteri during 4 hormonal states. The pD2 values of inhibitory effects of these 4 amines in early pregnant and post-partum mice uteri are greater than those in estrogen primed and late pregnant ones, suggesting that the number and/or the activity of beat-adrenoceptor is related to progesterone.Excitatory effects were elicited by EPI, NE and PE only during estrogen treatment and early pregnancy indicating that the presence of alpha-adrenoceptor may be related to estrogen.