PubMed1984
The effects of adrenoceptor agonists and antagonists on the contractile activity of cervical strips from early pregnant and nonpregnant women were studied. Noradrenaline and the alpha-adrenoceptor agonist, phenylephrine, had a stimulatory effect on smooth muscle activity. This response could be blocked totally by the alpha-adrenoceptor antagonist, phenoxybenzamine. Isoprenaline, known to be a beta-adrenoceptor agonist with some alpha-adrenoceptor activity, had stimulatory and inhibitory effects, whereas the beta 2-adrenoceptor agonist, terbutaline, exhibited a pure inhibitory action. The inhibitory effects of isoprenaline and terbutaline were totally blocked by the beta-adrenoceptor antagonist propranolol. In pregnant patients, the sensitivity to noradrenaline was significantly higher, and the inhibitory action of terbutaline was less pronounced, which indicated the predominance of alpha-receptor activity in the uterine cervix during pregnancy.