Sensitivity of circular and longitudinal uterine muscles to noradrenaline.
Spontaneous contractions of circular and longitudinal uterine muscles of rat and rabbit during estrogen domination were recorded in vitro isometrically. The circular muscles of both uteri contracted more frequently than the longitudinal muscles. Noradrenaline inhibited the spontaneous contractions of the longitudinal (ED50 = 5x10(-7) M) and circular (ED50 = 4.9x10(-6) M) rat uterine muscles. One molecule of noradrenaline bound 0.35 receptors in the circular and 0.63 receptors in the longitudinal rat muscles. Noradrenaline increased both amplitude and frequency of the rabbit uterine contractions (ED50 = 5.8x10(-9) M for the circular and 1x10(-7) M for the longitudinal muscles). One molecule of noradrenaline bound 0.63 receptors in the circular and 0.84 receptors in the longitudinal muscle of the rabbit uterus. The response of the longitudinal rabbit muscle to noradrenaline was influenced by D-600 to a larger degree than that of the circular muscle. The different sensitivity to noradrenaline of the circular and longitudinal uterine muscles may be explained by the different number of adrenoceptors and their binding sites as well as by some differences in calcium utilization.
D000818:Animals; D005260:Female; D005711:Gallopamil / Q000494:pharmacology; D009215:Myometrium / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013045:Species Specificity; D014590:Uterine Contraction / Q000187:drug effects*
D005711:Gallopamil; D009638:Norepinephrine