Effect of noradrenaline on circulation in the genital tract of early and late pregnant guinea-pigs.
Noradrenaline infusions were given to anaesthetized guinea-pigs in early (19--23 days) and near-term (61--66 days) pregnancy. Radioactive microspheres (15 micrometers) were used to determine blood flow in various regions of the genital tract. In late gestation, a 10-min intravenous infusion of 1 micrograms noradrenaline/min/kg elicited moderate increases in vascular resistance that were counteracted by the pressor response. Uterine and placental blood flow remained unchanged, although there was a 27% decrease in perfusion of the uterine cervix and a fall of 19% in vaginal blood flow. In early pregnant guinea-pigs, blood pressure rose but vascular resistance was unaffected, resulting in an augmentation of placental blood flow. During infusion of 10 micrograms noradrenaline/min/kg, the vasonconstrictor response in late pregnancy was accentuated, and a strong decrease in tissue perfusion was noted in the placenta (-36%), uterine horns (-39%), cervix (-70%) and vagina (-56%). At the higher rate of noradrenaline infusion, vascular resistance also increased in the genital tract of early pregnant animals, although to a lesser extent than in late pregnancy. The results indicate an enhancement of the vasoconstrictor response to circulating catecholamines in near-term pregnancy.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D005260:Female; D005836:Genitalia, Female / Q000098:blood supply*; D006168:Guinea Pigs; D009638:Norepinephrine / Q000494:pharmacology*; D010053:Ovary / Q000098:blood supply; D010920:Placenta / Q000098:blood supply; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects; D014599:Uterus / Q000098:blood supply; D014621:Vagina / Q000098:blood supply; D014655:Vascular Resistance / Q000187:drug effects
D009638:Norepinephrine