Effects of injections of monoamine oxidase inhibitor or saline into the uterus in late pregnancy on uterine catecholamine levels related to abnormal parturition in rats.
Injection of a monoamine oxidase (MAO) inhibitor (nialamide) into the uterus of an anaesthetized and laparotomized rat on day 20 of pregnancy severely disturbed parturition. Injection of the solvent (0-9% isotonic NaCl solution) at the same stage of gestation produced the same but less frequent disturbances. When the rats were injected on days 19 or 21, impairment was less marked than on day 20. Therefore, day 20 seems to be a critical period for the onset of parturition. Injection of Ringer solution into the uterus on day 20 had effects analogous to those of saline injection at the same stage. Anaesthesia induced with ether, laparotomy of the pregnant rat on day 20, and handling of the uterine horns without injection of either Ringer or NaCl also disturbed parturition in 70% of the rats treated. Nevertheless, disorders were not as severe as those after injection. Laparotomy alone on day 20 did not disturb parturition. The effects on parturition of a saline injection into the uterus on day 20 were greatly decreased when the injection was performed on pregnant rats adrenalectomized on day 14, or on pregnant rats pretreated on days 18 and 19 with an agent blocking the adrenergic beta receptors (propranolol); 70-80% of the treated rats had normal deliveries. In control rats, uterine catecholamine levels were markedly modified between days 21 and 22 of gestation. These changes did not occur in rats injected with MAO inhibitor or saline.
D000315:Adrenalectomy; D000818:Animals; D002395:Catecholamines / Q000032:analysis*; D004837:Epinephrine / Q000032:analysis; D005260:Female; D007743:Labor, Obstetric / Q000187:drug effects*; D009526:Nialamide / Q000494:pharmacology*; D009638:Norepinephrine / Q000032:analysis; D011247:Pregnancy; D011273:Pregnancy, Prolonged; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology*; D013997:Time Factors; D014599:Uterus / Q000032:analysis / Q000187:drug effects*
D002395:Catecholamines; D012965:Sodium Chloride; D011433:Propranolol; D009526:Nialamide; D009638:Norepinephrine; D004837:Epinephrine