The effect of chemical sympathectomy on XXXX release at birth.

@entity1718 @entity742 @entity1425 @entity2922 @entity1063 @entity2955 @entity413 @entity6114
The precise source of circulating @entity2922 (CA) at birth and their role in circulatory adaptation is unclear. In order to determine the contribution of increased postganglionic sympathetic nerve activity to the CA surge at birth, we induced complete sympathectomy in near term fetal @entity742 prior to delivery by giving @entity2955 . Chronically catheterized fetal @entity742 received either @entity2955 (n = 5) or control infusion (n = 6). Chemical sympathectomy was verified by @entity6114 infusion. @entity742 were delivered at 142 +/- 1 days of gestation and serial plasma CA, heart rate, blood pressure, cardiac output, blood gases, blood @entity413 , and free @entity1718 , were measured before and for 4 h after delivery. Myocardial beta-adrenergic receptors and tissue CA concentration were determined following sacrifice. Baseline circulating @entity1063 (NE) values were lower in sympathectomized animals (183 +/- 45 versus 373 +/- 125 pg/ml, p less than 0.05) and epinephrine values were slightly higher (118 +/- 89 versus 48 +/- 1 pg/ml, NS). There was only a 2-fold increase in NE after cord cutting in sympathectomized animals while control animals had a 4-fold increase (peak NE values 354 +/- 121 versus 1305 +/- 363 pg/ml respectively, p less than 0.001). @entity1425 increased significantly in both groups and there were no significant differences between sympathectomized and control animals. Heart rate and blood pressure rose abruptly in both groups after cord cutting and there were no significant differences.(ABSTRACT TRUNCATED AT 250 WORDS)
