Abstract
Summary
The influence of neural blocking agents injected into the third ventricle of the brain of female rats at the time of vaginal estrus with and without electrical stimulation of the ventral medial hypothalamus (VMH) on serum prolactin levels was examined 30, 45, 75 and 135 min after initiation of electrical stimulation. Prolactin levels of sham control animals decreased 30-40% from initial values. Electrical stimulation of hypothalamus did not alter the response from that of sham controls. Intraventricular administration of atropine alone gave a response similar to that of sham controls while electrical stimulation modified the extent of the decrease. The injection of propranolol, a β-adrenergic blocker, with and without electrical stimulation, increased serum prolactin 100-110%. Phenoxybenzamine, an α-adren-ergic blocker, alone resulted in a gradual but progressive increase in serum prolactin levels. Electrical stimulation of phenoxybenzamine-injected animals prevented the rise in serum prolactin observed for drug treatment alone.
Rat prolactin used for iodination and as standards in the RIA was received as a gift from Dr. A. F. Parlow through the Endocrine Study Section of the National Institute for Arthritis and Metabolic Diseases. Propranolol (Inderal), and phenoxybenzamine (Dibenzyline) were received as gifts from Ayerst Laboratories Inc. and Smith, Kline and French Laboratories, Inc., respectively.
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