SUPERSENSITIVITY OF ANTERIOR PITUITARY DOPAMINE RECEPTORS INVOLVED IN THE INHIBITION OF PROLACTIN SECRETION FOLLOWING DESTRUCTION OF THE MEDIAL BASAL HYPOTHALAMUS1
The medial basal hypothalamus of ovariectomized rats was destroyed using a modified Halasz knife. Large increases in prolactin secretion were observed 1 and 14 days following the lesions. Long- and short-term lesioned animals were anesthetized with chloral hydrate and treated with various doses of apomorphine (0.05, 0.2, 2, 5 mg/kg). Blood samples were obtained before and 10, 30 and 60 min after the injection. Both the 0.05 and 0.2 mg/kg doses caused significantly greater and longer-lasting inhibition of prolactin in long-term than in short-term lesioned animals. Since the MBH [medial basal hypothalamus] was totally destroyed, this study suggests that the anterior pituitary dopamine receptors involved in the inhibition of prolactin secretion become supersensitive in long-term lesioned rats.