Supersensitivity of anterior pituitary dopamine receptors involved in the inhibition of prolactin secretion following destruction of the medial basal hypothalamus

The medial basal hypothalamus of ovariectomized rats was destroyed using a modified Halsz 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 minutes 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 was totally destroyed this study suggests that anterior pituitary dopamine receptors involved in the inhibition of prolactin secretion become supersensitive in long-term lesioned rats.