Effects of Central Acting Drugs on Serum and Pituitary Prolactin Levels in Rats

Abstract

A single intraperitoneal injection of reserpine (R), chlorpromazine (C), alphamethyl- para-tyrosine (AMPT) or alpha-methylmeta-tyrosine (AMMT) in proestrous rats produced profound elevations in serum prolactin 30 min to 4 hr after injection. R, C and AMPT decreased pituitary prolactin concentration, whereas AMMT increased it. This indicates that these 4 drugs evoked rapid release of prolactin from the pituitary, and that AMMT also elicited rapid synthesis of prolactin. The increased release of pituitary prolactin may be related to inhibition by the drugs of catecholamine activity in the hypothalamus and/or to reduced hypothalamic PIF content. A single intraperitoneal injection of dopamine (D), epinephrine (E), norepinephrine (NE) or serotonin (S) had no significant effect on serum prolactin levels 1 or 2 hr after injection. D, E and NE also had no effect on serum prolactin values when injected intracarotidly. The higher doses of E and D but not NE produced a small decrease in pituitary prolactin concentration. The failure of these drugs given systemically to alter serum prolactin concentration may be due to a blood-brain barrier which prevents them from reaching a entralsite of action. The precise role of catecholamines in pituitary prolactin release remains to be defined.(Endocrinology87: 667, 1970)