Inhibition of the oestradiol-induced increase in adenohypophyseal weight and in hypothalamic and serum polyphenol oxidase activity by dopaminergic agonists.

The administration of oestradiol (oestradiol benzoate as an aqueous microcrystal suspension, Agofolin depot SPOFA, 1 mg i.m. twice a week) leads in rats to an increase in adenohypophyseal weight and in polyphenol oxidase activity in the serum (ceruloplasmin) and in the base of the brain (the floor of the third ventricle). The simultaneous peroral administration of the ergoline derivatives D-6-methyl-8-ergoline-(i)-yl acetic acid amide (Deprenon SPOFA) or N-(D-6-methyl-8-isoergolenyl)-N',N'-diethyl carbamide hydrogen maleate (lisuride, Lysenyl SPOFA) in a dose of 200 micrograms/rat/day markedly inhibited all three reactions. The two derivatives were equally effective. Inhibition of the increase in hypothalamic polyphenol oxidase activity, with resultant reduced disintegration of hypothalamic dopamine, may play a role in the mechanism of inhibition of the pituitary reaction to oestradiol caused by dopaminergic agonists. The agonists can also, of course, act like dopamine in the adenohypophysis itself.