Catecholestrogens in the brain: neuroendocrine integration.

In a series of experiments it has been shown that 4-hydroxyestradiol (4-OHE2) as well as 2-hydroxyestradiol (2-OHE2) are involved in regulatory mechanisms of LH secretion in the miniature pig. Two-hydroxyestrone (2-OHE1) and 1-hydroxyestradiol-benzoate (1-OHE2B), however, have no significant effects on LH secretion. Moreover the studies indicate a regional specificity in the action of 4-OHE2, 2-OHE2 and estradiol (E2). 4-OHE2 and 2-OHE2 decrease plasma LH when given into the ventromedial nucleus of the hypothalamus and increase plasma LH levels when microinjected into the dorsomedial nucleus of the hypothalamus. Whereas E2 affects LH secretion when it is given into the area dorsalis of the hypothalamus and fornix. In addition the experiments performed on female and male rats to measure the effects of 2-OHE2 and 2-OHE1 on turnover rates of dopamine, norepinephrine and epinephrine in the anterior mediobasal hypothalamus and medial preoptic area show that the effects of catecholestrogens may partly be mediated by catecholamines.