Gonadal influences on the sexual differentiation of monoamine oxidase type A and B activities in the rat brain.
The sex-dependent differentiation of monoamine oxidase (MAO) in the hypothalamus of 60-day-old, Charles River rats was found to involve only type A (MAO-A), and not type B (MAO-B) enzyme. In vivo inhibition of type A by clorgyline, and type B by (--)deprenyl, however, tended to decrease the specific activity of both types of MAO to a smaller extent in the female than in the male hypothalamus. When masculinization was prevented by neonatal administration of estradiol (E) to males, hypothalamic MAO-A and MAO-B activities increased in both control and MAO-inhibited rats. Androgenization of females, however, had little effect on the MAO activity. Whereas the effects of neonatal estrogenization were attributable neither to a direct influence of E nor to a sexual difference in the peripheral clearance of the MAO-inhibitor used, single, high doses of steroids to adult, but not to newborn rats, did acutely affect the kinetics of MAO-A. The activity of MAO-A was also decreased by high concentrations of E or TS in vitro. The imprinting for patterns of hypothalamic MAO-A and MAO-B in the two sexes results, probably, from genetic predetermination. Neonatal changes in the homeostasis of gonadal hormones may result in type-MAO nonspecific effects in adulthood, whereas the short-term effects of high concentrations of steroids may be selective for the A form.
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D003010:Clorgyline / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007031:Hypothalamus / Q000201:enzymology; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008995:Monoamine Oxidase / Q000145:classification / Q000378:metabolism*; D051381:Rats; D012737:Sex Factors; D012741:Sexual Maturation; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013739:Testosterone / Q000494:pharmacology
D007527:Isoenzymes; D013739:Testosterone; D004958:Estradiol; D013385:Succinate Dehydrogenase; D008995:Monoamine Oxidase; D003010:Clorgyline