QUANTITATIVE ESTIMATION OF ESTROGEN AND ANDROGEN RECEPTOR-IMMUNOREACTIVE CELLS IN THE FOREBRAIN OF NEONATALLY ESTROGEN-DEPRIVED MALE-RATS

Using quantitative immunocytochemical procedures, the total number of estrogen and androgen receptors was estimated in a large number of hyp othalamic and limbic nuclei of male rats, in which brain estrogen form ation was inhibited neonatally by treatment with the aromatase inhibit or 1,4,6-androstatriene-3,17-dione. The highest densities of estrogen receptor immunoreactivity were observed in the periventricular preopti c area and the medial preoptic area. Neonatally estrogen-deprived male s showed a higher estrogen receptor immunoreactivity than control male s in the periventricular preoptic area and the ventrolateral portion o f the ventromedial nucleus of the hypothalamus, i.e. those brain areas in which sex differences have been reported, with female rats showing a greater estrogen binding capacity than male rats. The highest densi ties of androgen receptor immunoreactivity were found in the septohypo thalamic nucleus, the medial preoptic area, the posterior division of the bed nucleus of the stria terminalis and the posterodorsal division of the medial amygdaloid nucleus. No significant differences in distr ibution or total numbers of androgen receptors were found between neon atally estrogen-deprived males and control males. These findings sugge st that neonatal estrogens, derived from the neural aromatization of t estosterone, are involved in the sexual differentiation of the estroge n receptor system in the periventricular preoptic area and the ventrom edial hypothalamus. The role of neonatal estrogens in the development of the forebrain androgen receptor system is less clear. (C) 1997 IBRO .