Androgen receptor immunoreactivity in the male and female Syrian hamster brain

To investigate potential mechanisms for sex differences in the physiologic response to androgens, the present study compared the hormonal regulation o f intracellular androgen receptor partitioning and the distribution of andr ogen receptor immunoreactivity in select brain regions from male and female hamsters. Androgen receptors were visualized on coronal brain sections. Tw o weeks after castration, androgen receptor immunoreactivity filled the neu ronal nuclei and cytoplasm in males and females. In gonad-intact males and females, androgen receptor immunoreactivity was limited to the cell nucleus . Whereas exogenous dihydrotestosterone prevented cytoplasmic immunoreactiv ity, estrogen at physiologic levels did not. These results suggest that nuc lear androgen receptor immunoreactivity in gonad-intact females is maintain ed by endogenous androgens, and that androgens have the potential to influe nce neuronal activity in either sex. However, sex differences in the number and staining intensity of androgen-responsive neurons were apparent in sel ect brain regions. In the ventral premammillary nucleus, ventromedial nucle us of the hypothalamus, and medial amygdaloid nucleus, androgen receptor st aining was similar in gonadectomized males and females. In the lateral sept um, posteromedial bed nucleus of the stria terminalis (BNSTpm), and medial preoptic nucleus, the number of androgen receptor-immunoreactive neurons wa s significantly lower in females (p < .05). Moreover, the integrated optica l density/cell in BNSTpm was significantly less in females (1.28 +/- 0.3 un its) than in males (2.21 +/- 0.2 units; p < .05). These sex differences in the number and staining intensity of androgen-responsive neurons may contri bute to sex differences in the behavioral and neuroendocrine responses to a ndrogens. (C) 1999 John Wiley & Sons, Inc.