Anatomic relationships between aromatase and androgen receptor mRNA expression in the hypothalamus and amygdala of adult male cynomolgus monkeys

This study mapped the regional locations of cells expressing cytochrome P450 aromatase (P450AROM) and androgen receptor (AR) mRNAs in the adult male macaque hypothalamus and amygdala by in situ hybridization histochemistry using monkey‐specific cRNA probes. High densities of P450AROM and AR mRNA‐containing neurons were observed in discrete hypothalamic areas involved in the regulation of gonadotropin secretion and reproductive behavior. P450AROM mRNA‐containing neurons were most abundant in the medial preoptic nucleus, bed nucleus of the stria terminalis, and anterior hypothalamic area, whereas AR mRNA‐containing neurons were most numerous in the ventromedial nucleus, arcuate nucleus, and tuberomamillary nucleus. Moderate to heavily labeled P450AROM mRNA‐containing cells were present in the cortical and medial amygdaloid nuclei, which are known to have strong reciprocal inputs with the hypothalamus. Heavily labeled P450AROM mRNA‐containing cells were found in the accessory basal amygdala nucleus, which projects to the cingulate cortex and hippocampus, areas that are important in the expression of emotional behaviors and memory processing. In contrast to P450AROM, the highest density of AR mRNA labeling in the temporal lobe was associated with the cortical amygdaloid nucleus and the pyramidal cells of the hippocampus. All areas that contained P450AROM mRNA‐expressing cells also contained AR mRNA‐expressing cells, but there were areas in which AR mRNA was expressed but not P450AROM mRNA. The apparent relative differences in the expression of P450AROM and AR mRNA‐containing neurons within the monkey brain suggests that T acts through different signaling pathways in specific brain areas or within different cells from the same region. J. Comp. Neurol. 439:208–223, 2001. © 2001 Wiley‐Liss, Inc.