DISTRIBUTION OF ESTROGEN RECEPTOR-IMMUNOREACTIVE CELLS IN MONKEY HYPOTHALAMUS - RELATIONSHIP TO NEURONS CONTAINING LUTEINIZING-HORMONE-RELEASING HORMONE AND TYROSINE-HYDROXYLASE

The precise sites and mechanisms by which gonadal steroids influence t he activity of neuroendocrine cells controlling pituitary hormone secr etion are poorly understood. The present study has determined the dist ribution of estrogen receptor (ER)-immunoreactive cells in the monkey hypothalamus and examined whether ERs are expressed by luteinising hor mone releasing hormone (LHRH)-and/or dopamine-containing neurones. The distribution of ER-immunoreactive cells was determined in ovariectomi sed (n = 2) and estrogen plus progesterone-treated (n = 2) cynomolgus macaques and in a single ovariectomised African green monkey. Large nu mbers of cells immunoreactive for the ER were detected in the preoptic area, bed nucleus of the stria terminalis, periventricular area and v entromedial and arcuate nuclei of all monkeys irrespective of the ster oid status. Smaller numbers of ER-immunoreactive cells were found in t he paraventricular, but not supraoptic nucleus. Double-labeling experi ments in sections from ah 5 monkeys revealed that none of the 432 LHRH neurons examined possessed detectable ER immunoreactivity. Neurones s tained for tyrosine hydroxylase (TH) were identified in the A11, A12, and A14 cell groups and, although A11 and A12 neurones were intermingl ed amongst and found adjacent to ER-immunoreactive cells, none of the 1,652 TH-immunoreactive cells examined contained ER immunoreactivity. These results show that ER-immunoreactive cells in the monkey hypothal amus are distributed in a manner similar to that observed in other mam malian species although not all brain regions reported to contain prog esterone receptors (PRs) in these species of monkey were found to expr ess ERs. The double-labelling experiments provide further evidence tha t LHRH neurones do not possess ERs and indicate that, as in other spec ies, estrogen influences on primate LHRH neurones are indirect and/or non-genomic in nature. Unlike the rat and sheep, no evidence was found for ER immunoreactivity in hypothalamic dopaminergic neurones of the monkey. The discrepancy in ER and reported PR receptor localisation wi thin specific hypothalamic nuclei as well as in dopaminergic neurones raises the possibility that not all PR-containing cells may express ER s in the primate hypothalamus.