Immunohistochemical detection of progestin receptors in hypothalamic β-endorphin and substance p neurons of steroid-treated monkeys

Cynthia L. Bethea, Andrea A. Widmann

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    25 Scopus citations


    Progesterone (P) acts in the central nervous system to increase prolactin secretion in estrogen (E)-primed female monkeys. β-Endorphin (BE) and Substance P (SP) are two hypothalamic peptides which increase prolactin secretion when administered to rats and monkeys. Studies were performed to determine if P acts on these two potential prolactin-releasing systems. The presence of a nuclear steroid receptor defines the cell as a target for the cognate hormone. Therefore, the hypothalamic populations of BE and SP neurons were examined for the presence and regulation of nuclear progestin receptors (PR) in spayed, E-treated (28 days) and E + P-treated monkeys (14 days E + 14 days E + P). Hypothalamic blocks were prepared after perfusion fixation with 4% paraformaldehyde. Cryosectioning (10 �m) was followed by double immunocytochemistry (ICC) for PR (black nuclear stain) and either BE or SP (brown cytoplasmic stain). Sections were processed for ICC at 100- or 200-�m intervals through the hypothalamic block. Peptidergic neurons with and without PR were counted in each section. The E + P-treated monkeys exhibited a significant increase in serum prolactin. BE neurons were found only in the arcuate nucleus (ARC) and median eminence (ME). The colocalization of BE and PR equaled 2% in spayed controls, 21 % in the E-treated group and 25 % in the E + P-treated group. SP neurons were located in a dorsomedial hypothalamic (DMH) subpopulation which extended caudally under the mammary nuclei and in a subpopulation located in the ARC and ME. Neither the DMH or submamillary SP neurons contained PR. The percent colocalization of SP and PR in the ARC/ME equaled 5, 26 and 10% in the spayed, E- and E + P-treated groups, respectively. The decrease in PR + SP colocalization with P treatment is probably due to a decrease in SP and not to a decrease in PR immunoreactivity. In summary, E treatment induced PR in BE and SP neurons. Addition of P to the E treatment did not alter the expression of PR in BE neurons, but PR colocalization decreased in SP neurons. Therefore, it is unlikely that SP neurons could transduce the action of P on prolactin secretion in primates, but BE neurons may play an intermediary role.

    Original languageEnglish (US)
    Pages (from-to)132-141
    Number of pages10
    Issue number2
    StatePublished - 1996


    • Gonadal steroid receptors
    • Gonadal steroids
    • Primates
    • Substance P
    • β-Endorphin

    ASJC Scopus subject areas

    • Endocrinology, Diabetes and Metabolism
    • Endocrinology
    • Endocrine and Autonomic Systems
    • Cellular and Molecular Neuroscience


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