17 beta-estradiol regulation of melanin-concentrating hormone and neuropeptide-E-I contents in cynomolgus monkeys: a preliminary study

Melanin-concentrating hormone (MCH) and neuropeptide-E-I (NEI) regulate sev eral behaviors and neuroendocrine functions in rats. Possible influence of these peptides on sexual behavior and reproduction in mammals other than ro dents prompted us to investigate: 1) The sites of synthesis of MCH and NEI in the brain of a non-human primate (M. fascicularis); 2) The effect, of 17 beta-estradiol (E-2) benzoate (E2B) on pro-MCH-derived peptide concentrati ons in the hypothalamus of the ovariectomized (OVX) cynomolgus monkeys (M. fascicularis). Expression of MCH mRNA and peptides was examined by Northern blotting, RT-PCR and RP-HPLC/RIA. Our results demonstrate that the MCH gen e is predominantly expressed in hypothalamus of macaque. E2B exposure of OV X monkeys provoked parallel phasic variations in the MCH-immunoreactivity ( IR) and NEI-IR. NEI-IR and to a lesser extent MCH-IR, showed a transient in crease (associated with the estradiol peak) at 30 h with a final rise of bo th MCH-IR and NEI-IR observed at the time (72 h post E2B) of the luteinizin g hormone (LH) surge. RP-HPLC analysis of peptide extracts revealed the pre sence, in addition to mature MCH and NEI, of different MCH-IR and NEI-IR fo rms in the hypothalami of control and E2B-treated monkeys. Taken together, our results indicated that hypothalamic MCH and NEI contents are regulated after E2B treatment and they suggest the possible involvement of these pept ides in the regulation of the pre-ovulatory midcycle LH surge in primates. (C) 1999 Elsevier Science Inc. All rights reserved.