NEUROPEPTIDE-Y INNERVATION OF ESTROGEN-INDUCED PROGESTERONE RECEPTOR-CONTAINING DOPAMINE CELLS IN THE MONKEY HYPOTHALAMUS - A TRIPLE LABELING LIGHT AND ELECTRON-MICROSCOPIC STUDY

Light and electron microscopic triple immunostaining was performed on coronal vibratome sections prepared from the hypothalamus of ovariecto mized (OVX) and OVX plus estrogen-treated African green monkeys (Cerco pithecus aethiops). Immunoreactivity for progesterone receptors (PRs) and neuropeptide-Y (NPY) was visualized by a dark blue to black nickel diaminobenzidine reaction, while the tyrosine hydroxylase-containing perikarya were labeled with a light brown diaminobenzidine reaction. I n the OVX plus estrogen-treated material, 30% of the tyrosine hydroxyl ase-immunoreactive neurons contained PR-immunopositive nuclei. The maj ority of these cells were found in the central portion of the perivent ricular area, and a few could be observed in the anterior hypothalamus and the arcuate and dorsomedial hypothalamic nuclei. These tyrosine h ydroxylase-immunoreactive PR-containing cells were surrounded with NPY -immunoreactive axon terminals. A correlated electron microscopic anal ysis of the same sections revealed synaptic contacts between these NPY -immunoreactive boutons and the PR-containing tyrosine hydroxylase-imm unoreactive neurons. In contrast, in the OVX animals, no PR-containing tyrosine hydroxylase-immunoreactive neurons could be detected. In the se monkeys, the frequency of synaptic contacts between the NPY-immunor eactive axon terminals and tyrosine hydroxylase-immunopositive cells w as similar to that in the OVX plus estrogen-treated monkeys. These obs ervations indicate that in a population of hypothalamic dopamine cells , the presence of nuclear PRs is estrogen dependent, show that these c ells are innervated by NPY axons, and suggest that these estrogen-indu ced PR-containing dopamine neurons are involved in mediation of the ef fect of NPY on hypophyseal hormone secretion, including ovarian steroi d hormone-dependent LH and PRL release.