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ArticleTitle	Two Distinct Populations of Neurons Expressing Nitric Oxide Synthase mRNA in the Female Rat Preoptic Area: Site Specific Changes Induced by Sex Steroids
AuthorList	Tamaki Ishihara1, Tsutomu Araki1 and Yasuo Sakuma2
Affiliation	Departments of Obstetrics & Gynecology1 and Physiology2, Nippon　Medical School
Language	EN
Volume	68
Issue	4
Year	2001
Page	328-334
Received	March 2, 2001
Accepted	March 28, 2001
Keywords	in situ hybridization, juvenile rat, organum vasculosum of the lamina terminalis, preoptic area, nitric oxide synthase
Abstract	Non-isotopic in situ hybridization histochemistry in the basal forebrain of gonadectomized juvenile female rats visualized neuronal nitric oxide synthase (nNOS) mRNA in two distinct cellular populations, one in the organum vasculosum of the lamina terminals (OVLT) and the other in the rostral preoptic area at the level of the anteroventral periventricular nucleus (rPOA). In the rPOA, digoxigenin-labeled nNOS mRNA positive cells were in close proximity to the cell body of gonadotropin-releasing hormone (GnRH) -immunoreactive neurons. In the OVLT, the labeled cells were in an area rich in GnRH fibers. In the frontal section of the rPOA, the labeled cells were distributed in an inverted V-shaped area over the third ventricle. Combined treatment with estradiol and progesterone caused a significant reduction in the number of nNOS mRNA positive cells in the inverted V-shaped area in the female rat rPOA. The treatment induced a luteinizing hormone surge at the time of sacrifice. In the OVLT, ovarian steroids had no effect on nNOS mRNA expression. The results indicate that nNOS mRNA expression in the rPOA is regulated by ovarian steroids in a site-specific manner.
Correspondence to	Tamaki Ishihara, MD, Department of Obstetrics & Gynecology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan