Dual projections of gonadotropin releasing hormone containing neurons to the interpeduncular nucleus and to the vasculature in the female rat.

Immunofluorescence for gonadotropin releasing hormone (GnRH) in combination with retrograde labeling from the interpeduncular nucleus, as well as from the vasculature confirms that, in the rat, certain GnRH neurons project from the septum-diagonal band to the interpeduncular nucleus. However, about one half of these GnRH neurons also project to fenestrated capillaries as evidenced by uptake and retrograde transport of both peripherally injected Fluoro-Gold and centrally injected rhodamine labeled microspheres. The results indicate that the endocrine effects of GnRH are exerted in part by neurons which simultaneously project to neurohemal contact zones and to areas in the brain which are involved in the regulation of certain behaviors. It is suggested that certain GnRH neurons can directly couple endocrine events with other intracerebral events, such as regulation of lordosis behavior.