LHRH-Immunocytochemistry in the Nervus Terminalis of Mammals

Abstract

Apart from the chemoreceptor systems (olfactory, vomeronasal nerves), the septum of the vertebrate nose is innervated by the paired nervus terminalis. Fiber bundles run through rostromedial foramina of the cribriform plate and pass between and beneath the olfactory bulbs to enter the CNS in the area of the lamina terminalis and on the basal surface of the prosencephalon. The nervus terminalis in adult mammals is a ganglionated fiber plexus which obviously comprises two or more subpopulations of neurons. While one of these subpopulations is characterized by the occurrence of acetylcholinesterase (AchE), the other fraction of neurons expresses luteinizing hormone-releasing hormone (LHRH) and seems to be involved in mating behavior and reproduction (Jennes and Stumpf, 1980; Schwanzel-Fukuda and Silverman, 1980; Wirsig and Leonard, 1986; Schwanzel-Fukuda and Pfaff, 1989). During prenatal ontogenesis, LHRH is first detected in neurons of the terminalis nerve; this fact has led to the supposition that the nerve even helps to organize the brain-pituitarygonadal axis (Schwanzel-Fukuda et al., 1985, 1987, 1988; Jennes, 1989). From late fetal and early postnatal stages of rodents onward, the number of LHRH-immunoreactive (-ir) cells is reduced.