Gonadotropin-releasing hormone immunoreactivity in the adult and fetal human olfactory system

Studies in fetal brain tissue of rodents, nonhuman primates and birds have demonstrated that cells containing gonadotropin-releasing hormone (GnRH) mi grate from the olfactory placode across the nasal septum into the forebrain . The purpose of this study was to examine GnRH neurons in components of th e adult and fetal human olfactory system. In the adult human brain (n = 4), immunoreactive GnRH was evident within diffusely scattered cell bodies and processes in the olfactory bulb, olfactory nerve, olfactory cortex, and ne rvus terminalis located on the anterior surface of the gyrus rectus. GnRH-i mmunoreactive structures showed a similar distribution in 20-week human fet al brains (n = 2), indicating that the migration of GnRH neurons is complet e at this time. In 10-11-week fatal brains (n = 2), more cells were noted i n the nasal cavity than in the brain. Our data are consistent with observat ions made in other species, confirming olfactory derivation and migration o f GnRH neurons into the brain from the olfactory placode. (C) 1999 Elsevier Science B.V. All rights reserved.