ORIGIN OF LUTEINIZING-HORMONE-RELEASING HORMONE (LHRH) NEURONS IN THE CHICK-EMBRYO - EFFECT OF THE OLFACTORY PLACODE ABLATION

A unilateral olfactory placodectomy resulted in the absence of luteinizing hormone-releasing hormone-immunoreactive (LHRH-ir) cells in the olfactory-forebrain axis of the operated side, whereas the development of the LHRH neuronal system was not disturbed on the unoperated side. In the embryos in which a fragment of the medial olfactory epithelium was spared the damage, a small number of LHRH-ir cells were detected in the nasal region of the operated side, where the lack of the central projection of the olfactory nerve caused stagnation of LHRH-ir cells, no ir-cells being found in the brain area. These results suggest that LHRH neurons originate in the olfactory placode and then migrate into the forebrain along the olfactory nerve.