LHRH neurons migrate into the trigeminal nerve when the developing olfactory nerve fibers are physically interrupted in chick embryos

Most LHRH neurons actively migrate from the olfactory epithelium to the for ebrain during embryonic days (ED) 3.5-8. When a small piece of the membrane filter was placed on the central course of the olfactory nerve in ED 3.5-5 chick embryos, LHRH neurons deviated from their regular migratory course a t ED 6.5-7.5 to follow a route along the PSA-NCAM-positive medial and later al nasal branches of the ophthalmic nerve of the trigeminal nerve. The olfa ctory nerve fibers which were specifically immunoreactive for somatostatin also deviated into the ophthalmic nerve. Enzymatic removal of PSA using end oneuraminidase did not interfere with the migration of LHRH neurons into th e ophthalmic nerve bundle of the trigeminal nerve. The presence of structur al supports seems to be primarily of importance in the migration of LHRH ne urons along the olfactory and trigeminal nerve bundles. PSA may be less imp ortant for the migration of the LHRH neurons along peripheral neural elemen ts. (C) 1998 Academic Press.