TELENCEPHALIC AND DIENCEPHALIC ORIGIN OF RADIAL GLIAL PROCESSES IN THE DEVELOPING PREOPTIC AREA ANTERIOR HYPOTHALAMUS

Neuronal birth-dating studies using [H-3]thymidine have indicated that neurons in the preoptic area/anterior hypothalamus (POA/AH) are deriv ed primarily from progenitors in proliferative zones surrounding the t hird ventricle. Radial glial processes are potential guides for neuron al migration, and their presence and orientation during development ma y provide further information about the origin of cells in the POA/AH. In addition to determining the orientation of radial glial fibers, we examined the relationship of neurons with identified birth dates to r adial glial processes in the developing POA/AH of ferrets. Neuronal bi rth dates were determined by injecting ferret fetuses with bromodeoxyu ridine (BrdU) at several different gestational ages; brains were taken from ferret kits at subsequent prenatal ages. Sections were processed for immunocytochemistry to reveal vimentin or glial fibrillary acidic protein in radial glia, or BrdU-labeled cell nuclei. Numerous radial glial processes extended from the lateral ventricles through ventral p ortions of the septal region to the pial surface of the POA/AH. These fibers both encapsulated and coursed ventrally through and around the anterior commissure of ferret, rat, and mouse fetuses. These ventrally directed fibers were less evident at older ages. In double-labeled se ctions from ferrets, BrdU-labeled cells in the dorsal POA/AH were ofte n aligned in the same dorsal-ventral orientation as adjacent radial gl ial fibers. We suggest that a subset of neurons, originating in telenc ephalic proliferative zones, migrates ventrally along radial glial gui des into the dorsal POA/AH. (C) 1995 John Wiley & Sons, Inc.