Role of acetylcholinesterase in the development of axon tracts within the embryonic vertebrate brain

In the developing vertebrate brain, acetylcholinesterase (AChE) expression coincides temporally with axon tract formation. Although AChE promotes neur ite outgrowth iii vitro, the role of this molecule in the development of ax on tracts in vivo is unknown. To address this question, we examined the eff ects of the AChE inhibitor, BW284C51, on the formation of the early scaffol d of axon tracts in the embryonic Xenopus brain. In exposed Xenopus brain p reparations, axone elongate and establish a normal topography of axon tract s. However, when brains were exposed to BW284C51, the thickness of the majo r longitudinal axon tract, the tract of the post-optic commissure decreased in a dose-dependent manner. When BW284C51 was removed from the culture med ia axon tract development returned to normal within 5 h. These findings pro vide the first evidence for a non-classical role of AChE in the initial for mation of axon tracts within the developing vertebrate brain. (C) 1999 ISDN . Published by Elsevier Science Ltd. All rights reserved.