ELEVATED EXPRESSION OF B-50 (GAP-43) -mRNA IN A SUBPOPULATION OF OLFACTORY BULB MITRAL CELLS FOLLOWING AXOTOMY

Using in-situ hybridization method. We studied B-50 (GAP-43) mRNA expression following lesion of olfactory bulb mitral cells in rats. Expression of B-50 mRNA in approximately 40% of the mitral cells was upregulated in response to transection of their axons in the lateral olfactory tract (LOT). Enhanced expressin persisted for 10 days postlesion but than declined to control levels by 4 weeks after the lesion. A large proportion of the mitral cells gradually degenerated subsequent to LOT transection. Thus, a subpopulation of mitral cells maintain their ability to upregulate B-50, a protein characteristic of growing axons, but enhanced B-50 expression is not accompanied by regeneration of the severed LOT.