GRADED EXPRESSION OF netrin-1 BY SPECIFIC NEURONAL SUBTYPES IN THE ADULT MAMMALIAN STRIATUM

Netrins are a family of secreted proteins that function as axon guidance cues during neural development. High levels of netrin-1 expressed by the embryonic ganglionic eminence, the precursor of the adult striatum, direct axons that pioneer the internal capsule. Here we describe netrin-1 expression by neurons distributed throughout the striatum of the adult mouse. Differences were detected in the number and type of neurons expressing netrin-1 in different regions of the striatum. Most neurons in the ventral striatum, including projection neurons and cholinergic interneurons, express netrin-1. In contrast, netrin-1 expression is largely limited to cholinergic interneurons in the dorsal striatum, and the proportion of cholinergic interneurons that express netrin-1 decreases along rostral-caudal and ventral-dorsal axes. Regional differences in expression in the adult striatum suggest that netrin-1 not only influences the development of striatal circuitry but may also participate in the maintenance and plasticity of connections in the adult brain. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.