ABSTRACT
Axonal sprouting is a form of neuronal plasticity defined as the ability of spared axons to grow new ‘‘sprouts’’ to reinnervate neurons deprived of their normal inputs by a lesion of their afferents. Therefore, it fundamentally differs from the regrowth of an axon that has been injured (axonal regeneration). Axonal sprouting has been described more than 25 years ago in the brain of adult mammals (1). However, until very recently it was thought to be restricted to regions such as the hippocampus that still express a number of ‘‘immature’’ proteins in adulthood. This view has changed dramatically in the last few years with the demonstration that axonal sprouting can occur in adults in a number of brain regions, including the cerebral cortex and the striatum (2-5). The mechanisms that trigger axonal sprouting, however, remain largely unknown. In this review, we will focus on findings related to a model of axonal sprouting of the corticostriatal pathway that presents unique opportunities to elucidate these mechanisms.
