Region-specific sprouting of crossed corticofugal fibers after unilateral cortical lesions in adult mice

Long considered to be limited to early development or restricted adult brain regions in mammals, axonal sprouting of spared axons into denervated brain areas now appears more widespread in the adult mammalian brain. However, its extent and mechanisms remain poorly understood. In this study, we show that robust sprouting of corticofugal axons occurs in the dorsolateral striatum but not the red nucleus of adult mice after unilateral lesions of the sensorimotor cortex induced either by mechanical removal or by thermocoagulation of pial blood vessels. These results show that local factors are critical for axonal sprouting in adult brain. They also extend previous findings in rats to a species readily amenable to genetic analysis in order to elucidate the mechanisms of this effect.