ABSTRACT
Following a unilateral anteromedial cortex lesion, a critical period of 12 h to 6 days exists during which the recovery process is exquisitely vulnerable to manipulation. Certain anti-convulsant drugs, as well as convulsive seizures impede recovery when administered during, but not after, the critical period. The mechanisms underlying these behavioral phenomena have not been delineated. Thus, the present study was designed to determine potential mechanisms underlying and responsible for the critical period. To this end, we measured the immunoreactivity of two important markers of the post-injury response cascade, c-Fos and bFGF, at designated times after a unilateral anteromedial cortex lesion. These temporal patterns of expression in the perilesional cortex and ipsilateral dorsal striatum were mapped onto functional recovery patterns. Within the critical period, c-Fos was dramatically elevated through 48 h after the lesion, while bFGF peaked later, on day 6. Upregulation of these markers preceded recovery from somatosensory deficits, which was most dramatic after post-operative day 9 and complete by day 23. Early post-lesion expression of c-Fos may contribute to lesion-induced bFGF expression, which through its neurotrophic properties could be responsible for subsequent functional recovery. Gaining a similar understanding of the critical period following human traumatic brain injury could be an important first step toward improved treatment strategies and neurobehavioral outcome.
