Distinctive amygdala kindled seizures differentially affect neurobehavioral recovery and lesion-induced basic fibroblast growth factor (bFGF) expression

The differing effects of partial seizures on neurobehavioral recovery follo wing anteromedial cortex (AMC) injury in rats have previously been reported . Specifically, convulsive Stage 1 seizures evoked ipsilateral to the lesio n during the 6-day post-lesion critical period delayed recovery, while non- convulsive Stage 0 seizures were neutral. The present study was designed to elaborate on that research by examining several potential mechanisms for t he seizure-associated difference observed in functional outcome. Anesthetiz ed rats sustained unilateral AMC lesions followed by implantation of a stim ulating electrode in the amygdala ipsilateral (Expt. 1) or contralateral (E xpt. 2) to the lesion. Beginning 48 h after surgery, animals were kindled t o evoke Stage 0 or Stage 1 seizure activity during the critical period. Kin dling trials and afterdischarge (AD) were controlled to ascertain their rol e in functional outcome. Recovery from somatosensory deficits was assessed over a two-month period. The results revealed that (i) Stage 0 seizures did not impact recovery regardless of whether initiated ipsilateral or contral ateral to the lesion, (ii) Stage 1 seizures prevented recovery only when in itiated in the ipsilateral hemisphere during the post-lesion critical perio d, and (iii) the detrimental effect of Stage 1 seizures appears to be indep endent of the number of kindling trials provided and cumulative AD. Thus, t o determine why Stage 1 seizures evoked in the hemisphere ipsilateral to th e lesion impeded recovery, a separate group of animals (Expt. 3) were kindl ed accordingly and processed for c-Fos and basic fibroblast growth factor ( bFGF) immunohistochemistry. It was hypothesized that Stage 1 seizures evoke d in the injured hemisphere prevent recovery by blocking lesion-induced bFG F expression in structures shown to he important for recovery after cortex lesions (e.g., striatum). The results confirmed our hypothesis and suggest that thr seizure-associated inhibition of lesion-induced bFGF may alter the growth factor-mediated plasticity necessary for functional recovery. (C) 2 000 Elsevier Science B.V. All rights reserved.