Forelimb use after focal cerebral ischemia in rats treated with an alpha 2-adrenoceptor antagonist

Atipamezole, a selective alpha(2)-adrenoceptor antagonist, enhances recovery of sensorimotor function after focal cerebral ischemia in rats. The aim of the present study was to further characterize the effects of atipamezole treatment combined with enriched-environment housing in ischemic rats by evaluating spontaneous exploratory activity in the cylinder test. The right middle cerebral artery (MCA) of rats was occluded for 120 min using the intraluminal filament method. Atipamezole (1.0 mg/kg) or 0.9% NaCl was administered on postoperative days 2 through 11 and 15, 19, and 23. Spontaneous behavior of rats in a transparent cylinder was videotaped before, and 6 and 23 days after surgery 20 min after drug administration. Constant asymmetry in forelimb use was observed in the cylinder test on postoperative days 6 and 23. Ischemic rats used the impaired forelimbs (contralateral to lesion) during lateral exploration less than did sham-operated rats (P<.001). Ischemic rats also preferred to turn contralateral to the lesion (P<.05). Atipamezole increased the simultaneous, but not independent, use of the forelimbs during lateral exploration (P<.05). The data suggest that noradrenergic manipulation does not significantly enhance recovery in a test that does not depend on practice following focal cerebral ischemia.