EFFECTS OF DORSAL NORADRENERGIC BUNDLE LESIONS ON RECOVERY AFTER SENSORIMOTOR CORTEX INJURY

Several lines of evidence suggest that the recovery of the ability of rats to traverse a narrow beam after unilateral injury to the sensorim otor cortex is noradrenergically mediated. We tested the hypotheses th at the influence of norepinephrine on beam-walking recovery occurs, at least partially, through effects in the contralateral and/or ipsilate ral cerebral cortex. Rats had either a selective left or right B-hydro xydopamine lesion or sham lesion of the dorsal noradrenergic bundle (D NB) 2 weeks before suction-ablation or sham injury of the right sensor imotor cortex. The rats' abilities to perform the beam-walking task we re measured over the 10 days following cortex surgery. DNB lesions did not affect the initial severity of the beam-walking deficit and had n o effect on the performance of the task in rats with sham cortex injur ies. Lesions of the contralateral but not ipsilateral DNB significantl y impaired recovery. Further, in cortically lesioned rats with contral ateral DNB lesions, norepinephrine content in the cerebral cortex oppo site to the sensorimotor cortex lesion was significantly correlated wi th recovery. These data suggest that the effect of norepinephrine on r ecovery of beam-walking ability may be partially exerted in the cerebr al cortex contralateral to the injury. (C) 1997 Elsevier Science Inc.