Amphetamine promotes task-dependent recovery following focal cortical ischaemic lesions in the rat

This study investigated the effect of amphetamine (AMP) on skilled forelimb use following focal cortical ischaemic lesions in the rat. Unilateral lesions were produced by a novel method of intracortical microinjection of endothelin-1 (ET-1), intended to principally target the forelimb representation zone in primary motor-primary somatosensory cortex. Lesions were placed in the hemisphere contralateral to the preferred limb and produced deficits in skilled forelimb use on two tasks: the paw reach (PR) test and the foot fault (FF) test. Beginning on post-lesion day (D) 2, animals received injections of 2 mg/kg AMP and were injected every third day until D26. Animals were tested both during, and 24 h after, AMP administration. AMP facilitated recovery of skilled forelimb use on the PR test when assessed during drug-free test sessions. No such effect was seen on the FF test. These results demonstrate that sub-acute administration of AMP following a unilateral focal ischaemic lesion of FL can facilitate task-dependent recovery of skilled forelimb use in the rat. They also demonstrate that different behavioural tasks measuring superficially similar behavioural outputs may show different sensitivities to such drug effects.