d-Amphetamine enhances skilled reaching after ischemic cortical lesions in rats

Unilateral sensorimotor cortical (SMC) lesions in rats impair reaching and grasping movements of the contralateral forelimb. These impairments can be improved using motor rehabilitative training on a skilled reaching task, but the training may be far from sufficient to return animals to pre-lesion levels of performance. Because d-amphetamine (AMPH) has been found to promote neuroplastic responses to injury and to be very beneficial when combined with some (but not all) types of rehabilitative training, we asked in this experiment whether it could improve the efficacy of rehabilitative training in skilled reaching. Ten to 14 days after unilateral ischemic (endothelin-1 induced) lesions of the SMC, adult rats were given a 3-week regimen of AMPH (1 mg/kg) coupled with daily rehabilitative training on a skilled reaching task, the single pellet retrieval task. AMPH treatment not only dramatically improved reaching performance compared with saline-injected controls, the AMPH treated rats surpassed pre-lesion levels of performance by the end of the rehabilitative training period. The greater performance in AMPH compared to saline-treated rats was still evident at 1 month, but not at 2 and 3 months, after the end of rehabilitative training. Thus, AMPH treatment can greatly enhance the efficacy of rehabilitative training on a skilled reaching task after unilateral SMC lesions, but alternate injection and training regimes may be needed to produce permanent improvements.