Unilateral ischemic sensorimotor cortical damage in female rats: forelimb behavioral effects and dendritic structural plasticity in the contralateral homotopic cortex

Abstract

Previous studies in male rats with unilateral sensorimotor cortical (SMC) damage have demonstrated dendritic structural plasticity in the contralateral homotopic cortex and an enhancement of skilled reaching performance in the forelimb ipsilateral to the lesion compared to sham-operated rats. The purpose of this study was to determine if these findings could be replicated in an ischemic lesion model in female rats. Female rats were given sham operations or unilateral ischemic (endothelin-1 induced) damage in the forelimb representation area of the SMC opposite their preferred forelimb. Animals then received either 20 consecutive days of training on a skilled reaching task with the non-preferred/unimpaired forelimb or no-training control procedures. The surface density of dendrites immunoreactive (IR) for microtubule-associated protein 2 (MAP2) was then measured in the motor cortex opposite the trained limb and/or lesion. Female rats with sufficiently large, but not very small, lesions performed better with the unimpaired forelimb than sham-operated rats on the reaching task. The post-lesion reaching performance was not found to be significantly dependent upon estrous stage at the time of surgery, in agreement with previous studies that failed to find sex or sex-hormone effects after other types of SMC damage. Additionally, there were major laminar-dependent increases in the surface density of MAP2 IR dendrites in the cortex opposite lesions and trained limbs. These findings in female rats are consistent with the dendritic and behavioral changes previously found in male rats. They extend these previous findings by indicating that lesion size is an important variable in the enhancement of reaching performance.