Unilateral lesions of the forelimb area of rat motor cortex: lack of evidence for use-dependent neural growth in the undamaged hemisphere.

Unilateral lesions of the forelimb area of the motor cortex have been reported to produce enhanced dendritic outgrowth in the undamaged hemisphere in response to the behavioral asymmetry produced by the lesions (e.g. Jones, T.A. and Schallert, T., Use-dependent growth of pyramidal neurons after neocortical damage, J. Neurosci, 14 (1994) 2140-2152). We attempted to replicate this result and to determine if there were sex differences in cortical plasticity using the Jones and Schallert model. Animals were given either unilateral aspiration or electrolytic lesions of the forelimb area of the motor cortex or a sham operation. Use of the forelimb ipsilateral to the lesion for postural support was assessed pre- and postsurgery. Eighteen days after surgery the animals were sacrificed. and the brains processed for Golgi-Cox staining or a series of other stains for acetylcholine, astrocytes (glial fibrillary acidic protein), and microglia (OX-42). Although the lesions produced significant behavioral asymmetry and enhanced glial response on the lesioned side, there was little evidence for use-dependent neural growth in the undamaged hemisphere in either sex.