Relationship between dendritic pruning and behavioral recovery following sensorimotor cortex lesions

A unilateral injury to the forelimb area of the sensorimotor cortex results in an increase in dendritic arborization in the contralateral homotopic co rtex which is followed by a pruning back of these dendritic arbors. The inc rease in arborization is due to an increase in the use of the unimpaired fo relimb for postural-motor support, whereas, the dendritic pruning is relate d, in time, to the return to more symmetrical limb use, but is not prevente d by the maintenance of asymmetrical limb use. Dendritic pruning can be pre vented by administering an NMDA receptor antagonist (such as MK801 or ethan ol) during the pruning phase. This manipulation also coincides with the chr onic reinstatement of behavioral deficits. The purpose of this study was to see whether removing the antagonism of the NMDA receptor results in the ev entual return of dendritic pruning and behavioral recovery. Therefore, MK80 1 was administered to lesioned animals starting at post-lesion day 18. One group received MK801 injections until day 60 (Lesion + MK60) and another le sioned group received MK801 until day 30 after which the injections were ch anged to saline until day 60 (Lesion + ME;30). Lesion + MK60 animals showed a prevention of dendritic pruning as well as a chronic reinstatement of fo relimb deficits. Lesion + MK30 animals also showed a prevention of dendriti c pruning, however, they showed behavioral recovery. These findings suggest that pruning of dendritic arbors may not be directly related to behavioral recovery. (C) 1998 Elsevier Science B.V. All rights reserved.