Chronic low-dose administration of nicotine facilitates recovery and synaptic change after focal ischemia in rats

The current study examines the effects of chronic administration of nicotine on motor behavior after focal stroke in rats. Animals were trained in a tray-reaching task for 2 weeks and then they were divided into: (1) control + saline (2) control + nicotine (3) stroke + saline, and (4) stroke + nicotine groups. Lesions were produced by devascularization of the surface blood vessels of the sensorimotor cortex contralateral to the forepaw used for reaching. Forty-eight hours after the lesions, and for a total of 12 days, animals received two daily injections of either nicotine (0.3 mg/kg) or saline (0.9%). Animals were tested in a motor battery I week after the lesions and every other week for a total of 7 weeks. Pyramidal cells in forelimb and cingulate areas were then examined for dendritic length and branching using a Golgi-Cox procedure. Behavioral results demonstrated that by the end of the testing stroke + nicotine animals showed significant behavioral improvement relative to stroke + saline animals. Stroke + nicotine animals showed an increase in dendritic length and branching in pyramidal cells of the forelimb and cingulate areas. The results suggest that the behavioral enhancement in the stroke + nicotine group might be attributable to the enhanced dendritic growth in residual cortical motor regions. (c) 2005 Elsevier Ltd. All rights reserved.