Differential recovery of inhibitory avoidance learning by striatal, cortical, and mesencephalic fetal grafts.

Four groups of male Wistar rats showing disrupted inhibitory avoidance conditioning due to striatal lesions were studied. Three groups received striatal, cortical, or ventral mesencephalic brain grafts and the fourth group remained as a lesioned control. Sixty days postgraft the animals were retrained in an inhibitory avoidance task. The striatal-grafted animals were the only group that significantly improved in the ability to acquire the inhibitory avoidance task. Acetylcholinesterase histochemistry revealed positive patches of cells in the striatal grafts. Cortical grafts showed less reactivity, without patches. Immunocytochemical analyses for tyrosine hydroxylase revealed positive cell reactivity in the mesencephalic grafts and few positive fibers were detected in the border between the striatal grafts and the host tissue. These results demonstrate that striatal but not cortical or mesencephalic brain grafts can promote the restoration of the ability to acquire an inhibitory avoidance task and suggest that the acetylcholine tissue content is involved in the behavioral recovery.