GRAFT-INDUCED RECOVERY OF INHIBITORY AVOIDANCE-CONDITIONING IN STRIATAL LESIONED RATS IS RELATED TO CHOLINE-ACETYLTRANSFERASE ACTIVITY

Four groups of male Wistar rats showing disrupted inhibitory avoidance conditioning due to striatal lesions received either striatal or vent ral mesencephalic brain grafts. Two additional non-lesioned groups wer e used as controls. Half of the groups was retrained in an inhibitory avoidance task at fifteen days postgraft and the other half at sixty d ays postgraft. Those animals receiving striatal grafts significantly i mproved their ability to acquire the inhibitory avoidance task at fift een and sixty days postgraft, as opposed to those receiving mesencepha lic grafts, which did not show behavioral recovery. Choline acetyltran sferase and glutamate decarboxylase activities, as well as dopamine co ntent, were measured in the grafted tissue. Striatal grafts showed lev els of choline acetyltransferase activity similar to the control group . Moreover, a positive correlation was found between the choline acety ltransferase activity and the behavioral recovery. In contrast, both g lutamate decarboxylase activity and dopamine levels were significantly lower in striatal and in mesencephalic grafts, as compared to the con trols. These results show that striatal but not mesencephalic grafts c an promote the restoration of the ability to acquire an inhibitory avo idance task even at early stages (15 days) of the development of the g rafts. The results also suggest that acetylcholine plays an important role in behavioral recovery.