LONG-TERM SPATIAL COGNITIVE IMPAIRMENT FOLLOWING MIDDLE CEREBRAL-ARTERY OCCLUSION IN RATS - A BEHAVIORAL-STUDY

Behavioral changes in the chronic phase of permanent occlusion of the right middle cerebral artery (MCA) in rats were investigated. One mont h after MCA occlusion, 23 rats were unable and 7 rats were able to sol ve a radial 8-arm maze task during a 1-month period. Three months afte r occlusion, 19 MCA-occluded rats failed to solve the task successfull y again during at least a 1-month period (the cognitively impaired rat s), and 11 MCA-occluded rats were able to solve it (the cognitively un impaired rats). When a delay of 60 min was imposed for this task, five cognitively unimpaired rats failed to solve it. The locomotor activit y of the cognitively impaired rats increased significantly 2 months af ter occlusion, and this increase showed good correlation with spatial cognitive deficit. However, the mean time a rat spent at each arm rema ined unchanged among the cognitively impaired, unimpaired, and sham-op erated rats. There was no significant difference in the ratio between the cognitively impaired and unimpaired rats for disturbed motor coord ination. These results suggest that MCA occlusion is capable of produc ing long-term spatial cognitive disturbance in rats. In addition, this spatial cognitive deficit does not seem to be primarily due to hyperm otility or a disturbance in motor coordination.