Locomotor hyperactivity and hippocampal CA1 injury after transient forebrain ischemia of gerbils

The influence of a repeated transient forebrain ischemia on the development of post-ischemic locomotor hyperactivity was determined in the gerbil. Animals were subjected to two episodes of 5 min bilateral carotid artery occlusion in halothane anesthesia separated by one week. By using an animal activity monitor for counting spontaneous movements, the locomotor activity was assessed before and after each ischemic period. Seven days after ischemia the number of intact hippocampal CA1 neurons was counted from histological sections. Following the first 5 min ischemia a phase of locomotor hyperactivity of more than 20-fold of control was observed. One week after ischemia less than 20% of CA1 neurons had survived. Exposure of gerbils at this time to a second 5 min ischemic episode did not cause any increased locomotor activity. These findings support the assumption that post-ischemic locomotor hyperactivity is a symptom of the acutely injured but still functionally active CA1 sector of hippocampus.