Cognitive deficits after focal cerebral ischemia in mice.

BACKGROUND AND PURPOSE The interpretation of cognitive data in many experimental stroke studies is problematic because middle cerebral artery occlusion (MCAO) is associated with sensorimotor alterations that may become confounding factors in cognitive testing. The purpose of the current study was to determine if it is possible to measure MCAO-induced cognitive deficits by using short durations of ischemia that do not result in alterations in sensorimotor behavior in mice. METHODS Male C57/Bl6 mice were subjected to 60 or 90 minutes of intraluminal MCAO or sham surgery. In the first cohort of animals (n=12/group), locomotor activity, balance, and coordination were evaluated 2 weeks after surgery. In a second cohort of animals (n=10/group), the effects of 60 minutes of MCAO on subsequent learning and memory were assessed with a step-down passive avoidance task beginning 1 week after surgery. In a third cohort of animals (n=8 to 10/group), training in a passive avoidance task was completed before 60 minutes of MCAO, then retention of the task was assessed 1 week after surgery. In all animals, infarction size was determined after 14 days of reperfusion with use of cresyl violet staining and quantitative image analysis. RESULTS There was no significant difference in infarction volume in the cerebral cortex or caudoputamen after 60 versus 90 minutes of MCAO. However, there was a significant increase in latency to move 1 body length in the 90-minute MCAO group compared with the 60-minute MCAO and sham groups. In 2 additional cohorts of animals, 60-minute MCAO was associated with a deficit in the acquisition and retention of a passive avoidance task regardless of whether the task training occurred before or after MCAO. CONCLUSIONS Long-term cognitive deficits can be induced in mice by using a short duration of MCAO (60 minutes) that does not result in concomitant sensorimotor deficits.