Locomotor activity in the ischemic gerbil.

Previous studies have shown that within 24 h after ischemic insult, gerbils exhibit an increase in locomotor activity. Because activity gradually diminishes to normal levels with repeated testing, it has been argued that this behavior represents a reversible or transient effect of ischemia. The present study challenged this notion by testing ischemic gerbils at a time when increased activity is not observed with repeated testing. Ischemic (5-min bilateral carotid occlusion) and sham gerbils were tested for 14 consecutive days after reperfusion in an open-field apparatus (n = 6/condition). As previously reported, ischemic gerbils exhibited a significant increase in activity (days 1 and 2) which returned to control levels with repeated testing (days 13 and 14). A second group of ischemic and sham gerbils (n = 6/condition) were tested only on days 13 and 14 after reperfusion. In contrast to those tested repeatedly, these ischemic gerbils displayed increased locomotor activity as compared with sham controls. In addition, gerbils in the repeated testing conditions were evaluated in a semi-novel testing environment on days 15 and 16 after surgery. The locomotor activity of ischemic gerbils significantly increased in response to the semi-novel environment. These results suggest that the effects of ischemia on locomotor activity are not limited to a brief period after occlusion and may represent a permanent deficit. In addition, as previously suggested, this behavior may represent a deficit in habituation or spatial mapping rather than motor hyperactivity.