CHANGES IN LOCOMOTOR-ACTIVITY AND PASSIVE-AVOIDANCE TASK-PERFORMANCE INDUCED BY CEREBRAL-ISCHEMIA IN MONGOLIAN GERBILS

Background and Purpose We investigated changes in locomotor activity, passive avoidance task performance, and hippocampal CA1 neurons induced by cerebral ischemia in Mongolian gerbils to examine the relation between these behavioral changes and CA1 neuronal damage. Methods Spontaneous locomotor activity was measured using the open field method before and 1, 3, 7, 14, or 28 days after 1- to 5-minute occlusion of the bilateral common carotid arteries. Locomotor activity after the second episode of 5-minute ischemia was also measured at 1-month intervals. The passive avoidance task was performed 7 or 28 days after induced ischemia. Histopathological changes in CA1 neurons after ischemia were assessed. Results Locomotor activity was increased 1 and 3 days after induced ischemia but not 14 and 28 days later. When the gerbils were again subjected to 5-minute ischemia 1 month after the initial 5-minute induced ischemia, locomotor activity even I day later was significantly increased. In contrast, passive avoidance impairment depended on the duration of ischemia, as determined 7 and 28 days after induced ischemia. Hippocampal CA1 neuronal damage was progressive, that is, changes in CA1 neurons were apparent even 1 day after 5 minutes of induced ischemia, and the CA1 neurons disappeared 7 days after 5 minutes of ischemia. Conclusions Passive avoidance impairment after ischemia is related to damage of CA1 neurons. Changes in locomotor activity after induced ischemia do not seem to be linked to CA1 neuronal damage.