Short Term Effect of Mild Chronic Cerebral Hypoperfusion on Spatial Learning and Memory in Rats with/ without Electrical Stimulation

Abstract

The purpose of this study was to investigate the short-term effects of mild chronic cerebral hypoperfusion on spatial learning and memory in rats with or without electrical stimulation treatment. Male Sprague Dawley rats weighing 300 - 360g were randomly assigned into seven groups (n=8) of right common carotid artery occlusion (RCO), left common carotid artery occlusion (LCO), non-surgery (NS) and sham operated (sham) groups. Chronic cerebral hypoperfusion was induced by permanent ligation of either right or left common carotid artery. Electrical stimulation (stim) was delivered to the NS-stim, RCo-stim and LCO-stim groups for a period of 30 min, once a day from day 1 - 5 after arterial occlusion. Evaluations of spatial learning and memory were assessed in a Morris water maze at five days after arterial occlusion.
   Results revealed that five days of mild cerebral hypoperfusion induced either by permanent right or left common carotid occlusion had no effect on spatial leaning and memory when compared with the sham group. But when we compared the RCO and the LCO rats, we found that the RCO rats performed significantly better than the LCO rats on the second day of leaning; however; their performance tended to become persistently slower in the later phase than that of the LCO rats. Furthermore, the LCO rats tended to have better spatial memory than the RCO rats. Electrical stimulation therapy significantly enhanced spatial learning in NS and LCO rats but had no effect on the RCO rats.
   These findings may suggest that unilateral carotid occlusion may induce only short-term mild deficit in spatial learning in rats, and electrical stimulation treatment may help in improving mild cognitive impairment caused by cerebral hypoperfusion.