Temporal patterns of motor behavioural improvements by MK-801 in Mongolian gerbils submitted to different duration of global cerebral ischemia.

The purpose of this study was to investigate the temporal pattern of NMDA receptors antagonist-MK-801 on motor behaviour parameters in gerbils submitted to different duration of global cerebral ischemia. The common carotid arteries of gerbils were occluded for 5, 10 or 15min. Gerbils were given MK-801 (3mg/kg i.p.) or saline immediately after the occlusion in normothermic conditions prior to testing. Motor activity was registered 1, 2, 4, 7, 14, 21 and 28 days after reperfusion during 60min by open field test. At the same time, the effect of NMDA receptor blockade was followed in vivo by monitoring the neurological status of whole animals or at the cellular level by standard light and confocal microscopy on brain slices. Post-ischemic gerbils quickly developed hypermotor response with the most intensity in animals submitted to 15min ischemia. MK-801 administrated immediately after ischemia significantly decreased this hyperactivity. In all ischemic-treated animals, behavioural suppression by MK-801 was observed already 1 day after occlusion and was lasting as far as observed ischemia-dependent hypermotor responses. Beneficial effect of MK-801 was also confirmed by morphological and neurological status data. These findings suggest that sustained ischemia-induced hyperactivity is related to abnormalities in NMDA glutamatergic function, as well as its manifestation could be completely abolished by NMDA receptor blockade immediately after ischemic insult.