The effect of MK-801 on the Na+, K+-ATPase activity and the free arachidonic acid level in hippocampus of ischemic rats

The influence of 20-min global cerebral ischemia on the Na+, K+-ATPase activity and free arachidonic acid (FAA)level in rat hippocampus at different time points after ischemia was examined. In addition, the effect of MK-801 on mentioned parameters was studied. Animals were exposed to 20-min global cerebral ischemia and were sacrified 0.5, 1, 2, 6, 24, 48, 72 and 168 hrs after ischemic procedure. The level of FAA and Na+, K+-ATPase activity was measured during all reperfusion periods mentioned above. Various doses of MK-801 (0.3 ; 1.0 ; 3.0 and 5.0 mg/kg) had been injected 30 min before ischemic procedure started. The rise in FAA level was found immediately after ischemia and during first 0.5 hr of reperfusion. The level of FAA increased again after 24 hrs and 168 hrs of recirculation. Treatment with 3.0 mg/kg of MK-801 significantly prevented the FAA accumulation immediately and 0.5 hr after ischemic insult while application with 5.0 mg/kg of MK-801 exerted protective effect during the first 24 hrs. Global cerebral ischemia induced the significant decline in the Na+, K+-ATPase activity in hippocampus starting from 1-168 hrs of reperfusion. Maximal inhibition was obtained 24 hrs after ischemic damage. Application of 3.0 mg/kg of MK-801 exerted statistically significant protective effects during first 24 hrs while the treatment with 5.0 mg/kg of MK-801 prevented fall in enzymatic activity during all reperfusion periods examined.