Effect of hyperbaric oxygen on the alteration of N-methal-D-aspartate in gerbils hippocampus following cerebral ischemia and reperfusion

Objective To study the effect of hyperbaric oxygen(HBO) on the biological property of N-methal-D-aspartate (NMDA) receptor inhibitor in gerbils hippocampus following cerebral ischemia and reperfusion. Methods Mongolian gerbils were used to develop the model of hemorrhage of forebrain by ligation of bilateral arteria carotis communis. The animals were randomly divided into the sham surgery group, the isehemia and reperfusion group, the HBO group, the ketamine group and the ketamine plus HBO group. Radioligand ([3H]-CPP) was employed to define equilibrium binding characteristics of the NMDA receptor in hippocampus. Maximal binding (Bmax) and affinity constant (Kd) of NMDA receptors were determined. Results Changes in affinity constant (Kd) could be seen in all the groups following ischemia, but without statistical significance. Significant changes in Bmax were shown following ischemia and there was statistical importance, when a comparison was made between the ischemia and reperfusion group and the sham surgery group (P<0.01). Following 30 minutes of ischemia, NMDA receptor maximal binding(Bmax) of the other groups decreased more significantly than that of the ischemia-reperfusion group (P<0.01). Of all the groups, Bmax of the ketamine group and the ketamine plus HBO group dropped more significantly. Conclusions Results indicated that Bmax of [3H]-CPP increased markedly after 30 minutes of cerebral ischemia in gerbils hippocampus. Both ketamine and ketamine plus HBO treatment could decrease the level of Bmax, which might reduce entry of Ca2+ into cells during ischemia and reperfusion, and at the same time, restore concentration of intracellular calcium [Ca2+]. All this might account for the therapeutic effect of HBO on cerebral ischemia. Key words: Hyperbaric oxygen ;  Cerebral ischemia;  N-methal-D-aspartate;  Hippocampus