急性重复缺氧对小鼠脑组织腺苷及其 A_1 受体的影响

EFFECTS OF ACUTE REPEATED HYPOXIA ON LEVELS OF ADENOSINE AND ITS A 1 RECEPTOR IN MOUSE BRAIN

分别应用酶鉴别分光光度法和放射性配体结合法测定小鼠脑组织腺苷（ａｄｅｎｏｓｉｎｅ，ＡＤＯ）含量及Ａ１受体在急性重复缺氧过程中的变化。发现经急性重复缺氧处理的动物全脑内ＡＤＯ含量有一定程度的累积增加，尤其在海马、脑桥和延髓处的增加较为显著；各脑区Ａ１受体的数目显著低于正常对照组，但海马、脑桥和延髓处Ａ１受体的亲和力显著高于正常对照组。结果提示，重复缺氧后虽然脑内Ａ１受体数目减少，但由于海马、脑桥和延髓处Ａ１受体的亲和力升高，累积增加的ＡＤＯ和Ａ１受体结合后，抑制神经细胞兴奋性的作用仍可能得到加强，从而使ＡＤＯ仍能更好地发挥抑制性神经调制作用。

Experiments were conducted on Kunming mice. Content of adenosine(ADO) and its metabolites in the brain was measured by specific enzymatic method, and radioligand binding method was used to study ADO A 1 receptor. ADO content of the hippocampus in group C(hypoxia exposure for four runs) was markedly higher than that in groups A(control, without hypoxia exposure) and B(hypoxia exposure for one run), showing that ADO content can be cumulatively increased in the hippocampus, which is more sensitive to ischemia and hypoxia, during acute repeated hypoxia exposures. A 1 receptor density, but of group C was significantly lower than that of group A and no difference was seen between groups B and C, but A 1 receptor affinity in the hippocampus, pons and medula oblongata in group C was significantly higher than that in group A, implying that during acute repeated hypoxia there may be some mechanisms preventing A 1 receptor density from decreasing further and making A 1 receptor affinity increase in some brain regions. These results indicate that cumulatively increased ADO in the hippocampus via A 1 receptor may play a neuroprotective role in CNS as an inhibitory neuromodulator and thus contribute to the formation and development of acute hypoxia adaptation or tolerancee.