乙醇对小鼠不同脑区^3H—GABA与GABAA受体结合的影响

EFFECTS OF ETHANOL ON 3 H GABA BINDING WITH GABA A RECEPTOR IN DIFFERENT AREAS OF BRAIN IN MICE

采用放射配体受体结合分析法，研究急性注射乙醇对小鼠不同脑区ＧＡＢＡＡ受体饱和曲线以及与＾３Ｈ－ＧＡＢＡ结合的影响。结果表明，急性注射乙醇３０ｍｉｎ后，ＧＡＢＡＡ受体饱和曲线出现大幅度上移，乙醇能明显提高＾３Ｈ－ＧＡＢＡ与ＧＡＢＡＡ受体的结合，对小脑、下丘脑、海马及大脑皮层分别提高２０％、１６％、３０％和２８％。乙醇能逆转ＧＡＢＡＡ受体拮抗剂如印防己毒素（Ｐｉｃｒｏ－ｔｏｘｉｎ）。

GABA is the major inhibitory neurotransmitter in the mammalian central nervous system(CNS),and the GABA A receptor is a member of a gene superfamily of ligand gated ion channel,which shows differential sensitivity to pharmacological manipulation by effects such as ethanol.The toxic effects of ethanol on CNS have been stuied for several decades,but the mechanism of the ethanol action on CNS is still not known.The understanding of the effect of ethanol on CNS is essential for the exploration of the cause of alcoholism.This paper is focused on the relation between the effects of ethanol and the activity of GABA ergic system in the different regions of brain in mice. The effects of acute injection of ethanol on the saturation curves of GABA A receptor and 3 H GABA binding in different areas of brain in mice were studied by using radioligand receptor binding assay.30 minutes after injection of ethanol(20μL/g, body weight),different drugs (Picrotoxin, Bicuculline, Barbiturate, Muscimol, Aminooxyacetic acid and Baclofen)were given by i.p.or i.c.v.to the mice.High speed centrifugation was used to prepare GABA receptors from cerebellum,hypothalamus,hippocampus and cerebral cortex(lobus frontalis).The saturation curves of GABA A receptor binding were measured by using liquid scintillation counter(Packard 2200) with various concentration of 3 H GABA (4nmol/L～150nmol/L).The specific binding of 3 H GABA was calculated by subtracting the nonspecific binding the dpm from the total value of dpm,and the number of GABA A receptors was calculated.The concentration of receptor protein was measured by a modified method of Lowry.The datas were analyzed by t test. The results showed that after 30 minutes of the ethanol acute injection,the saturation binding of 3 H GABA increased significantly,the binding of 3 H GABA to GABA A receptor reached to 20%,16%,30% and 28% for cerebellum,hypothalamus,hippocampus and cerebral cortex respectively.The results also showed that the inhibitory effect of GABA A receptor antagonist Picrotoxin and Bicuculline to CNS was abolished by ethanol injection on the one hand. On the other hand,ethanol enhanced the binding of Barbiturate, Muscimol, Aminooxyacetic acid to GABA A receptor in various rate.Baclofen decreass the level of binding to GABA A receptor. In conclusion,ethanol may have an inhibitory effect on central nervous system by increasing the binding of 3 H GABA to GABA A receptor in brain.