Mhatre M C, Ticku M K
Department of Pharmacology, University of Texas Health Science Center at San Antonio 78284-7764.
Brain Res Mol Brain Res. 1994 Jul;24(1-4):159-65. doi: 10.1016/0169-328x(94)90128-7.
Chronic GABA exposure of mammalian primary cultured cortical neurons results in a downregulation of the GABA-benzodiazepine receptor complex. In the present study, the mRNA levels, as well as polypeptide expression, for the GABAA receptor alpha 2 and alpha 3 subunits in cultured embryonic mouse cerebral cortical neurons (7 day old) were examined using northern analysis and immunoblotting techniques following chronic GABA treatment. The alpha 1 subunit mRNA or polypeptide could not be detected in these neurons. The steady state levels of mRNA for the GABAA receptor alpha 2 and alpha 3 subunits showed a decrease in comparison with untreated neurons. There was no change in the level of the beta actin or poly(A)+ RNA under the same experimental conditions. This agonist-induced reduction in the GABAA receptor alpha 2 and alpha 3 subunit mRNA was blocked by the concomitant exposure of neurons to R 5135, an antagonist of GABAA receptor. The polypeptide expression for the GABAA receptor alpha 2 and alpha 3 subunits in chronically GABA-treated neurons also showed a decline and this change was also blocked by the concomitant exposure of cells to GABA and R 5135. These results indicate that the chronic exposure of the GABAA receptor complex to agonist downregulates the expression of the alpha subunits of the receptor complex, which may be related to an observed decreases in the number of binding sites and GABA-induced 36Cl-influx in the cortical neurons.
对哺乳动物原代培养皮层神经元进行慢性γ-氨基丁酸（GABA）处理，会导致GABA-苯二氮䓬受体复合物下调。在本研究中，运用Northern印迹分析和免疫印迹技术，检测了慢性GABA处理后培养的胚胎小鼠大脑皮层神经元（7日龄）中GABAA受体α2和α3亚基的mRNA水平以及多肽表达。在这些神经元中未检测到α1亚基的mRNA或多肽。与未处理的神经元相比，GABAA受体α2和α3亚基的mRNA稳态水平有所降低。在相同实验条件下，β-肌动蛋白或聚腺苷酸（poly(A)+）RNA的水平没有变化。神经元同时暴露于GABAA受体拮抗剂R 5135可阻断这种由激动剂诱导的GABAA受体α2和α3亚基mRNA减少。在慢性GABA处理的神经元中，GABAA受体α2和α3亚基的多肽表达也出现下降，同时将细胞暴露于GABA和R 5135也可阻断这种变化。这些结果表明，GABAA受体复合物长期暴露于激动剂会下调该受体复合物α亚基的表达，这可能与观察到的皮层神经元中结合位点数量减少以及GABA诱导的36Cl内流减少有关。
