期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2012
卷号：109
期号：45
页码：18595-18600
DOI：10.1073/pnas.1204994109
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Benzodiazepines potentiate {gamma}-aminobutyric acid type A receptor (GABAAR) activity and are widely prescribed to treat anxiety, insomnia, and seizure disorders. Unfortunately, clinical use of benzodiazepines (BZs) is severely limited by tolerance. The mechanisms leading to BZ tolerance are unknown. BZs bind at the interface between an and {gamma} subunit of GABAARs, preferentially enhancing synaptic receptors largely composed of (1-3, 5), {beta}3, and {gamma}2 subunits. Using confocal imaging and patch-clamp approaches, we show that treatment with the BZ flurazepam decreases GABAAR surface levels and the efficacy of neuronal inhibition in hippocampal neurons. A dramatic decrease in surface and total levels of 2 subunit-containing GABAARs occurred within 24 h of flurazepam treatment, whereas GABAARs incorporating 1 subunits showed little alteration. The GABAAR surface depletion could be reversed by treatment with the BZ antagonist Ro 15-1788. Coincident with decreased GABAAR surface levels, flurazepam treatment reduced miniature inhibitory postsynaptic current amplitude, which returned to control levels with acute Ro 15-1788 treatment. GABAAR endocytosis and insertion rates were unchanged by flurazepam treatment. Treatment with leupeptin restored flurazepam lowered receptor surface levels, strongly suggesting that flurazepam increases lysosomal degradation of GABAARs. Together, these data suggest that flurazepam exposure enhances degradation of 2 subunit-containing GABAARs after their removal from the plasma membrane, leading to a reduction in inhibitory synapse size and number along with a decrease in the efficacy of synaptic inhibition. These reported subtype-specific changes in GABAAR trafficking provide significant mechanistic insight into the initial neuroadaptive responses occurring with BZ treatment.
