PT - JOURNAL ARTICLE AU - Mohammad H. Jalilian Tehrani AU - Eugene M. Barnes, Jr. TI - Sequestration of γ-Aminobutyric Acid<sub>A</sub> Receptors on Clathrin-Coated Vesicles During Chronic Benzodiazepine Administration <em>In Vivo</em> DP - 1997 Oct 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 384--390 VI - 283 IP - 1 4099 - http://jpet.aspetjournals.org/content/283/1/384.short 4100 - http://jpet.aspetjournals.org/content/283/1/384.full SO - J Pharmacol Exp Ther1997 Oct 01; 283 AB - Chronic administration of benzodiazepine agonists produces behavioral tolerance. For induction of tolerance, the use-dependent down-regulation of γ-aminobutyric acidA(GABAA)/benzodiazepine receptors is a potential cellular mechanism. We previously identified GABAA receptors on clathrin-coated vesicles from rat brain, suggesting that surface receptors can be internalized via endocytosis. To examine a role for coated vesicles in GABAA receptor down-regulation in vivo, fractions were obtained from mouse brain microsomes through density centrifugation and treatment with 0.1% Triton X-100. This coated vesicle preparation was enriched in clathrin subunits and clathrin light-chain kinase and had twice the level of [3H]flunitrazepam binding as did vesicles not exposed to Triton. Adult mice were treated with lorazepam (2 mg/kg/day) for 7 days via osmotic minipump, achieving a serum level of 103 ± 8.9 ng/ml. The level of flunitrazepam bound to coated vesicles was increased by 83 ± 13% in the lorazepam-treated mice compared with vehicle-treated controls. TheBmax value for [3H]flunitrazepam binding to synaptic membranes from lorazepam-treated animals was 33 ± 4% lower than that of controls. The amount of GABAA receptor alpha-1 subunits, as quantified by Western blotting, followed a similar pattern. Relative to controls, immunoreactivity for alpha-1 subunits in coated vesicles from lorazepam-treated mice was increased by 60.0 ± 10.3%, whereas that in synaptic membranes declined by 12 ± 6%. These results indicate that lorazepam-dependent GABAA receptor sequestration occurs in mouse brain. Furthermore, it is suggested that this sequestration may play a role in GABAA receptor down-regulation in vivo. The American Society for Pharmacology and Experimental Therapeutics