CHRONIC BENZODIAZEPINE EFFECTS ON GABA RECEPTOR COMPLEX

对苯二氮卓类（BZ）作用的耐受性，特别是 它们的抗惊厥作用限制了它们的临床用途。 容忍 发展可能也是决定慢性疾病模式的一个因素。 虐待 BZ作用于GABA上的调节位点受体 受体增加GABA介导的Cl-通量。 各种管制 GABA/BZ/Cl-通道复合物上的结合位点与 宽容，但研究结果不一致。 使用标准 慢性BZ治疗，对BZ局部注射的行为不敏感， 和GABA激动剂在黑质网状部（SNpr）显示， 不同的耐受性发展和逆转的时间进程表明 涉及GABA复合物调节的多种机制可能介导 BZ神经元敏感性的改变。 受体放射自显影显示 BZ和GABA激动剂敏感性与慢性BZ治疗是一个函数， GABA复合物的修饰。 海马体是大脑 唯一适合测试这一点和相关的假设。 的局部变化 BZ和GABA激动剂敏感性将使用细胞外 电生理学方法使用GABA能抑制电路， 海马结构作为基底。 结合的相关修饰 GABA/BZ/Cl-通道复合物上的位点和位点-位点相互作用将被 在5个组织学鉴定的椎板中平行系统研究 海马的放射自显影结合方法。 的影响 慢性BZ治疗将在几个时间点进行评价， 停止1或4周的氟安定（FZP）治疗。 离体海马脑片电生理测量 通过（A）评估BZ和GABA效力和功效的变化 使用“成对脉冲”的内源性GABA能系统的功能 原型BZ的抑制和（B）浓度效应研究 （地西泮、FZP、脱烷基FZP和氯硝西泮）和GABA激动剂（GABA， 蝇蕈醇、THIP和异胍辛）。 放射自显影测量将 由（A）GABA（[3 H]蝇蕈醇和[3 H]荷包牡丹碱）、BZ（[3 H] Ro 15 -1788）、 和Cl-通道（[35 S]叔丁基双环硫代磷酸盐，TBPS）结合，以及（B） GABA/BZ（[3 H]氟硝西泮+ GABA）和GABA/Cl-通道（[35 S]TBPS + GABA） 偶合器. 这项工作将提供进一步的信息， GABA/BZ/Cl-通道在神经元长期适应中的相互作用 这发生在长期使用BZ的人身上。

Development of tolerance to benzodiazepine (BZ) effects, in particular their anticonvulsant actions, limits their clinical usefulness. Tolerance development is probably also a factor in determining patterns of chronic abuse. BZs act at receptors which are modulatory sites on the GABA receptor to increase GABA-mediated Cl- flux. Regulation of the various binding sites on the GABA/BZ/Cl- channel complex has been implicated in tolerance, yet results of studies are inconsistent. Using a standard chronic BZ treatment, behavioral subsensitivity to local injection of BZ and GABA agonists in substantia nigra pars reticulata (SNpr) showed different time-courses of tolerance development and reversal suggesting multiple mechanisms involving regulation of the GABA complex might mediate alterations in BZ neuronal sensitivity. Receptor autoradiography revealed BZ and GABA agonist sensitivity with chronic BZ treatment are a function of modifications at the GABA complex. The hippocampus is the brain site uniquely suited to test this and associated hypotheses. Local changes in BZ and GABA agonist sensitivity will be sought using extracellular electrophysiological methods using the GABAergic inhibitory circuits in hippocampal formation as a substrate. Associated modification of binding sites and site-site interactions on the GABA/BZ/Cl- channel complex will be systematically studied in parallel in 5 histologically identified laminae of hippocampus using autoradiographic binding methods. The effect of chronic BZ treatment will be evaluated at several time-points after discontinuing a 1 or 4 week flurazepam (FZP) treatment. Electrophysiological measurements in in vitro hippocampal slice will evaluate changes in BZ and GABA potency and efficacy by (A) evaluating the function of the endogenous GABAergic system using "paired-pulse" inhibition, and (B) concentration effect studies of prototype BZs (diazepam, FZP, desalkylFZP and clonazepam) and GABA agonists (GABA, muscimol, THIP and isoguavacine). Autoradiographic measurements will be made of (A) GABA ([3H]muscimol and [3H]bicuculline), BZ ([3H]Ro15-1788), and Cl- channel ([35S]t-butylbicyclophosphothionate, TBPS) binding, and (B) GABA/BZ ([3H]flunitrazepam + GABA) and GABA/Cl- channel ([35S]TBPS + GABA) coupling. This work will provide further information about the nature of GABA/BZ/Cl- channel interactions in the long-term neuronal adaptations which occur to BZs with chronic use.