CHRONIC BENZODIAZEPINE EFFECTS ON GABA RECEPTOR COMPLEX

尤其是对苯二氮卓类(BZ)的耐受性的发展 它们的抗惊厥作用限制了它们的临床应用。容差 发展可能也是决定慢性病模式的一个因素。 虐待。BZS作用于受体，而受体是GABA的调节部位 受体可增加GABA介导的氯离子通量。监管各种不同的 GABA/BZ/Cl-通道复合体上的结合位点与 然而，研究结果并不一致。使用标准 慢性BZ治疗，局部注射BZ的行为亚敏感 和GABA激动剂在黑质网状部(SNPR)显示 不同时间段的耐受性发展和逆转提示 涉及调节GABA复合体的多种机制可能在 BZ神经元敏感性的改变。受体放射自显影显示 BZ和GABA激动剂对慢性BZ治疗的敏感性是 GABA复合体的修饰。海马体是大脑的位置 独一无二地适合检验这一假说和相关假说。中的本地更改 将使用细胞外方法寻找BZ和GABA激动剂的敏感性 使用GABA能抑制电路的电生理学方法 以海马体结构为底物。绑定的关联修改 GABA/BZ/Cl-通道复合体上的位点和位点间的相互作用将是 对5个组织学鉴定的椎板进行系统平行研究 用放射自显影结合的方法对海马区进行定位。的影响 慢性BZ治疗将在以下几个时间点进行评估 停用1周或4周的氟安定(FZP)治疗。 离体海马脑片的电生理测量 通过(A)评估BZ和GABA的效力和疗效的变化 利用“双脉冲”实现内源性GABA能系统的功能 (B)原形BZS的浓度效应研究 (地西潘、FZP、去烷基FZP和氯硝西潘)和GABA激动剂(GABA， 麝香酚、THIP和异愈创木酚)。放射自显影测量将是 由(A)GABA([~3H]蝇草酚和[~3H]荷包牡丹碱)，BZ([~H]Ro15-1788)， 和氯通道([35S]叔丁基双环硫代磷酸，Tbps)结合，和(B) GABA/BZ([~3H]氟硝西潘+GABA)和GABA/Cl-通道([35S]Tbps+GABA) 耦合。这项工作将提供有关性质的进一步信息 神经元长期适应中的GABA/BZ/Cl-通道相互作用 对于长期使用的BZS来说，这些都是可能的。

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.