Pentobarbital produces activation and block of {alpha}1{beta}2{gamma}2S GABAA receptors in rapidly perfused whole cells and membrane patches: divergent results can be explained by pharmacokinetics.
Pentobarbital produces activation and block of {alpha}1{beta}2{gamma}2S GABAA receptors in rapidly perfused whole cells and membrane patches: divergent results can be explained by pharmacokinetics.
复制标题
DOI：
10.1085/jgp.200810081
复制
发表时间：
2009-02
影响因子：
3.8
通讯作者：
Roberts, William A.
中科院分区：
文献类型：
--
作者：
Gingrich, Kevin J.;Burkat, Paul M.;Roberts, William A.
毫摩尔浓度的巴比妥酸戊巴比妥(PB)激活γ-氨基丁酸(GABA)A型受体(GABA)，并在洗脱时引起矛盾电流增加或“尾巴”的阻断。为了探讨阻断的机制，我们采用快速灌流的方法，研究了重组α-1-β-2-γ-2S-GABA受体在全细胞和外向膜贴片上的PB触发电流。全细胞电流呈现典型的钟形浓度依赖关系，高浓度触发尾部电流，其峰值幅度与PB作用时相似。尾流时间过程在高浓度(≥3,000μM)下不能用多指数函数描述。随着PB浓度的增加和施加时间的延长，失活时间逐渐减慢。相比之下，大片尾电流表现出8倍的相对幅度，可用多指数函数描述，具有毫秒级的上升时间；失活发生在几秒内，对PB浓度和作用时间不敏感。建立了一个考虑宏块结果的简约门控模型(“面片”模型)。亲脂性药物分子通过细胞缓慢迁移，这是由于亲脂性隔膜进入亲脂性亚细胞室。在贴片模型中加入这样的药代动力学间隔，在细胞外交换时间过程中引入了一个缓慢的动力学成分，从而提供了对不同的整个细胞结果的概括。GABA联合应用可增强PB的阻断作用。总体而言，结果表明，PB浓度比激活时低6倍，涉及至少三个抑制性PB结合位点，表明在治疗性PB浓度下，被阻断的通道在GABA触发的活动中发挥作用，并提出了一个关于PB快速灌流全细胞的有效交换率的重要技术问题。
Millimolar concentrations of the barbiturate pentobarbital (PB) activate γ-aminobutyric acid (GABA) type A receptors (GABARs) and cause blockade reported by a paradoxical current increase or “tail” upon washout. To explore the mechanism of blockade, we investigated PB-triggered currents of recombinant α1β2γ2S GABARs in whole cells and outside-out membrane patches using rapid perfusion. Whole cell currents showed characteristic bell-shaped concentration dependence where high concentrations triggered tail currents with peak amplitudes similar to those during PB application. Tail current time courses could not be described by multi-exponential functions at high concentrations (≥3,000 μM). Deactivation time course decayed over seconds and was slowed by increasing PB concentration and application time. In contrast, macropatch tail currents manifested eightfold greater relative amplitude, were described by multi-exponential functions, and had millisecond rise times; deactivation occurred over fractions of seconds and was insensitive to PB concentration and application time. A parsimonious gating model was constructed that accounts for macropatch results (“patch” model). Lipophilic drug molecules migrate slowly through cells due to avid partitioning into lipophilic subcellular compartments. Inclusion of such a pharmacokinetic compartment into the patch model introduced a slow kinetic component in the extracellular exchange time course, thereby providing recapitulation of divergent whole cell results. GABA co-application potentiated PB blockade. Overall, the results indicate that block is produced by PB concentrations sixfold lower than for activation involving at least three inhibitory PB binding sites, suggest a role of blocked channels in GABA-triggered activity at therapeutic PB concentrations, and raise an important technical question regarding the effective rate of exchange during rapid perfusion of whole cells with PB.
登录
查看更多内容
影响因子：
4
作者：
AKAIKE, N;OOMURA, Y
通讯作者：
OOMURA, Y
影响因子：
3.6
作者：
Feng, HJ;Bianchi, MT;Macdonald, RL
通讯作者：
Macdonald, RL
影响因子：
16.2
作者：
JONES, MV;WESTBROOK, GL
通讯作者：
WESTBROOK, GL
影响因子：
5.5
作者：
BARKER, JL;RANSOM, BR
通讯作者：
RANSOM, BR
影响因子：
5
作者：
Dalziel, JE;Cox, GB;Birnir, B
通讯作者：
Birnir, B