Activation and block of recombinant GABAA receptors by pentobarbitone:: a single-channel study
Activation and block of recombinant GABAA receptors by pentobarbitone:: a single-channel study
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DOI：
10.1038/sj.bjp.0703335
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发表时间：
2000-05-01
影响因子：
7.3
通讯作者：
Steinbach, JH
中科院分区：
文献类型：
--
作者：
Akk, G;Steinbach, JH
1 Recombinant GABAA receptors (alpha 1 beta 2 gamma 2L) were transiently expressed in HEK 293 cells. We have investigated activation and block of these receptors by pentobarbitone (PB) using cell-attached single-channel patch clamp.2 Clusters of single-channel activity elicited by 500 mu M PB were analysed to estimate rate constants for agonist binding and channel gating. The minimal model able to describe the kinetic data involved two sequential binding steps, followed by channel opening. The estimated channel opening rate constant is similar to 1500 s(-1), and the estimated equilibrium dissociation constants for the binding steps involved in activation are similar to 2 mM.3 Our results show a dose-dependent block of receptors at millimolar concentrations of PB that results in reduced open interval durations. The reduction in mean open time is linearly proportional to PB concentration, indicating that block can be produced by binding of a single PB molecule.4 Addition of millimolar concentrations of PB in the presence of GABA also produces a reduction of open channel lifetime in addition to a progressive increase in the closed interval durations within a cluster. The data suggest that the receptor contains two or more blocking sites while occupancy of only one of the sites is sufficient for channel block.5 Neither the blocking rate constant nor return rate from the blocked state(s) is affected by pH (ionization status of the PB molecule) demonstrating that both neutral and anionic forms of PB cause channel block.
