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Activation and block of recombinant GABA(A) receptors by pentobarbitone: a single-channel study.
Akk, G; Steinbach, J H.
Afiliación
  • Akk G; Department of Anesthesiology, Washington University School of Medicine, St Louis, Missouri, MO 63110, USA. akk@morpheus.wustl.edu
Br J Pharmacol ; 130(2): 249-58, 2000 May.
Article en En | MEDLINE | ID: mdl-10807661
ABSTRACT
Recombinant GABA(A) receptors (alpha1beta2gamma2L) 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. Clusters of single-channel activity elicited by 500 microM 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 approximately 1500 s(-1), and the estimated equilibrium dissociation constants for the binding steps involved in activation are approximately 2 mM. 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. 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. 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.
Asunto(s)

Texto completo: 1 Banco de datos: MEDLINE Asunto principal: Fenobarbital / Receptores de GABA-A / Anticonvulsivantes Límite: Animals / Humans Idioma: En Revista: Br J Pharmacol Año: 2000 Tipo del documento: Article País de afiliación: Estados Unidos

Texto completo: 1 Banco de datos: MEDLINE Asunto principal: Fenobarbital / Receptores de GABA-A / Anticonvulsivantes Límite: Animals / Humans Idioma: En Revista: Br J Pharmacol Año: 2000 Tipo del documento: Article País de afiliación: Estados Unidos