Direct evidence for diazepam modulation of GABA(A) receptor microscopic affinity

被引:104
作者
Lavoie, AM
Twyman, RE
机构
[1] UNIV UTAH,ECCLES INST HUMAN GENET,DEPT NEUROL,PROGRAM NEUROSCI,SALT LAKE CITY,UT 84112
[2] UNIV UTAH,DEPT NEUROL,PROGRAM HUMAN MOL BIOL & GENET,SALT LAKE CITY,UT 84112
[3] UNIV UTAH,DEPT PHARMACOL,SALT LAKE CITY,UT 84112
关键词
GABA(A) receptor; benzodiazepine; channel kinetics;
D O I
10.1016/S0028-3908(96)00077-9
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Alteration of agonist affinity is a potential mechanism for pharmacological modulation of ligand-gated receptor channel function. The time course for receptor activation and current onset is determined by the combined rates for two kinetic transitions that underlie the protein conformations for binding agonist and channel gating. Using ultrafast ligand exchange techniques, we distinguish between these previously difficult to separate events and demonstrate their independent pharmacological modulation. Diazepam, which increases apparent affinity of gamma-aminobutyric acid (GABA) to GABA(A) receptors, was used to examine its effects on GABA binding and ion channel gating of expressed alpha(2) beta(1) gamma(2) receptors from excised outside-out patches of acutely transfected HEK 293 cells. Diazepam increased rates of current onset evoked by low concentrations (<1 mM) but not at saturating GABA concentrations. Furthermore, rates of current decay were not affected during brief applications of GABA, and thus, demonstrated a diazepam specific effect on ligand binding affinity and not channel gating kinetics. However, current decay during and following prolonged GABA applications were altered by diazepam in a fashion similar to that for higher concentrations of GABA which also increased receptor desensitization. These findings and analysis by computer modeling indicated that diazepam likely enhances GABA receptor currents primarily by accelerating GABA association to its receptor at the first agonist binding site. These results provide the first direct physiological evidence for pharmacological modulation of microscopic binding affinity of GABA receptors. Copyright (C) 1996 Elsevier Science Ltd.
引用
收藏
页码:1383 / 1392
页数:10
相关论文
共 27 条
[11]  
LAURIE DJ, 1992, J NEUROSCI, V12, P4151
[12]   BARBITURATE REGULATION OF KINETIC-PROPERTIES OF THE GABAA RECEPTOR CHANNEL OF MOUSE SPINAL NEURONS IN CULTURE [J].
MACDONALD, RL ;
ROGERS, CJ ;
TWYMAN, RE .
JOURNAL OF PHYSIOLOGY-LONDON, 1989, 417 :483-500
[13]   HOW QUICKLY CAN GABA(A) RECEPTORS OPEN [J].
MACONOCHIE, DJ ;
ZEMPEL, JM ;
STEINBACH, JH .
NEURON, 1994, 12 (01) :61-71
[14]   KINETIC TIME CONSTANTS INDEPENDENT OF PREVIOUS SINGLE-CHANNEL ACTIVITY SUGGEST MARKOV GATING FOR A LARGE CONDUCTANCE CA-ACTIVATED K-CHANNEL [J].
MCMANUS, OB ;
MAGLEBY, KL .
JOURNAL OF GENERAL PHYSIOLOGY, 1989, 94 (06) :1037-1070
[15]   MODULATION OF DECAY KINETICS AND FREQUENCY OF GABA-A RECEPTOR-MEDIATED SPONTANEOUS INHIBITORY POSTSYNAPTIC CURRENTS IN HIPPOCAMPAL-NEURONS [J].
OTIS, TS ;
MODY, I .
NEUROSCIENCE, 1992, 49 (01) :13-32
[16]   TRANSIENT EXPRESSION SHOWS LIGAND GATING AND ALLOSTERIC POTENTIATION OF GABAA RECEPTOR SUBUNITS [J].
PRITCHETT, DB ;
SONTHEIMER, H ;
GORMAN, CM ;
KETTENMANN, H ;
SEEBURG, PH ;
SCHOFIELD, PR .
SCIENCE, 1988, 242 (4883) :1306-1308
[17]   TYPE-I AND TYPE-II GABAA-BENZODIAZEPINE RECEPTORS PRODUCED IN TRANSFECTED CELLS [J].
PRITCHETT, DB ;
LUDDENS, H ;
SEEBURG, PH .
SCIENCE, 1989, 245 (4924) :1389-1392
[18]   IMPORTANCE OF A NOVEL GABAA RECEPTOR SUBUNIT FOR BENZODIAZEPINE PHARMACOLOGY [J].
PRITCHETT, DB ;
SONTHEIMER, H ;
SHIVERS, BD ;
YMER, S ;
KETTENMANN, H ;
SCHOFIELD, PR ;
SEEBURG, PH .
NATURE, 1989, 338 (6216) :582-585
[19]  
PUIA G, 1991, MOL PHARMACOL, V39, P691
[20]   BENZODIAZEPINE AND BETA-CARBOLINE REGULATION OF SINGLE GABA(A) RECEPTOR CHANNELS OF MOUSE SPINAL NEURONS IN CULTURE [J].
ROGERS, CJ ;
TWYMAN, RE ;
MACDONALD, RL .
JOURNAL OF PHYSIOLOGY-LONDON, 1994, 475 (01) :69-82