Kraushaar Udo, Backus Kurt H
Institute of Physiology, University of Freiburg, Hermann-Herder-Strasse 7, 79104 Freiburg, Germany.
Pflugers Arch. 2002 Nov;445(2):279-88. doi: 10.1007/s00424-002-0924-8. Epub 2002 Sep 13.
GABA(A) receptors (GABA(A)Rs) and glycine receptors (GlyRs) expressed in developing neurons (P3-8) of the rat inferior colliculus (IC) were investigated using fast application of transmitters on nucleated patches and whole-cell patch-clamp recordings. At a holding potential of -60 mV and an E(Cl) close to 0 mV GABA and glycine activated inward currents with a half-maximal activation concentration of 127 microM and 353 microM, respectively. GABA(A)Rs activated and deactivated significantly faster than GlyRs (20-80% rise-time: 0.71 ms for GABA(A)Rs and 1.31 ms for GlyRs; amplitude-weighted decay time constant, tau(w), 22.4+/-1.3 ms for GABA(A)Rs and 108.7+/-32.9 ms for GlyRs). The tau(w) values for receptor desensitization were 26.8+/-1.9 ms for GABA(A)Rs and 177.9+/-47.2 ms for GlyRs. Recovery from desensitization was significantly faster for GlyRs (tau=334 ms) than for GABA(A)Rs (tau1=82 ms; tau2=3783 ms). The tau(w) values of GABA(A)R-mediated spontaneous and miniature inhibitory postsynaptic currents were not significantly different from those of GABA(A)Rs activated by fast application, but significantly different to the tau(w) of GlyRs activated by fast application. The different properties of GABA(A)Rs and GlyRs expressed in the same IC neuron suggest a distinct functional contribution to the development of inhibitory synapses in the IC.
利用在有核膜片和全细胞膜片钳记录上快速施加递质的方法，研究了大鼠下丘（IC）发育中神经元（P3 - 8）表达的γ-氨基丁酸A型受体（GABA(A)Rs）和甘氨酸受体（GlyRs）。在 - 60 mV的钳制电位和接近0 mV的氯离子平衡电位下，γ-氨基丁酸（GABA）和甘氨酸激活内向电流，其半数最大激活浓度分别为127 μM和353 μM。GABA(A)Rs的激活和失活明显快于GlyRs（20 - 80%上升时间：GABA(A)Rs为0.71 ms，GlyRs为1.31 ms；幅度加权衰减时间常数，τ(w)，GABA(A)Rs为22.4±1.3 ms，GlyRs为108.7±32.9 ms）。GABA(A)Rs受体脱敏的τ(w)值为26.8±1.9 ms，GlyRs为177.9±47.2 ms。GlyRs从脱敏状态恢复明显快于GABA(A)Rs（τ = 334 ms）（GABA(A)Rs：τ1 = 82 ms；τ2 = 3783 ms）。GABA(A)R介导的自发性和微小抑制性突触后电流的τ(w)值与快速施加激活的GABA(A)Rs的τ(w)值无显著差异，但与快速施加激活的GlyRs的τ(w)值有显著差异。在同一IC神经元中表达的GABA(A)Rs和GlyRs的不同特性表明它们对IC中抑制性突触的发育有不同的功能贡献。
