Ivanova Elena, Müller Ulrike, Wässle Heinz
Department Neuroanatomy, Max-Planck-Institute for Brain Research, Frankfurt/Main, Germany.
Eur J Neurosci. 2006 Jan;23(2):350-64. doi: 10.1111/j.1460-9568.2005.04557.x.
Glycine and gamma-aminobutyric acid (GABA) are the major inhibitory transmitters of the mammalian retina, and bipolar cells receive GABAergic and glycinergic inhibition from multiple amacrine cell types. Here we evaluated the functional properties and subunit composition of glycine receptors (GlyRs) in bipolar cells. Patch-clamp recordings were performed from retinal slices of wild-type, GlyRalpha1-deficient (Glra1(spd-ot)) and GlyRalpha3-deficient (Glra3(-/-)) mice. Whole-cell currents following glycine application and spontaneous inhibitory postsynaptic currents (IPSCs) were analysed. During the recordings the cells were filled with Alexa 488 and, thus, unequivocally identified. Glycine-induced currents of bipolar cells were picrotoxinin-insensitive and thus represent heteromeric channels composed of alpha and beta subunits. Glycine-induced currents and IPSCs were absent from all bipolar cells of Glra1(spd-ot) mice, indicating that GlyRalpha1 is an essential subunit of bipolar cell GlyRs. By comparing IPSCs of bipolar cells in wild-type and Glra3(-/-) mice, no statistically significant differences were found. OFF-cone bipolar (CB) cells receive a strong glycinergic input from AII amacrine cells, that is preferentially based on the fast alpha1beta-containing channels (mean decay time constant tau = 5.9 +/- 1.4 ms). We did not observe glycinergic IPSCs in ON-CB cells and could elicit only small, if any, glycinergic currents. Rod bipolar cells receive a prominent glycinergic input that is mainly mediated by alpha1beta-containing channels (tau = 5.5 +/- 1.6 ms). Slow IPSCs, the characteristic of GlyRs containing the alpha2 subunit, were not observed in bipolar cells. Thus, different bipolar cell types receive kinetically fast glycinergic inputs, preferentially mediated by GlyRs composed of alpha1 and beta subunits.
甘氨酸和γ-氨基丁酸（GABA）是哺乳动物视网膜的主要抑制性神经递质，双极细胞从多种无长突细胞类型接受GABA能和甘氨酸能抑制。在这里，我们评估了双极细胞中甘氨酸受体（GlyRs）的功能特性和亚基组成。对野生型、GlyRα1缺陷型（Glra1(spd-ot)）和GlyRα3缺陷型（Glra3(-/-)）小鼠的视网膜切片进行膜片钳记录。分析了施加甘氨酸后的全细胞电流和自发抑制性突触后电流（IPSCs）。在记录过程中，细胞用Alexa 488填充，从而明确识别。双极细胞的甘氨酸诱导电流对印防己毒素不敏感，因此代表由α和β亚基组成的异源通道。Glra1(spd-ot)小鼠的所有双极细胞均未出现甘氨酸诱导电流和IPSCs，表明GlyRα1是双极细胞GlyRs的必需亚基。通过比较野生型和Glra3(-/-)小鼠双极细胞的IPSCs，未发现统计学上的显著差异。视锥OFF双极（CB）细胞从AII无长突细胞接受强烈的甘氨酸能输入，这优先基于快速的含α1β通道（平均衰减时间常数τ = 5.9 +/- 1.4毫秒）。我们在视锥ON-CB细胞中未观察到甘氨酸能IPSCs，并且即使有也只能引发很小的甘氨酸能电流。视杆双极细胞接受主要由含α1β通道介导的显著甘氨酸能输入（τ = 5.5 +/- 1.6毫秒）。在双极细胞中未观察到含有α2亚基的GlyRs所特有的缓慢IPSCs。因此，不同类型的双极细胞接受动力学上快速的甘氨酸能输入，优先由由α1和β亚基组成的GlyRs介导。
