Bindokas V P, Ishida A T
Department of Animal Physiology, University of California, Davis 95616.
Proc Natl Acad Sci U S A. 1991 Dec 1;88(23):10759-63. doi: 10.1073/pnas.88.23.10759.
Of the various synaptic inputs known to converge upon retinal ganglion cells, the major inhibitory inputs are thought to be GABAergic. Although gamma-aminobutyric acid (GABA) is known to activate anion-selective ion channels in retinal ganglion cells, we have tested the possibility that GABA can also modulate cationic conductances in these cells, as seen in other central and peripheral neurons. Specifically, we have made whole-cell patch-clamp recordings to test whether voltage-gated calcium currents in isolated goldfish retinal ganglion cells are sensitive to GABAB receptor ligands. (-)-Baclofen and GABA inhibited calcium currents activated by moderately long depolarizations and, during large depolarizations (e.g., to 0 mV), also appeared to accelerate the rate of current decay. The calcium current inhibition induced by (-)-baclofen and GABA was not prevented by 2-hydroxysaclofen, phaclofen, or bicuculline, even though bicuculline suppressed a GABA-activated conductance in these cells. These results demonstrate the presence of baclofen- and GABA-sensitive calcium currents in vertebrate retinal ganglion cells as well as the coexistence of GABAA and GABAB receptors in individual retinal ganglion cells.
在已知汇聚于视网膜神经节细胞的各种突触输入中，主要的抑制性输入被认为是γ-氨基丁酸（GABA）能的。尽管已知γ-氨基丁酸（GABA）可激活视网膜神经节细胞中的阴离子选择性离子通道，但我们已经测试了GABA是否也能像在其他中枢和外周神经元中那样调节这些细胞中的阳离子电导。具体而言，我们进行了全细胞膜片钳记录，以测试分离的金鱼视网膜神经节细胞中的电压门控钙电流是否对GABAB受体配体敏感。（-）-巴氯芬和GABA抑制了由适度长时间去极化激活的钙电流，并且在大的去极化（例如，到0 mV）期间，似乎还加速了电流衰减速率。即使荷包牡丹碱抑制了这些细胞中GABA激活的电导，（-）-巴氯芬和GABA诱导的钙电流抑制也未被2-羟基巴氯芬、法氯芬或荷包牡丹碱所阻止。这些结果证明了脊椎动物视网膜神经节细胞中存在对巴氯芬和GABA敏感的钙电流，以及单个视网膜神经节细胞中GABAA和GABAB受体的共存。
