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Inwardly rectifying potassium channels in rat retinal ganglion cells
Author(s) -
Chen Ling,
Yu YongChun,
Zhao JingWei,
Yang XiongLi
Publication year - 2004
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2004.03553.x
Subject(s) - g protein coupled inwardly rectifying potassium channel , inward rectifier potassium ion channel , patch clamp , potassium channel , microbiology and biotechnology , hyperpolarization (physics) , neuroscience , endoplasmic reticulum , chemistry , retina , biophysics , biology , g protein , ion channel , receptor , electrophysiology , biochemistry , signal transduction , organic chemistry , nuclear magnetic resonance spectroscopy
Inwardly rectifying potassium channels (Kir channels) are important for neuronal signalling and membrane excitability. In the present work we characterized, for the first time, Kir channels in rat retinal ganglion cells (RGCs), the output neurons in the retina, using immunocytochemical and patch‐clamp techniques. Various subunits of Kir channels (Kir1.1, 2.1, 2.3, 3.1, 3.2 and 3.3) were expressed in RGCs, but with distinct subcellular localization. Kir1.1 was mainly expressed in axons of RGCs. Kir2.1 and Kir2.3 were both present in somata of RGCs. Whereas staining for Kir3.1 was profoundly present in an endoplasmic reticulum‐like structure and Kir3.2 was strongly expressed in the cytoplasm and the cytomembrane of somata, dendrites and axons of RGCs, faint, sparse labelling for Kir3.3 was seen in the cytomembrane. Immunoreactivity for Kir4.1 and Kir4.2 was not detectable in RGCs. Whole‐cell currents mediated by Kir channels were recorded in isolated RGCs and they differed from hyperpolarization‐activated currents (I h ) by showing full activation in < 10 ms, no inactivation, and being significantly suppressed by 300 µ m Ba 2+ . Unlike in retinal horizontal cells and bipolar cells, these currents were mainly mediated by G‐protein‐coupled Kir3 (GIRK) channels, as demonstrated by the fact that GDP β S and GTP γ S included in the pipette solution markedly decreased and increased the currents, respectively. Furthermore, the GIRK channels were probably coupled to GABA B receptors, because baclofen considerably increased the Kir currents and the increased currents were suppressed by Ba 2+ . These characteristics of the Kir currents provide more versatility for signalling of RGCs.