| Summary: | 博士 === 國立陽明大學 === 神經科學研究所 === 98 === Acid-sensing ion channels (ASICs) belong to degenerin/epithelial Na+ channel family and are widely distributed in brains. They are voltage-independent Na+ channels, which can be activated by extracellular H+. ASIC currents in hippocampal GABAergic inhibitory interneurons are larger than pyramidal neurons (PNs) and preferentially conducted to terminate seizures. However, exact characteristics and compositions of native ASICs in interneurons of numerous types remain unclear. Nucleated patch recordings and single-cell RT-PCR were combined to study ASICs in interneurons of rat hippocampal acute brain slices. We uncovered cell type-specific ASIC expression in dendritic and perisomatic inhibitory interneurons. Our results show that O-LM cells (O-LMs) of dendritic inhibition exhibited about 6-fold ASIC current density higher than PNs in CA1 subfield. Surprisingly, perisomatic inhibitory basket cells (BCs) in dentate gyrus expressed comparable ASIC currents to PNs. By non-stationary fluctuation analysis, we found more ASICs in O-LMs account for the larger ASIC current density. Furthermore, different gating and mRNA expression suggested that the subunit compositions of ASICs are ASIC1a/2a in O-LMs and ASIC1a in BCs. Besides, sensitivity to the specific antagonist of ASIC1a homomers, psalmotoxin 1, indicated that ASICs in BCs are ASIC1a homomers. Functional ASIC currents were also expressed on dendrites of these three neuronal types. Here, we demonstrate channel number, gating and subunit compositions of ASICs are heterogeneously expressed among PNs, dendritic and perisomatic inhibitory interneurons. By providing comparisons of ASICs in interneurons, our findings are potentially important to distinct roles of interneurons in physiology and pathology.
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