Cell-Type-Independent Expression of Inwardly Rectifying Potassium Currents in Mouse Fungiform Taste Bud Cells

Abstract

Inwardly rectifying potassium (Kir) channels play key roles in functions, including maintaining the resting membrane potential and regulating the action potential duration in excitable cells. Using in situ whole-cell recordings, we investigated Kir currents in mouse fungiform taste bud cells (TBCs) and immunologically identified the cell types (type I-III) expressing these currents. We demonstrated that Kir currents occur in a cell-type-independent manner. The activation potentials we measured were -80 to -90 mV, and the magnitude of the currents increased as the membrane potentials decreased, irrespective of the cell types. The maximum current densities at -120 mV showed no significant differences among cell types (p>0.05, one-way ANOVA). The density of Kir currents was not correlated with the density of either transient inward currents or outwardly rectifying currents, although there was significant correlation between transient inward and outwardly rectifying current densities (p<0.05, test for no correlation). RT-PCR studies employing total RNA extracted from peeled lingual epithelia detected mRNAs for Kir1, Kir2, Kir4, Kir6, and Kir7 families. These findings indicate that TBCs express several types of Kir channels functionally, which may contribute to regulation of the resting membrane potential and signal transduction of taste.

Age‐related electrophysiological changes in mouse taste receptor cells

“…Each epithelium contained only one cell that was examined via electro- or SNAP-25. The confocal images obtained were similar to those described previously (Iwamoto et al, 2020;Kimura et al, 2014;Nakao et al, 2020). We investigated a total of 24 cells: 12 cells for both action potentials and voltage-gated currents and 12 cells for voltage-gated currents only.…”

“…Immediately after obtaining the electrophysiological recordings, we soaked the recording platform in a fixative solution to fix the epithelium, and we immunologically identified the types of the investigated cells (Iwamoto et al, 2020;Kimura et al, 2014;Nakao, Koshimura, Yamasaki, & Ohtubo, 2020;Ohtubo et al, 2012). Briefly,…”

“…Immediately after obtaining the electrophysiological recordings, we soaked the recording platform in a fixative solution to fix the epithelium, and we immunologically identified the types of the investigated cells (Iwamoto et al, 2020;Kimura et al, 2014;Nakao, Koshimura, Yamasaki, & Ohtubo, 2020;Ohtubo et al, 2012). Briefly, we injected biocytin during electrophysiological recordings, fixed the epithelium with a fixative solution overnight, and immunostained the epithelium with primary antibodies dissolved in a blocking solution for 24-48 h at 4 • C. After washing the epithelium with phosphatebuffered saline (PBS), we incubated it with Alexa Fluor-conjugated secondary antibodies for 24-48 h at 4…”

Characteristics of A-type voltage-gated K+ currents expressed on sour-sensing type III taste receptor cells in mice

“…Conventional whole-cell voltage-clamp conditions were utilized according to previous studies (Nakao et al 2020 ; Ohtubo 2021 ; Takeuchi et al 2011 ). In brief, electrical responses were recorded with electrodes (ca.…”