Effects of 4,9-anhydrotetrodotoxin on voltage-gated Na+ channels of mouse vas deferens myocytes and recombinant NaV1.6 channels

Kohei Takahara, Tadashi Yamamoto, Keiichiro Uchida, Hai Lei Zhu, Atsushi Shibata, Tetsuichiro Inai, Mitsuru Noguchi, Mari Yotsu-Yamashita, Noriyoshi Teramoto

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    1 Citation (Scopus)

    Abstract

    Molecular investigations were performed in order to determine the major characteristics of voltage-gated Na+ channel β-subunits in mouse vas deferens. The use of real-time quantitative PCR showed that the expression of Scn1b was significantly higher than that of other β-subunit genes (Scn2b – Scn4b). Immunoreactivity of Scn1b proteins was also detected in the inner circular and outer longitudinal smooth muscle of mouse vas deferens. In whole-cell recordings, the actions of 4,9-anhydroTTX on voltage-gated Na+ current peak amplitude in myocytes (i.e., native INa) were compared with its inhibitory potency on recombinant NaV1.6 channels (expressed in HEK293 cells). A depolarizing rectangular voltage-pulse elicited a fast and transient inward native INa and recombinant NaV1.6 expressed in HEK293 cells (i.e., recombinant INa). The current decay of native INa was similar to the recombinant NaV1.6 current co-expressed with β1-subunits. The current-voltage (I-V) relationships of native INa were similar to those of recombinant NaV1.6 currents co-expressed with β1-subunits. Application of 4,9-anhydroTTX inhibited the peak amplitude of native INa (Ki = 510 nM), recombinant INa (Ki = 112 nM), and recombinant INa co-expressed with β1-subunits (Ki = 92 nM). The half-maximal (Vhalf) activation and inactivation of native INa values were similar to those observed in recombinant INa co-expressed with β1-subunits. These results suggest that β1-subunit proteins are likely to be expressed mainly in the smooth muscle layers of murine vas deferens and that 4,9-anhydroTTX inhibited not only native INa but also recombinant INa and recombinant INa co-expressed with β1-subunits in a concentration-dependent manner.

    Original languageEnglish
    Pages (from-to)489-499
    Number of pages11
    JournalNaunyn-Schmiedeberg's Archives of Pharmacology
    Volume391
    Issue number5
    DOIs
    Publication statusPublished - 2018 May 1

    Keywords

    • 4,9-Anhydrotetrodotoxin
    • Mouse vas deferens
    • Na1.6 channels
    • Smooth muscle-type Na
    • β-subunit

    ASJC Scopus subject areas

    • Pharmacology

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