title: Time-dependent expression of hypertonic effects on bullfrog taste nerve responses to salts and bitter substances.
abstract: We previously showed that the hypertonicity of taste stimulating solutions modified tonic responses, the quasi-steady state component following the transient (phasic) component of each integrated taste nerve response. Here we show that the hypertonicity opens tight junctions surrounding taste receptor cells in a time-dependent manner and modifies whole taste nerve responses in bullfrogs. We increased the tonicity of stimulating solutions with non-taste substances such as urea or ethylene glycol. The hypertonicity enhanced phasic responses to NaCl>0.2M, and suppressed those to NaCl<0.1M, 1mM CaCl2, and 1mM bitter substances (quinine, denatonium and strychnine). The hypertonicity also enhanced the phasic responses to a variety of 0.5M salts such as LiCl and KCl. The enhancing effect was increased by increasing the difference between the ionic mobilities of the cations and anions in the salt. A preincubation time >20s in the presence of 1M non-taste substances was needed to elicit both the enhancing and suppressing effects. Lucifer Yellow CH, a paracellular marker dye, diffused into bullfrog taste receptor organs in 30s in the presence of hypertonicity. These results agreed with our proposed mechanism of hypertonic effects that considered the diffusion potential across open tight junctions.
authors: Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Hibikino 2-4, Kitakyushu-shi 808-0196, Japan.
authors: Kazunori
authors: K
authors: Mashiyama
authors: Department of Life Science and Green Chemistry, Saitama Institute of Technology, Fukaya 369-0293, Japan.
authors: Yuhei
authors: Y
authors: Nozawa
authors: Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Hibikino 2-4, Kitakyushu-shi 808-0196, Japan.
authors: Yoshitaka
authors: Y
authors: Ohtubo
authors: Graduate School of Engineering, Saitama Institute of Technology, Fukaya 369-0293, Japan.
authors: Takashi
authors: T
authors: Kumazawa
authors: Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Hibikino 2-4, Kitakyushu-shi 808-0196, Japan. Electronic address: yoshii@brain.kyutech.ac.jp.
authors: Kiyonori
authors: K
authors: Yoshii
mesh_terms: D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005930:Glossopharyngeal Nerve / Q000166:cytology*; D007546:Isoquinolines / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D011892:Rana catesbeiana; D012492:Salts / Q000494:pharmacology*; D011984:Sensory Receptor Cells / Q000187:drug effects*; D013649:Taste / Q000187:drug effects / Q000502:physiology*; D013650:Taste Buds / Q000166:cytology / Q000187:drug effects*; D013997:Time Factors
chemical_list: D007546:Isoquinolines; D012492:Salts; C017475:lucifer yellow; D011803:Quinine; D002122:Calcium Chloride
keywords: Diffusion potentials; Glossopharyngeal nerves; Local circuit currents; Tight junctions