title: Cell-type-dependent action potentials and voltage-gated currents in mouse fungiform taste buds.
abstract: Taste receptor cells fire action potentials in response to taste substances to trigger non-exocytotic neurotransmitter release in type II cells and exocytotic release in type III cells. We investigated possible differences between these action potentials fired by mouse taste receptor cells using in situ whole-cell recordings, and subsequently we identified their cell types immunologically with cell-type markers, an IP3 receptor (IP3 R3) for type II cells and a SNARE protein (SNAP-25) for type III cells. Cells not immunoreactive to these antibodies were examined as non-IRCs. Here, we show that type II cells and type III cells fire action potentials using different ionic mechanisms, and that non-IRCs also fire action potentials with either of the ionic mechanisms. The width of action potentials was significantly narrower and their afterhyperpolarization was deeper in type III cells than in type II cells. Na(+) current density was similar in type II cells and type III cells, but it was significantly smaller in non-IRCs than in the others. Although outwardly rectifying current density was similar between type II cells and type III cells, tetraethylammonium (TEA) preferentially suppressed the density in type III cells and the majority of non-IRCs. Our mathematical model revealed that the shape of action potentials depended on the ratio of TEA-sensitive current density and TEA-insensitive current one. The action potentials of type II cells and type III cells under physiological conditions are discussed.
authors.affiliation: Graduate school of Life Science and Systems Engineering, Kyushu Institute of Technology, Hibikino 2-4, Kitakyushu-shi, 808-0196, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Kimura
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Ohtubo
authors.forename: Katsumi
authors.initials: K
authors.lastname: Tateno
authors.forename: Keita
authors.initials: K
authors.lastname: Takeuchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kumazawa
authors.forename: Kiyonori
authors.initials: K
authors.lastname: Yoshii
mesh_terms: D000200:Action Potentials; D000818:Animals; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008959:Models, Neurological; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism; D013650:Taste Buds / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology; D061566:Voltage-Gated Sodium Channels / Q000378:metabolism*
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C494209:Snap25 protein, mouse; D050825:Synaptosomal-Associated Protein 25; D061566:Voltage-Gated Sodium Channels; D019789:Tetraethylammonium; D012964:Sodium
keywords: computer simulation; immunohistostaining; patch-clamping; taste receptor cells