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J Physiol Volume 584, Number 2, 473-488, October 15, 2007 DOI: 10.1113/jphysiol.2007.138370
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NEUROSCIENCE

Functional expression of ionotropic purinergic receptors on mouse taste bud cells

 Ryotaro Hayato1, Yoshitaka Ohtubo1 and Kiyonori Yoshii1

1 Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Hibikino 2-4, Kitakyushu 808-0196, Japan

Neurotransmitter receptors on taste bud cells (TBCs) and taste nerve fibres are likely to contribute to taste transduction by mediating the interaction among TBCs and that between TBCs and taste nerve fibres. We investigated the functional expression of P2 receptor subtypes on TBCs of mouse fungiform papillae. Electrophysiological studies showed that 100 µM ATP applied to their basolateral membranes either depolarized or hyperpolarized a few cells per taste bud. Ca2+ imaging showed that similarly applied 1 µM ATP, 30 µM BzATP (a P2X7 agonist), or 1 µM 2MeSATP (a P2Y1 and P2Y11 agonist) increased intracellular Ca2+ concentration, but 100 µM UTP (a P2Y2 and P2Y4 agonist) and {alpha},beta-meATP (a P2X agonist except for P2X2, P2X4 and P2X7) did not. RT-PCR suggested the expression of P2X2, P2X4, P2X7, P2Y1, P2Y13 and P2Y14 among the seven P2X subtypes and seven P2Y subtypes examined. Immunohistostaining confirmed the expression of P2X2. The exposure of the basolateral membranes to 3 mM ATP for 30 min caused the uptake of Lucifer Yellow CH in a few TBCs per taste bud. This was antagonized by 100 µM PPADS (a non-selective P2 blocker) and 1 µM KN-62 (a P2X7 blocker). These results showed for the first time the functional expression of P2X2 and P2X7 on TBCs. The roles of P2 receptor subtypes in the taste transduction, and the renewal of TBCs, are discussed.

(Received 12 June 2007; accepted after revision 15 August 2007; first published online 16 August 2007)
Corresponding author K. Yoshii: Kyushu Institute of Technology, Hibikino 2-4, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu 808-0196, Japan. Email: yoshii{at}brain.kyutech.ac.jp






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