Ionic currents recorded from the basolateral and receptor membranes of mouse taste cells

Evidence implicates a number of neuroactive substances and their receptors in mediating complex cell-to-cell communications in the taste bud. Recently, we found that ATP, a ubiquitous neurotransmitter/neuromodulator, mobilizes intracellular Ca2+ in taste cells by activating P2Y receptors. Here, P2Y receptor-cellular response coupling was characterized in detail using single cell ratio photometry and the inhibitory analysis. The sequence of underlying events was shown to include ATP-dependent activation of PLC, IP3 production, and IP3 receptor-mediated Ca2+ release followed by Ca2+ influx. Data obtained favor SOC channels rather than receptor-operated channels as a pathway for Ca2+ influx that accompanies Ca2+ release. Intracellular Ca2+ mobilized by ATP is apparently extruded by the plasma membrane Ca2+-ATPase, while a contribution of the Na+/Ca2+ exchange and other mechanisms of Ca2+ clearance is negligible. Cyclic AMP-dependent phosphorylation is likely to control a gain of the phosphoinositide cascade involved in ATP transduction. ATP-responsive taste cells are abundant in circumvallate, foliate, and fungiform papillae. Taken together, our observations point to a putative role for ATP as a neurotransmitter operative in the taste bud.

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Umami Responses in Mouse Taste Cells Indicate More than One Receptor

Journal of Neuroscience ◽

10.1523/jneurosci.4329-05.2006 ◽

2006 ◽

Vol 26 (8) ◽

pp. 2227-2234 ◽

Cited By ~ 102

Author(s):

Y. Maruyama

Keyword(s):

Taste Cells ◽

Mouse Taste

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Sodium/Calcium Exchangers Selectively Regulate Calcium Signaling in Mouse Taste Receptor Cells

Journal of Neurophysiology ◽

10.1152/jn.00118.2010 ◽

2010 ◽

Vol 104 (1) ◽

pp. 529-538 ◽

Cited By ~ 13

Author(s):

Steven A. Szebenyi ◽

Agnieszka I. Laskowski ◽

Kathryn F. Medler

Keyword(s):

Calcium Release ◽

Calcium Influx ◽

Taste Receptor ◽

Physiological Role ◽

Cytosolic Calcium ◽

Calcium Signals ◽

Sodium Calcium ◽

Signaling Mechanisms ◽

Taste Cells ◽

Mouse Taste

Taste cells use multiple signaling mechanisms to generate appropriate cellular responses to discrete taste stimuli. Some taste stimuli activate G protein coupled receptors (GPCRs) that cause calcium release from intracellular stores while other stimuli depolarize taste cells to cause calcium influx through voltage-gated calcium channels (VGCCs). While the signaling mechanisms that initiate calcium signals have been described in taste cells, the calcium clearance mechanisms (CCMs) that contribute to the termination of these signals have not been identified. In this study, we used calcium imaging to define the role of sodium-calcium exchangers (NCXs) in the termination of evoked calcium responses. We found that NCXs regulate the calcium signals that rely on calcium influx at the plasma membrane but do not significantly contribute to the calcium signals that depend on calcium release from internal stores. Our data indicate that this selective regulation of calcium signals by NCXs is due primarily to their location in the cell rather than to the differences in cytosolic calcium loads. This is the first report to define the physiological role for any of the CCMs utilized by taste cells to regulate their evoked calcium responses.

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Sweet Taste Responses of Mouse Chorda Tympani Neurons: Existence of Gurmarin-Sensitive and -Insensitive Receptor Components

Journal of Neurophysiology ◽

10.1152/jn.1999.81.6.3087 ◽

1999 ◽

Vol 81 (6) ◽

pp. 3087-3091 ◽

Cited By ~ 22

Author(s):

Yuzo Ninomiya ◽

Toshiaki Imoto ◽

Tadataka Sugimura

Keyword(s):

Sweet Taste ◽

The Other ◽

Chorda Tympani ◽

Chorda Tympani Nerve ◽

Inhibitory Effects ◽

Single Fibers ◽

Taste Cells ◽

C57bl Mice ◽

Mouse Taste

Sweet taste responses of mouse chorda tympani neurons: existence of gurmarin-sensitive and -insensitive receptor components. Inhibitory effects of gurmarin (gur) on responses to sucrose and other sweeteners of single fibers of the chorda tympani nerve in C57BL mice were examined. Of 30 single fibers that strongly responded to 0.5 M sucrose but were not or to lesser extent responsive to 0.1 M NaCl, 0.01 M HCl, and 0.02 M quinine HCl (sucrose-best fibers), 16 fibers showed large suppression of responses to sucrose and other sweeteners by lingual treatment with 4.8 μM (∼20 μg/ml) gur (suppressed to 4–52% of control: gur-sensitive fibers), whereas the remaining 14 fibers showed no such gur inhibition (77–106% of control: gur-insensitive fibers). In gur-sensitive fibers, responses to sucrose inhibited by gur recovered to ∼70% of control responses after rinsing the tongue with 15 mM β-cyclodextrin and were almost abolished by further treatment with 2% pronase. In gur-insensitive fibers, sucrose responses were not inhibited by gur, but were largely suppressed by pronase. These results suggest existence of two different receptor components for sweeteners with different susceptibilities to gur in mouse taste cells, one gur sensitive and the other gur insensitive. Taste cells possessing each component may be specifically innervated by a particular type of chorda tympani neurons.

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