Heterogeneous distribution of taste cells in facial and vagal nerve-innervated taste buds

Taste buds were isolated from the fungiform papilla of the rat tongue and the receptor cells (TRCs) were patch clamped. Seals were obtained on the basolateral membrane of 281 TRCs, protruding from the intact taste buds or isolated by micro-dissection. In whole-cell configuration 72% of the cells had a TTX blockable transient Na inward current (mean peak amplitude 0.74 nA). All cells had outward K currents. Their activation was slower than for the Na current and a slow inactivation was also noticeable. The K currents were blocked by tetraethylammonium, Ba, and 4-aminopyridine, and were absent when the pipette contained Cs instead of K. With 100 mM Ba or 100 mM Ca in the bath, two types of inward current were observed. An L-type Ca current (ICaL) activated at -20 mV had a mean peak amplitude of 440 pA and inactivated very slowly. At 3 mM Ca the activation threshold of ICaL was near -40 mV. A transient T-type current (ICaT) activated at -50 mV had an average peak amplitude of 53 pA and inactivated with a time constant of 36 ms at -30 mV. ICaL was blocked more efficiently by Cd and D600 than ICaT. ICaT was blocked by 0.2 mM Ni and half blocked by 200 microM amiloride. In whole-cell voltage clamp, Na-saccharin caused (in 34% of 55 cells tested) a decrease in outward K currents by 21%, which may be expected to depolarize the TRCs. Also, Na-saccharin caused some taste cells to fire action potentials (on-cell, 7 out of 24 cells; whole-cell, 2 out of 38 cells responding to saccharin) of amplitudes sufficient to activate ICaL. Thus the action potentials will cause Ca inflow, which may trigger release of transmitter.

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Identification of electrophysiologically distinct cell subpopulations in Necturus taste buds.

The Journal of General Physiology ◽

10.1085/jgp.102.1.143 ◽

1993 ◽

Vol 102 (1) ◽

pp. 143-170 ◽

Cited By ~ 20

Author(s):

A Bigiani ◽

S D Roper

Keyword(s):

Lucifer Yellow ◽

Taste Buds ◽

Taste Bud ◽

Basal Cells ◽

Patch Clamp Technique ◽

Lingual Epithelium ◽

Voltage Gated ◽

Receptor Cells ◽

Taste Cells ◽

K Currents

We used the patch clamp technique to record from taste cells in thin transverse slices of lingual epithelium from Necturus maculosus. In this preparation, the epithelial polarity and the cellular organization of the taste buds, as well as the interrelationships among cells within the taste bud, were preserved. Whole-cell recording, combined with cell identification using Lucifer yellow, allowed us to identify distinct subpopulations of taste cells based on their electrophysiological properties. Receptor cells could be divided in two groups: one group was characterized by the presence of voltage-gated Na+, K+, and Ca2+ currents; the other group was characterized by the presence of K+ currents only. Therefore, receptor cells in the first group would be expected to be capable of generating action potentials, whereas receptor cells in the second group would not. Basal taste cells could also be divided into two different groups. Some basal cells possessed voltage-gated Na+, K+, and Ca2+ conductances, whereas other basal cells only had K+ conductance. In addition to single taste cells, we were able to identify electrically coupled taste cells. We monitored cell-cell coupling by measuring membrane capacitance and by observing Lucifer yellow dye coupling. Electrical coupling in pairs of dye-coupled taste receptor cells was strong, as indicated by experiments with the uncoupling agent 1-octanol. Electrically coupled receptor cells possessed voltage-gated currents, including Na+ and K+ currents. The electrophysiological differentiation among taste cells presumably is related to functional diversifications, such as different chemosensitivities.

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GAD65Cre drives reporter expression in multiple taste cell types

10.1101/2021.01.14.426727 ◽

2021 ◽

Author(s):

Eric D. Larson ◽

Aurelie Vandenbeuch ◽

Catherine B. Anderson ◽

Sue C. Kinnamon

Keyword(s):

Cell Function ◽

Cell Types ◽

Taste Cell ◽

Taste Buds ◽

Specific Marker ◽

Type I ◽

Chorda Tympani ◽

Type I Cells ◽

Taste Cells ◽

I Cells

ABSTRACTIn taste buds, Type I cells represent the majority of cells (50-60%) and primarily have a glial-like function in taste buds. However, recent studies suggest that they have additional sensory and signaling functions including amiloride-sensitive salt transduction, oxytocin modulation of taste, and substance P mediated GABA release. Nonetheless, the overall function of Type I cells in transduction and signaling remains unclear, primarily because of the lack of a reliable reporter for this cell type. GAD65 expression is specific to Type I taste cells and GAD65 has been used as a Cre driver to study Type I cells in salt taste transduction. To test the specificity of transgene-driven expression, we crossed GAD65Cre mice with floxed tdTomato and Channelrhodopsin (ChR2) lines and examined the progeny with immunochemistry, chorda tympani recording, and calcium imaging. We report that while many tdTomato+ taste cells express NTPDase2, a specific marker of Type I cells, we see expression of tdTomato in both Gustducin and SNAP25 positive taste cells. We also see ChR2 in cells just outside the fungiform taste buds. Chorda tympani recordings in the GAD65Cre/ChR2 mice show large responses to blue light, larger than any response to standard taste stimuli. Further, several isolated tdTomato positive taste cells responded to KCl depolarization with increases in intracellular calcium, indicating the presence of voltage-gated calcium channels. Taken together, these data suggest that GAD65Cre mice drive expression in multiple taste cell types and thus cannot be considered a reliable reporter of Type I cell function.

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Isolating Taste Buds and Taste Cells from Vallate Papillae of C57BL/6J Mice for Detecting Transmitter Secretion

BIO-PROTOCOL ◽

10.21769/bioprotoc.1824 ◽

2016 ◽

Vol 6 (11) ◽

Author(s):

Anthony Huang ◽

Sandy Wu

Keyword(s):

Taste Buds ◽

Transmitter Secretion ◽

Taste Cells ◽

Vallate Papillae

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Embryonic taste buds develop in the absence of innervation

Development ◽

10.1242/dev.122.4.1103 ◽

1996 ◽

Vol 122 (4) ◽

pp. 1103-1111 ◽

Cited By ~ 2

Author(s):

L.A. Barlow ◽

C.B. Chien ◽

R.G. Northcutt

Keyword(s):

Embryonic Development ◽

Taste Receptor ◽

Nerve Fibers ◽

Taste Buds ◽

Taste Bud ◽

Taste Cells ◽

Experimental Approaches ◽

Well Differentiated ◽

Serotonin Immunoreactivity

It has been hypothesized that taste buds are induced by contact with developing cranial nerve fibers late in embryonic development, since descriptive studies indicate that during embryonic development taste cell differentiation occurs concomitantly with or slightly following the advent of innervation. However, experimental evidence delineating the role of innervation in taste bud development is sparse and equivocal. Using two complementary experimental approaches, we demonstrate that taste cells differentiate fully in the complete absence of innervation. When the presumptive oropharyngeal region was taken from a donor axolotl embryo, prior to its innervation and development of taste buds, and grafted ectopically on to the trunk of a host embryo, the graft developed well-differentiated taste buds. Although grafts were invaded by branches of local spinal nerves, these neurites were rarely found near ectopic taste cells. When the oropharyngeal region was raised in culture, numerous taste buds were generated in the complete absence of neural elements. Taste buds in grafts and in explants were identical to those found in situ both in terms of their morphology and their expression of calretinin and serotonin immunoreactivity. Our findings indicate that innervation is not necessary for complete differentiation of taste receptor cells. We propose that taste buds are either induced in response to signals from other tissues, such as the neural crest, or arise independently through intrinsic patterning of the local epithelium.

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Acid-Sensitive Two-Pore Domain Potassium (K2P) Channels in Mouse Taste Buds

Journal of Neurophysiology ◽

10.1152/jn.00273.2004 ◽

2004 ◽

Vol 92 (3) ◽

pp. 1928-1936 ◽

Cited By ~ 81

Author(s):

Trevor A. Richter ◽

Gennady A. Dvoryanchikov ◽

Nirupa Chaudhari ◽

Stephen D. Roper

Keyword(s):

Ion Channels ◽

Potassium Channels ◽

Taste Receptor ◽

Taste Buds ◽

Confocal Imaging ◽

Intracellular Acidification ◽

Pharmacological Characterization ◽

Taste Cells ◽

Pore Domain ◽

And Task

Sour (acid) taste is postulated to result from intracellular acidification that modulates one or more acid-sensitive ion channels in taste receptor cells. The identity of such channel(s) remains uncertain. Potassium channels, by regulating the excitability of taste cells, are candidates for acid transducers. Several 2-pore domain potassium leak conductance channels (K2P family) are sensitive to intracellular acidification. We examined their expression in mouse vallate and foliate taste buds using RT-PCR, and detected TWIK-1 and -2, TREK-1 and -2, and TASK-1. Of these, TWIK-1 and TASK-1 were preferentially expressed in taste cells relative to surrounding nonsensory epithelium. The related TRESK channel was not detected, whereas the acid-insensitive TASK-2 was. Using confocal imaging with pH-, Ca2+-, and voltage-sensitive dyes, we tested pharmacological agents that are diagnostic for these channels. Riluzole (500 μM), selective for TREK-1 and -2 channels, enhanced acid taste responses. In contrast, halothane (≤ ∼17 mM), which acts on TREK-1 and TASK-1 channels, blocked acid taste responses. Agents diagnostic for other 2-pore domain and voltage-gated potassium channels (anandamide, 10 μM; Gd3+, 1 mM; arachidonic acid, 100 μM; quinidine, 200 μM; quinine, 100 mM; 4-AP, 10 mM; and TEA, 1 mM) did not affect acid responses. The expression of 2-pore domain channels and our pharmacological characterization suggest that a matrix of ion channels, including one or more acid-sensitive 2-pore domain K channels, could play a role in sour taste transduction. However, our results do not unambiguously identify any one channel as the acid taste transducer.

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Mouse mandibular retromolar taste buds associated with a mucus salivary gland

Chemical Senses ◽

10.1093/chemse/bjab019 ◽

2021 ◽

Author(s):

Quan T Nguyen ◽

Grace E Beck Coburn ◽

Amber Valentino ◽

Bekir Karabucak ◽

Marco Tizzano

Keyword(s):

Salivary Gland ◽

Fluorescent Protein ◽

Minor Salivary Gland ◽

Immunohistochemical Analysis ◽

Taste Buds ◽

Taste Bud ◽

Neuronal Marker ◽

Taste Cells ◽

Green Fluorescent ◽

A Minor

Abstract We have characterized a recently rediscovered chemosensory structure at the rear of the mandibular mucosa in the mouse oral cavity originally reported in the 1980s. This consists of unorganized taste buds, not contained within troughs, associated with the ducts of an underlying minor salivary gland. Using whole-mount preparations of transgenic mice expressing green fluorescent protein under the promoter of taste-signaling-specific genes, we determined that the structure contains taste bud clusters and salivary gland orifices at the rear of each mandible, distal to the last molar and anterior to the ascending ramus. Immunohistochemical analysis show in the retromolar taste buds expression of the taste receptors Tas2R131 and T1R3 and taste cascade molecules TrpM5, PLCβ2, and GNAT3, consistent with type II taste cells, and expression of GAD1, consistent with type III taste cells. Furthermore, the neuronal marker CGRP in retromolar mucosa tissue wrapping around TrpM5+ taste buds was observed. RT-PCR showed that retromolar taste buds express all three mouse tas1r genes, 28 of the 35 tas2r genes, and taste transduction signaling genes gnat3, plcb2, and trpm5, making the retromolar TBs similar to other lingual and palate taste buds. Finally, histochemistry demonstrated that the mandibular retromolar secretory gland is a minor salivary gland of mucous type. The mandibular retromolar taste structure may thus play a role in taste sensation and represent a potential novel pharmacological target for taste disorders.

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“Tripartite Synapses” in Taste Buds: A Role for Type I Glial-like Taste Cells

Journal of Neuroscience ◽

10.1523/jneurosci.1444-21.2021 ◽

2021 ◽

pp. JN-RM-1444-21

Author(s):

Yuryanni A. Rodriguez ◽

Jennifer K. Roebber ◽

Gennady Dvoryanchikov ◽

Vivien Makhoul ◽

Stephen D. Roper ◽

...

Keyword(s):

Taste Buds ◽

Type I ◽

Taste Cells

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