Identification of electrophysiologically distinct subpopulations of rat taste cells

Akabas, Myles H.; Dodd, Jane; Al‐Awqati, Qais

doi:10.1007/bf01869386

Cited by 39 publications

(28 citation statements)

References 38 publications

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“…While a quasi-L-type Ca current was found in amphibian TRCs , Ca currents were not previously demonstrated in the mammalian taste buds (Spielman et al, 1989;Akabas et al, 1990). Here we report that TRCs from the rat fungiform papilla have a low and high threshold calcium current, as in a variety of other excitable cells (for review see Bean, 1989).…”

Section: Two Types Of Ca Currentsmentioning

confidence: 86%

“…Less patch clamp data are available for mammals. In the rat, only 10% of TRCs isolated from the circumvallate papilla were reported to have a transient Na inward current (Akabas et al, 1988(Akabas et al, , 1990, whereas in the mouse this current was present in half of the cells (Spielman et al, 1989).…”

Section: Characteristics Of the Trcsmentioning

confidence: 99%

“…Available data are restricted to cells from the circumvallate papilla. One study concerned with the bitter response describes only a few cells with transient Na inward currents (Akabas et al, 1988(Akabas et al, , 1990. Denatonium, a strong bitter tastant, caused release of Ca from intracellular stores.…”

Section: Introductionmentioning

confidence: 99%

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Membrane currents in taste cells of the rat fungiform papilla. Evidence for two types of Ca currents and inhibition of K currents by saccharin.

Béhé

DeSimone

Avenet

et al. 1990

The Journal of General Physiology

171

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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 hA). 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 ICa L was near -40 mV. A transient T-type current (/CAT) activated at -50 mV had an average peak amplitude of 53 pA and inactivated with a time constant of 36 ms at -30 inV. ICR L was blocked more efficiently by Cd and D600 than/Ca T. ICa T was blocked by 0.2 mM Ni and half blocked by 200 #M 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/CAL. ThUS the action potentials will cause Ca inflow, which may trigger release of transmitter.

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Section: Two Types Of Ca Currentsmentioning

confidence: 86%

Section: Characteristics Of the Trcsmentioning

confidence: 99%

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Membrane currents in taste cells of the rat fungiform papilla. Evidence for two types of Ca currents and inhibition of K currents by saccharin.

Béhé

DeSimone

Avenet

et al. 1990

The Journal of General Physiology

171

View full text Add to dashboard Cite

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“…Taste cells in adult mammals are functionally heterogeneous as to the expression of voltage-dependent ion currents (Akabas et al, 1990;Béhé et al, 1990;Chen et al, 1996;Kossel et al, 1997;Bigiani, 2001). Accordingly, in a first series of experiments we studied the membrane currents elicited in mouse taste cells by depolarizing voltage steps from a reference holding potential of Ϫ84 mV (LJP corrected).…”

Section: Functional Populations Of Taste Cells During Developmentmentioning

confidence: 99%

Postnatal Development of Membrane Excitability in Taste Cells of the Mouse Vallate Papilla

et al. 2002

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The mammalian peripheral taste system undergoes functional changes during postnatal development. These changes could reflect age-dependent alterations in the membrane properties of taste cells, which use a vast array of ion channels for transduction mechanisms. Yet, scarce information is available on the membrane events in developing taste cells. We have addressed this issue by studying voltage-dependent Na ϩ , K ϩ , and Cl Ϫ currents (I Na , I K , and I Cl , respectively) in a subset of taste cells (the so-called "Na/OUT" cells, which are electrically excitable and thought to be sensory) from mouse vallate papilla. Voltage-dependent currents play a key role during taste transduction, especially in the generation of action potentials. Patch-clamp recordings revealed that I Na , I K , and I Cl were expressed early in postnatal development. However, only I K and I Cl densities increased significantly in developing Na/OUT cells.Consistent with the rise of I K density, we found that action potential waveform changed markedly, with an increased speed of repolarization that was accompanied by an enhanced capability of repetitive firing. In addition to membrane excitability changes in putative sensory cells, we observed a concomitant increase in the occurrence of glia-like taste cells (the so called "leaky" cells) among patched cells. Leaky cells are likely involved in dissipating the increase of extracellular K ϩ during action potential discharge in chemosensory cells. Thus, developing taste cells of the mouse vallate papilla undergo a significant electrophysiological maturation and diversification. These functional changes may have a profound impact on the transduction capabilities of taste buds during development.

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“…IP 3 increases [Ca 2ϩ ] i via IP 3 R3 activation (14 -16). A third mechanism involves a direct interaction and inhibition of K ϩ channels resulting in depolarization and increased [Ca 2ϩ ] i (17). The fourth known mechanism is the direct gating of nonselective cation channels and depolarization, again leading to increased [Ca 2ϩ ] i (18 -20).…”

mentioning

confidence: 99%

Stimulation of Insulin Secretion by Denatonium, One of the Most Bitter-Tasting Substances Known

et al. 2003

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Denatonium, one of the most bitter-tasting substances known, stimulated insulin secretion in clonal HIT-T15 ␤-cells and rat pancreatic islets. Stimulation of release began promptly after exposure of the ␤-cells to denatonium, reached peak rates after 4 -5 min, and then declined to near basal values after 20 -30 min. In islets, no effect was observed at 2.8 mmol/l glucose, whereas a marked stimulation was observed at 8. M ultiple signal transduction mechanisms in taste cells detect sweet, sour, bitter, salty, and umami tastes and involve both receptormediated second messenger pathways and direct interactions with ion channels (1-3). Four mechanisms have been identified for signal transduction by bitter compounds. Two mechanisms result from bitter substances interacting with receptors of the T2R/TRB family and activation of gustducin (4 -10). In one, the ␣-subunit of gustducin activates cyclic nucleotide phosphodiesterase activity to decrease cyclic nucleotide monophosphate (cyclic NMP) levels and de-inhibit the activity of a cyclic NMP-inhibited cation channel leading to depolarization and increased [Ca 2ϩ ] i (11,12). In the second, the ␤␥-subunits of gustducin (probably ␤1␥13 and/or ␤3␥13) activate PLC␤2 and increase IP 3 and DAG levels (13,14). IP 3 increases [Ca 2ϩ ] i via IP 3 R3 activation (14 -16). A third mechanism involves a direct interaction and inhibition of K ϩ channels resulting in depolarization and increased [Ca 2ϩ ] i (17). The fourth known mechanism is the direct gating of nonselective cation channels and depolarization, again leading to increased [Ca 2ϩ ] i (18 -20). In all cases, increased [Ca 2ϩ ] i leads to increased neurotransmitter release and activation of the afferent gustatory nerves that transmit the bitter signal to the brain. There is evidence for the activation of multiple second messenger pathways in individual taste cells (4). There is also evidence that some bitter stimuli activate only subpopulations of bitter-sensitive taste cells (4 -6). Also, individual taste cells can respond selectively to different bitter substances (7). However, there is still much that is unknown about individual taste cell regulation.Stimulation of taste cell membranes with denatonium activates not only gustducin but also transducin (9), with which it shares high sequence homology (21). Because transducin mRNA is reported to be present in pancreatic islets at approximately one-fifth the level of that in the retina (22), we were interested to determine the effects of denatonium on insulin secretion in ␤-cells as a tool to study the potential involvement of gustducin or transducin in stimulus-secretion coupling. The experiments described here were performed on clonal HIT-T15 cells and rat pancreatic islets. RESEARCH DESIGN AND METHODSCell culture. Clonal HIT-T15 cells were cultured in RPMI 1640 medium supplemented with 10% fetal bovine serum, 100 g/ml streptomycin, and 100 units/ml penicillin in an atmosphere of 95% air and 5% CO 2 . Cells of passage numbers 72-85 were used for the expe...

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Identification of electrophysiologically distinct subpopulations of rat taste cells

Cited by 39 publications

References 38 publications

Membrane currents in taste cells of the rat fungiform papilla. Evidence for two types of Ca currents and inhibition of K currents by saccharin.

Membrane currents in taste cells of the rat fungiform papilla. Evidence for two types of Ca currents and inhibition of K currents by saccharin.

Postnatal Development of Membrane Excitability in Taste Cells of the Mouse Vallate Papilla

Stimulation of Insulin Secretion by Denatonium, One of the Most Bitter-Tasting Substances Known

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