scholarly journals Anion modulation of taste responses in sodium-sensitive neurons of the hamster chorda tympani nerve.

1993 ◽  
Vol 101 (3) ◽  
pp. 453-465 ◽  
Author(s):  
B G Rehnberg ◽  
B I MacKinnon ◽  
T P Hettinger ◽  
M E Frank
Keyword(s):  
Nerve Fibers ◽  
Na Channel ◽  
Acetate Anion ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Wide Range ◽  
Nacl Concentration ◽  
Stimulus Concentration ◽  
Taste Cells ◽  
Epithelial Membranes

Beidler's work in the 1950s showed that anions can strongly influence gustatory responses to sodium salts. We have demonstrated "anion inhibition" in the hamster by showing that the chorda tympani nerve responds more strongly to NaCl than to Na acetate over a wide range of concentrations. Iontophoretic presentation of Cl- and acetate to the anterior tongue elicited no response in the chorda tympani, suggesting that these anions are not directly stimulatory. Drugs (0.01, 1.0, and 100 microM anthracene-9-carboxylate, diphenylamine-2-carboxylate, 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonate, and furosemide) that interfere with movements of Cl- across epithelial cells were ineffective in altering chorda tympani responses to 0.03 M of either NaCl or Na acetate. Anion inhibition related to movements of anions across epithelial membranes therefore seems unlikely. The chorda tympani contains a population of nerve fibers highly selective for Na+ (N fibers) and another population sensitive to Na+ as well as other salts and acids (H fibers). We found that N fibers respond similarly to NaCl and Na acetate, with spiking activity increasing with increasing stimulus concentration (0.01-1.0 M). H fibers, however, respond more strongly to NaCl than to Na acetate. Furthermore, H fibers increase spiking with increases in NaCl concentration, but generally decrease their responses to increasing concentrations of Na acetate. It appears that anion inhibition applies to taste cells innervated by H fibers but not by N fibers. Taste cells innervated by N fibers use an apical Na+ channel, whereas those innervated by H fibers may use a paracellularly mediated, basolateral site of excitation.

scholarly journals Optogenetic Activation of Type III Taste Cells Modulates Taste Responses

2020 ◽  
Vol 45 (7) ◽  
pp. 533-539
Author(s):  
Aurelie Vandenbeuch ◽  
Courtney E Wilson ◽  
Sue C Kinnamon
Keyword(s):  
Light Response ◽  
Sensory Nerves ◽  
Taste Bud ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Type Iii ◽  
Nonspecific Effects ◽  
Taste Cells ◽  
Specific Stimulation ◽  
The Brain

Abstract Studies have suggested that communication between taste cells shapes the gustatory signal before transmission to the brain. To further explore the possibility of intragemmal signal modulation, we adopted an optogenetic approach to stimulate sour-sensitive (Type III) taste cells using mice expressing Cre recombinase under a specific Type III cell promoter, Pkd2l1 (polycystic kidney disease-2-like 1), crossed with mice expressing Cre-dependent channelrhodopsin (ChR2). The application of blue light onto the tongue allowed for the specific stimulation of Type III cells and circumvented the nonspecific effects of chemical stimulation. To understand whether taste modality information is preprocessed in the taste bud before transmission to the sensory nerves, we recorded chorda tympani nerve activity during light and/or chemical tastant application to the tongue. To assess intragemmal modulation, we compared nerve responses to various tastants with or without concurrent light-induced activation of the Type III cells. Our results show that light significantly decreased taste responses to sweet, bitter, salty, and acidic stimuli. On the contrary, the light response was not consistently affected by sweet or bitter stimuli, suggesting that activation of Type II cells does not affect nerve responses to stimuli that activate Type III cells.

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

1999 ◽  
Vol 81 (6) ◽  
pp. 3087-3091 ◽  
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.

scholarly journals Acetic acid modulates spike rate and spike latency to salt in peripheral gustatory neurons of rats

2012 ◽  
Vol 108 (9) ◽  
pp. 2405-2418 ◽  
Author(s):  
Joseph M. Breza ◽  
Robert J. Contreras
Keyword(s):  
Acetic Acid ◽  
Artificial Saliva ◽  
Type I ◽  
Dependent Manner ◽  
Chorda Tympani ◽  
Gustatory System ◽  
Chorda Tympani Nerve ◽  
Concentration Dependent Manner ◽  
Lingual Epithelium ◽  
Taste Cells

Sour and salt taste interactions are not well understood in the peripheral gustatory system. Therefore, we investigated the interaction of acetic acid and NaCl on taste processing by rat chorda tympani neurons. We recorded multi-unit responses from the severed chorda tympani nerve (CT) and single-cell responses from intact narrowly tuned and broadly tuned salt-sensitive neurons in the geniculate ganglion simultaneously with stimulus-evoked summated potentials to signal when the stimulus contacted the lingual epithelium. Artificial saliva served as the rinse and solvent for all stimuli [0.3 M NH4Cl, 0.5 M sucrose, 0.1 M NaCl, 0.01 M citric acid, 0.02 M quinine hydrochloride (QHCl), 0.1 M KCl, 0.003–0.1 M acetic acid, and 0.003–0.1 M acetic acid mixed with 0.1 M NaCl]. We used benzamil to assess NaCl responses mediated by the epithelial sodium channel (ENaC). The CT nerve responses to acetic acid/NaCl mixtures were less than those predicted by summing the component responses. Single-unit analyses revealed that acetic acid activated acid-generalist neurons exclusively in a concentration-dependent manner: increasing acid concentration increased response frequency and decreased response latency in a parallel fashion. Acetic acid suppressed NaCl responses in ENaC-dependent NaCl-specialist neurons, whereas acetic acid-NaCl mixtures were additive in acid-generalist neurons. These data suggest that acetic acid attenuates sodium responses in ENaC-expressing-taste cells in contact with NaCl-specialist neurons, whereas acetic acid-NaCl mixtures activate distinct receptor/cellular mechanisms on taste cells in contact with acid-generalist neurons. We speculate that NaCl-specialist neurons are in contact with type I cells, whereas acid-generalist neurons are in contact with type III cells in fungiform taste buds.

scholarly journals Effects of voltage perturbation of the lingual receptive field on chorda tympani responses to Na+ and K+ salts in the rat: implications for gustatory transduction.

1994 ◽  
Vol 104 (5) ◽  
pp. 885-907 ◽  
Author(s):  
Q Ye ◽  
G L Heck ◽  
J A DeSimone
Keyword(s):  
Receptive Field ◽  
Voltage Clamp ◽  
Maximal Response ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Salt Taste ◽  
Negative Voltage ◽  
Voltage Clamp Condition ◽  
Taste Cells ◽  
Clamp Condition

Taste sensory responses from the chorda tympani nerve of the rat were recorded with the lingual receptive field under current or voltage clamp. Consistent with previous results (Ye, Q., G. L. Heck, and J. A. DeSimone. 1993. Journal of Neurophysiology. 70:167-178), responses to NaCl were highly sensitive to lingual voltage clamp condition. This can be attributed to changes in the electrochemical driving force for Na+ ions through apical membrane transducer channels in taste cells. In contrast, responses to KCl over the concentration range 50-500 mM were insensitive to the voltage clamp condition of the receptive field. These results indicate the absence of K+ conductances comparable to those for Na+ in the apical membranes of taste cells. This was supported by the strong anion dependence of K salt responses. At zero current clamp, the potassium gluconate (KGlu) threshold was > 250 mM, and onset kinetics were slow (12 s to reach half-maximal response). Faster onset kinetics and larger responses to KGlu occurred at negative voltage clamp (-50 mV). This indicates that when K+ ion is transported as a current, and thereby uncoupled from gluconate mobility, its rate of delivery to the K+ taste transducer increases. Analysis of conductances shows that the paracellular pathway in the lingual epithelium is 28 times more permeable to KCl than to KGlu. Responses to KGlu under negative voltage clamp were not affected by agents that are K+ channel blockers in other systems. The results indicate that K salt taste transduction is under paracellular diffusion control, which limits chemoreception efficiency. We conclude that rat K salt taste occurs by means of a subtight junctional transducer for K+ ions with access limited by anion mobility. The data suggest that this transducer is not cation selective which also accounts for the voltage and amiloride insensitive part of the response to NaCl.

scholarly journals Capsaicin Modifies Responses of Rat Chorda Tympani Nerve Fibers to NaCl

1997 ◽  
Vol 22 (3) ◽  
pp. 249-255 ◽  
Author(s):  
Kazumi Osada ◽  
Michio Komai ◽  
Bruce P. Bryant ◽  
Hitoshi Suzuki ◽  
Atsuko Goto ◽  
...  
Keyword(s):  
Nerve Fibers ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve

Taste Responsiveness of Fungiform Taste Cells With Action Potentials

2006 ◽  
Vol 96 (6) ◽  
pp. 3088-3095 ◽  
Author(s):  
Ryusuke Yoshida ◽  
Noriatsu Shigemura ◽  
Keisuke Sanematsu ◽  
Keiko Yasumatsu ◽  
Satoru Ishizuka ◽  
...  
Keyword(s):  
Action Potentials ◽  
Basolateral Membrane ◽  
Extracellular Recording ◽  
Hierarchical Cluster ◽  
Nerve Fibers ◽  
Chorda Tympani ◽  
Cell Responses ◽  
Single Receptor ◽  
Gustatory Nerve ◽  
Taste Cells

It is known that a subset of taste cells generate action potentials in response to taste stimuli. However, responsiveness of these cells to particular tastants remains unknown. In the present study, by using a newly developed extracellular recording technique, we recorded action potentials from the basolateral membrane of single receptor cells in response to taste stimuli applied apically to taste buds isolated from mouse fungiform papillae. By this method, we examined taste-cell responses to stimuli representing the four basic taste qualities (NaCl, Na saccharin, HCl, and quinine-HCl). Of 72 cells responding to taste stimuli, 48 (67%) responded to one, 22 (30%) to two, and 2 (3%) to three of four taste stimuli. The entropy value presenting the breadth of responsiveness was 0.158 ± 0.234 (mean ± SD), which was close to that for the nerve fibers (0.183 ± 0.262). In addition, the proportion of taste cells predominantly sensitive to each of the four taste stimuli, and the grouping of taste cells based on hierarchical cluster analysis, were comparable with those of chorda tympani (CT) fibers. The occurrence of each class of taste cells with different taste responsiveness to the four taste stimuli was not significantly different from that of CT fibers except for classes with broad taste responsiveness. These results suggest that information derived from taste cells generating action potentials may provide the major component of taste information that is transmitted to gustatory nerve fibers.

Amiloride Blocks Acid Responses in NaCl-Best Gustatory Neurons of the Hamster Solitary Nucleus

1998 ◽  
Vol 80 (3) ◽  
pp. 1362-1372 ◽  
Author(s):  
John D. Boughter ◽  
David V. Smith
Keyword(s):  
Citric Acid ◽  
Taste Receptor ◽  
Nerve Fibers ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Receptor Cells ◽  
Biophysical Studies ◽  
Taste Receptor Cells ◽  
To Receive ◽  
Gustatory Neurons

Boughter, John D., Jr. and David V. Smith. Amiloride blocks acid responses in NaCl-best gustatory neurons of the hamster solitary nucleus. J. Neurophysiol. 80: 1362–1372, 1998. Biophysical studies of isolated taste receptor cells show that one mechanism of Na+ salt transduction involves the inward movement of Na+ through amiloride-blockable ion channels on the apical receptor cell membrane, which leads to a direct depolarization. Hamster taste receptor cells with amiloride-blockable Na+ responses also show an amiloride-sensitive H+ current. Thus one mechanism for the transduction of acid taste involves the amiloride-sensitive channel. We investigated the effects of amiloride on responses to acids in neurons of the nucleus of the solitary tract (NST) of the hamster. The responses of 47 NST neurons were recorded extracellularly while the anterior tongue was stimulated with solutions representing the four taste qualities (NaCl, sucrose, HCl, quinine), which were used to characterize each cell on the basis of its best stimulus. The effects of amiloride on responses to 10 mM HCl, 10 mM citric acid, 100 mM NaCl, and 100 mM sucrose were then investigated. Stimuli were presented alone for 30 s (control trials) and also presented for 10 s, followed by a mixture of the stimulus with 10 μM amiloride for 10 s, followed by the stimulus alone again for 10 s (amiloride trials). The effects of amiloride were assessed by comparing the responses of cells with the stimulus + amiloride with that of the stimulus alone. In neurons classified as NaCl-best, amiloride reversibly blocked responses to NaCl, HCl, and citric acid. In HCl-best neurons, amiloride had no effect on responses to any of these stimuli. In sucrose-best neurons, amiloride blocked the response to NaCl but not to sucrose or to either acid. These results support the hypothesis that acids are transduced by at least two different receptor mechanisms in the hamster, amiloride sensitive and amiloride insensitive. At the NST, these inputs are tightly maintained in two separate populations of neurons. Sucrose-best neurons, which show amiloride effects on NaCl but not acids, appear to receive converging inputs from both amiloride-sensitive (N-best) and amiloride-insensitive (H-best) chorda tympani nerve fibers.

Enhancement of gustatory nerve fibers to NaCl and formation of ion channels by commercial novobiocin

1994 ◽  
Vol 266 (5) ◽  
pp. C1165-C1172 ◽  
Author(s):  
A. M. Feigin ◽  
Y. Ninomiya ◽  
S. M. Bezrukov ◽  
B. P. Bryant ◽  
P. A. Moore ◽  
...  
Keyword(s):  
Ion Channels ◽  
Lipid Bilayers ◽  
Neutral Lipids ◽  
Nerve Fibers ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Salt Taste ◽  
Cation Selectivity ◽  
Taste Response ◽  
Gustatory Nerve

Single fibers of the rat chorda tympani nerve were used to study the mechanism of action of the antibiotic novobiocin on salt taste transduction. In the rat, novobiocin selectively enhanced the responses of sodium-specific and amiloride-sensitive chorda tympani nerve fibers (N type) without affecting more broadly responsive cation-sensitive and amiloride-insensitive fibers (E type). In the presence of amiloride, novobiocin was ineffective at enhancing the response of N-type fibers toward sodium chloride. Novobiocin also increased the conductance of bilayers formed from neutral lipids by forming nonrectifying ion channels with low conductance (approximately 7 pS in 110 mM NaCl), long open times (several seconds and longer), and high cation selectivity. Amiloride did not alter either the conductance or kinetics of these novobiocin channels. These observations suggest that even though novobiocin is able to form cation channels in lipid bilayers, and possibly in cell membranes as well, its action on the salt-taste response is through modulation of existing amiloride-sensitive sodium channels.

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