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

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.

scholarly journals The organization of taste sensibilities in hamster chorda tympani nerve fibers.

1988 ◽  
Vol 91 (6) ◽  
pp. 861-896 ◽  
Author(s):  
M E Frank ◽  
S L Bieber ◽  
D V Smith
Keyword(s):  
Cluster Analysis ◽  
Factor Analysis ◽  
Hierarchical Cluster Analysis ◽  
Nerve Impulse ◽  
Hierarchical Cluster ◽  
Nerve Fibers ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Activation Patterns ◽  
Response Profiles

Electrophysiological measurements of nerve impulse frequencies were used to explore the organization of taste sensibilities in single fibers of the hamster chorda tympani nerve. Moderately intense taste solutions that are either very similar or easily discriminated were applied to the anterior lingual surface. 40 response profiles or 13 stimulus activation patterns were considered variables and examined with multivariate statistical techniques. Three kinds of response profiles were seen in fibers that varied in their overall sensitivity to taste solutions. One profile (S) showed selectivity for sweeteners, a second (N) showed selectivity for sodium salts, and a third (H) showed sensitivity to salts, acids, and other compounds. Hierarchical cluster analysis indicated that profiles fell into discrete classes. Responses to many pairs of effective stimuli were covariant across profiles within a class, but some acidic stimuli had more idiosyncratic effects. Factor analysis of profiles identified two common factors, accounting for 77% of the variance. A unipolar factor was identified with the N profile, and a bipolar factor was identified with the S profile and its opposite, the H profile. Three stimulus activation patterns were elicited by taste solutions that varied in intensity of effect. Hierarchical cluster analysis indicated that the patterns fell into discrete classes. Factor analysis of patterns identified three common unipolar factors accounting for 82% of the variance. Eight stimuli (MgSO4, NH4Cl, KCl, citric acid, acetic acid, urea, quinine HCl, HCl) selectively activated fibers with H profiles, three stimuli (fructose, Na saccharin, sucrose) selectively activated fibers with S profiles, and two stimuli (NaNO3, NaCl) activated fibers with N profiles more strongly than fibers with H profiles. Stimuli that evoke different patterns taste distinct to hamsters. Stimuli that evoke the same pattern taste more similar. It was concluded that the hundreds of peripheral taste neurons that innervate the anterior tongue play one of three functional roles, providing information about one of three features that are shared by different chemical solutions.

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.

Ion transport across lingual epithelium is modulated by chorda tympani nerve fibers

1993 ◽  
Vol 615 (2) ◽  
pp. 218-228 ◽  
Author(s):  
S.A. Simon ◽  
E.J. Elliott ◽  
R.P. Erickson ◽  
V.F. Holland
Keyword(s):  
Ion Transport ◽  
Nerve Fibers ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Lingual Epithelium

Chorda Tympani Nerve Fibers in Man

1983 ◽  
Vol 95 (1-4) ◽  
pp. 291-296 ◽  
Author(s):  
Jukka Ylikoski ◽  
Roberto Gamoletti ◽  
Frank Galey
Keyword(s):  
Nerve Fibers ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve

Nerve fibers sensitive to ionic taste stimuli in chorda tympani of the rat

1983 ◽  
Vol 50 (4) ◽  
pp. 941-960 ◽  
Author(s):  
M. E. Frank ◽  
R. J. Contreras ◽  
T. P. Hettinger
Keyword(s):  
Chemical Compounds ◽  
Nerve Fibers ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Stimulus Quality ◽  
Quinine Hydrochloride ◽  
Taste Reception ◽  
The Central Nervous System ◽  
Stimuli Response ◽  
Response Profiles

Hypotheses about the peripheral basis for the sense of taste in mammals have been based to a considerable degree on the determined sensibilities of the nerve fibers in the chorda tympani of the rat to chemical stimulation of the anterior tongue. Yet, whether neuron types exist in this nerve, the nature of the basic mechanisms of taste reception that are tapped by this nerve and the form in which information about stimulus quality and intensity is transmitted to the central nervous system by this nerve are, at present, unresolved issues. These issues are addressed in the present study, which is a detailed analysis of the responses of rat chorda tympani nerve fibers that are sensitive to ionic stimuli; solutions applied to the anterior tongue included a range of concentrations of four chemical compounds (sucrose, sodium chloride, hydrochloric acid, and quinine hydrochloride) that represent widely different taste qualities to man or rat. Of the 44 nerve fibers sampled, 40 were stimulated most by one of the two ionic stimuli at test concentrations reported to be equally effective: 21 fibers were most responsive to 0.1 M NaCl and named N units; 19 fibers were most responsive to 0.01 M HCl and named H units. Although many N and H units responded to both HCl and NaCl, the distribution of NaCl-HCl response ratios was bimodal, indicating there are two varieties of units sensitive to ionic taste stimuli in the rat chorda tympani. Sucrose (0.5 M) affected 4 of the nerve fibers and was the most effective stimulus for 3 of them; 0.02 M quinine affected 13 of the fibers but 10 of these were H units. H units were less "specifically tuned" than N units; they were more likely to respond to several of the chemicals. Although the absolute sensitivity to NaCl in N units or to HCl in H units varied more than 10-fold, the relative effects of the four stimuli (response profiles) were generally similar for units of a given type. Exceptions occurred when H unit responses to NaCl or quinine were suppressed by prolonged effects of preceding HCl stimulation. The similarity in response profiles is reflected in high and significant correlations between responses to each pair of effective stimuli across either H or N units.(ABSTRACT TRUNCATED AT 400 WORDS)

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