scholarly journals Neurophysiological and biophysical evidence on the mechanism of electric taste.

1985 ◽  
Vol 86 (1) ◽  
pp. 59-87 ◽  
Author(s):  
M S Herness
Keyword(s):  
Iodoacetic Acid ◽  
Transport Numbers ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Lingual Epithelium ◽  
Ion Migration ◽  
Before And After ◽  
Accumulation Mechanism ◽  
Current Densities ◽  
Electric Taste

The phenomenon of electric taste was investigated by recording from the chorda tympani nerve of the rat in response to both electrical and chemical stimulations of the tongue with electrolytes in order to gain some insight into its mechanism on both a neurophysiological and biophysical basis. The maximum neural response levels were identical for an individual salt (LiCl, NaCl, KCl, or CaCl2), whether it was presented as a chemical solution or as an anodal stimulus through a subthreshold solution. These observations support the idea that stimulation occurs by iontophoresis of ions to the receptors at these current densities (less than 100 microA/cm2). Electric responses through dilute HCl were smaller than the chemically applied stimulations, but the integrated anodal responses appeared similar to chemical acid responses, as evidenced by an OFF response to both forms of stimuli. Hydrogen may be more permeant to the lingual epithelium and would thus be shunted away from the taste receptors during anodal stimulation. When the anion of electric taste was varied via subthreshold salt solutions, the response magnitude increased as the mobility of the anion decreased. The transport numbers of the salts involved adequately explains these differences. The physical aspects of ion migration occurring within the adapting fluid on the tongue are also discussed. Direct neural stimulation by the current appears to occur only at higher current densities (greater than 300 microA/cm2). If the taste cells of the tongue were inactivated with either iodoacetic acid (IAA) or N-ethyl maleimide (NEM), or removed with collagenase, then responses from the chorda tympani could be obtained only at these higher current densities. Latency measurements before and after IAA or NEM treatment corroborated these findings. The results are discussed in terms of several proposed mechanisms of electric taste and it is concluded that an ion accumulation mechanism can adequately explain the data.

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.

Gustatory changes in patients with chronic otitis media, before and after middle-ear surgery

2012 ◽  
Vol 126 (5) ◽  
pp. 470-474 ◽  
Author(s):  
C-C Huang ◽  
C-D Lin ◽  
C-Y Wang ◽  
J-H Chen ◽  
Y-T Shiao ◽  
...  
Keyword(s):  
Otitis Media ◽  
Middle Ear ◽  
Chronic Otitis Media ◽  
Middle Ear Surgery ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Ear Surgery ◽  
Taste Testing ◽  
Gustatory Function ◽  
Before And After

AbstractObjective:We investigated gustatory changes in patients with chronic otitis media, before and after middle-ear surgery.Methods:This prospective study included 38 patients with unilateral chronic otitis media. We used taste testing solutions to evaluate each patient's taste function. Intra-operative assessments of the chorda tympani nerve were also compared and analysed.Results:Patients with chronic otitis media had significantly worse ipsilateral perception of sour, bitter and salty tastes. In patients with good intra-operative preservation of the chorda tympani nerve, there was significant improvement in gustatory function one month post-operatively, compared with the pre-operative baseline. In patients who sustained intra-operative chorda tympani nerve injury, one month post-operative gustatory function was the same as the pre-operative baseline.Conclusion:Middle-ear surgery for chronic otitis media not only treats the ear but also improves gustatory function in the majority of patients. In patients with intra-operative injury to the chorda tympani nerve, post-operative taste decline is only temporary.

Chemospecific deficits in taste detection after selective gustatory deafferentation in rats

1990 ◽  
Vol 258 (3) ◽  
pp. R820-R826 ◽  
Author(s):  
A. C. Spector ◽  
G. J. Schwartz ◽  
H. J. Grill
Keyword(s):  
Detection Threshold ◽  
Conditioned Avoidance ◽  
Taste Bud ◽  
Taste Receptors ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Before And After ◽  
The Mean ◽  
Taste Detection ◽  
Response To Water

Electrophysiological data support the existence of sodium-specific taste receptors that appear to be limited to the anterior tongue. However, previous behavioral findings suggest that bilateral transection of the chorda tympani nerve (CTn) has minimal consequences on NaCl intake and preference. This study employed a conditioned avoidance procedure to measure detection thresholds to NaCl and sucrose both before and after bilateral transection of the CTn. Rats were trained to maintain spout contact in response to water presentations (70 microliters) and to avoid spout contact when a taste solution (70 microliters) was presented. In experiment 1, all rats (n = 3) showed statistically significant impairments in the detectability of NaCl after bilateral section of the CTn. The mean increase in the NaCl detection threshold was 1.41 log units. In contrast, sucrose threshold in these same rats was marginally affected by CTn section (mean increase = 0.22 log units). Experiment 2 (n = 4) replicated the findings of the first experiment. The mean increase in the NaCl detection threshold was 2.23 log units. Sucrose threshold in these rats was, again, only marginally affected by CTn section (mean increase = 0.83 log units). Histological examination of the anterior tongue from the rats in experiment 2 indicated that the CTn transections were complete. These findings reveal that the anterior oral receptive field (innervated by the CTn) containing only 15% of the total taste bud population is critical for the normal detection of NaCl.

Gurmarin inhibition of sweet taste responses in mice

1995 ◽  
Vol 268 (4) ◽  
pp. R1019-R1025 ◽  
Author(s):  
Y. Ninomiya ◽  
T. Imoto
Keyword(s):  
Sweet Taste ◽  
Suppressive Effect ◽  
Taste Receptors ◽  
Gymnema Sylvestre ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Inhibitory Effects ◽  
Sweet Taste Receptors ◽  
Before And After ◽  
C57bl Mice

The inhibitory effects of gurmarin (a peptide isolated from the leaves of Gymnema sylvestre) on sweet taste responses were studied by examining the chorda tympani nerve responses to various taste substances before and after lingual treatment with gurmarin in C57BL and BALB mice. Treatment with gurmarin at 3 micrograms/ml or more selectively suppressed responses to sucrose without affecting responses to NaCl, HCl, and quinine in C57BL mice, whereas gurmarin at 100 micrograms/ml did not significantly suppress sucrose responses in BALB mice. Responses to various sweet substances in C57BL mice decreased to approximately 45-75% of control after gurmarin, and the suppressive effect of gurmarin was reversible. The profile of the residual responses of C57BL mice to various sweeteners after gurmarin was almost identical to that of BALB mice, which was hardly affected by gurmarin. These results strongly suggest that there are at least two types of sweet taste receptors in mice, gurmarin-sensitive and -insensitive. Probably, C57BL and BALB mice share an identical gurmarin-insensitive receptor, and C57BL mice also have a gurmarin-sensitive receptor.

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

scholarly journals Endoscopic Ossiculoplasty for the Management of Isolated Congenital Ossicular Chain Malformation: Surgical Results in 16 Ears

2020 ◽  
pp. 014556132093121
Author(s):  
Chunlin Zhang ◽  
Jiaoping Mi ◽  
Dan Long ◽  
Yuan Deng ◽  
Qiang Sun ◽  
...  
Keyword(s):  
Bone Conduction ◽  
Ossicular Chain ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Hearing Outcome ◽  
Before And After ◽  
Ossicular Replacement ◽  
The Mean ◽  
Replacement Prosthesis ◽  
Air Conduction

Objective: The aim of this study is to describe the clinical characteristics and intraoperative findings and further evaluate the efficacy of endoscopic ossiculoplasty for the management of isolated congenital ossicular chain malformation. Methods: A retrospective study was performed on 16 ears (15 patients) with the isolated congenital ossicular chain malformation who underwent endoscopic ossiculoplasty in our department from May 2017 to January 2019. Endoscopic exploratory tympanotomy was conducted to check the ossicular chain; at the same time, endoscopic ossiculoplasty was performed depending on intraoperative findings. Air-conduction thresholds, bone-conduction thresholds, and air-bone gaps (ABGs) were measured before and after surgery, and the hearing outcome was assessed at 6 months postoperatively. Results: The most common malformations of ossicular chain were the missing of the incus long process and stapes suprastructure. A serial assessment of the hearing status was conducted before and 6 months after surgery. It showed the mean postoperative pure-tone average (PTA) was significantly reduced, and the mean postoperative ABG was obviously closed, respectively ( P < .001). The mean PTA gain was 36.3 ± 8.6 dB, and the ABG closure was 35.1 ± 8.3 dB; ABG closure to 20 dB or less and ABG closure to 10 dB or less were achieved in 14 cases (87.5%) and 5 cases (31.3%), respectively. No differences were observed in postoperative hearing outcome between type Ⅲ cases and type Ⅳ cases; however, cases with partial ossicular replacement prosthesis implantation showed a larger hearing gain ( P = .049) and a higher proportion of postoperative ABG less than 10 dB ( P = .021). No facial palsy and significant sensorineural hearing loss occurred; all patients completed the surgery without the need of canalplasty, and the chorda tympani nerve was preserved in all patients. Conclusions: This research showed endoscopic surgery was effective in the diagnosis and management of isolated congenital ossicular chain malformation; the endoscopic ossiculoplasty provides an alternative method to manage congenital ossicular chain malformation, with comfortable hearing outcome and the advantage of excellent vision and less invasion.

Effect of Amiloride on Gustatory Responses in the Ventroposteromedial Nucleus of the Thalamus in Rats

2005 ◽  
Vol 93 (1) ◽  
pp. 157-166 ◽  
Author(s):  
Justus V. Verhagen ◽  
Barbara K. Giza ◽  
Thomas R. Scott
Keyword(s):  
Channel Blocker ◽  
Lithium Salts ◽  
Chorda Tympani ◽  
Solitary Tract ◽  
Chorda Tympani Nerve ◽  
Sodium Channel Blocker ◽  
Oral Application ◽  
Response Profile ◽  
Before And After ◽  
Ventroposteromedial Nucleus

The existence of gustatory neuron types has been demonstrated in the chorda tympani nerve and the nucleus of the solitary tract (NTS) of rats and hamsters through the oral application of amiloride, a sodium channel blocker. At these lower-order levels, amiloride was shown to reduce the response to sodium and lithium salts in sodium- and sugar-oriented cells, while leaving those of acid- and quinine-oriented neurons unmodified. We extended this investigation to higher-order levels by determining whether amiloride suppressed the responses of cells at the 4th-order gustatory relay in the thalamus, which neurons were affected, the degree of suppression, and whether the subsequent neural code for sodium was altered. We stimulated the whole oral cavity of anesthetized rats with a variety of tastants while recording the responses of 42 single thalamic neurons before and after the application of amiloride. The results revealed a similar pattern to that reported in the NTS. Amiloride inhibited only sodium- and sugar-oriented neurons, and specifically their responses to sodium- or lithium-containing stimuli. Moreover, there was a significant relationship between the degree of sodium specificity of a neuron and its sensitivity to inhibition by amiloride. These results demonstrate a relationship between a cell's response profile and its susceptibility to amiloride, and so offer evidence that gustatory neuron types exist through the level of the thalamus in rats. Thus membership in a neuronal group retains functional significance based on a receptor event 4 synapses away.

Spatial map of salts and saccharides on dog tongue

1988 ◽  
Vol 255 (1) ◽  
pp. R117-R122
Author(s):  
J. L. Garvin ◽  
R. Robb ◽  
S. A. Simon
Keyword(s):  
Spatial Heterogeneity ◽  
Open Circuit Potential ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Lingual Epithelium ◽  
Ussing Chambers ◽  
Chloride Salts

Front and rear regions of dog tongue were tested for spatial heterogeneity with respect to monovalent chloride salts (NaCl, KCl, and NH4Cl) and sweet tastants (sucrose, D-glucose, and L-glucose) by placing them in Ussing chambers where the open-circuit potential, Voc, and short-circuit current, Isc, were measured. The responses of Voc and Isc to 0.5 M NaCl were greater in the front of the tongue than in the rear, whereas the responses of Voc and Isc to 0.5 M sucrose were greater in the rear of the tongue than in the front. These results are similar to those of published neurophysiological measurements from the chorda tympani nerve and thalamus. These data suggest that the spatial heterogeneities seen in higher taste centers are present in the isolated lingual epithelium where primary taste transduction events occur.

An analysis of residual NaCl taste response after amiloride

1988 ◽  
Vol 255 (6) ◽  
pp. R1002-R1007 ◽  
Author(s):  
B. K. Formaker ◽  
D. L. Hill
Keyword(s):  
Choline Chloride ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Sodium Salts ◽  
Original Response ◽  
Taste Response ◽  
Electrophysiological Recordings ◽  
Cross Adaptation ◽  
Before And After ◽  
Residual Response

The identity of the residual taste response to NaCl after lingual application of the sodium transport blocker, amiloride, was studied by electrophysiological recordings from the rat chorda tympani nerve. Stimulation of the anterior tongue with salt solutions resulted in responses to halogenated sodium salts that were not eliminated by amiloride; approximately 30% of the halogenated sodium salt response remained after amiloride. In contrast, responses to nonhalogenated sodium salts were reduced to less than 4% of the original response after amiloride. To further learn of characteristics relating to the residual NaCl response, binary mixture and cross-adaptation experiments were accomplished. Responses to mixtures of sodium acetate or sodium bicarbonate with choline chloride were similar to responses elicited by equimolar concentrations of NaCl before and after amiloride. Moreover, NaCl and NaBr cross-adapted with choline chloride after, but not before, lingual application of amiloride. These experiments indicate that the residual response to halogenated sodium salts (e.g., NaCl) is related to the halogen itself, and from findings presented here, we propose one pathway for sodium taste transduction.

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