Chorda tympani

A century ago, Fick proposed the concept of four primary tastes, namely, sweet, salty, sour, and bitter. It has since been found that taste sensations are not describable by a single collection of discrete primaries. Electrophysiological studies of afierent taste-units in the chorda tympani and glossophyrangeal nerves have revealed that a continuous spectrum of gustation may be based on these four taste elements. Furthermore, the intensities of the tastes that we commonly experience are due not only to gustatory sensations but also to tactile, hot and cold, and, above all, olfactory sensations. The complexities of taste studies are such that, unless one of the taste modalities is singled out for study, there is very little hope of success. 

Another clinically important effect I would like to mention is the inhibition of salivary secretion by clonidine. Both the sympathetic nervous system and the parasympathetic nervous system are involved in the physiological regulation of salivation. HOEFKE (53) as well as RAND and coworkers (54) found that parasympathetic salivary secretion stimulated by electrical impulses on the chorda tympani and by carbachol could not be blocked by clonidine in anaesthetised animals. In our own experiments in rats with clonidine and the 2,6-diethyl derivative St 91 which does not penetrate to the CNS, secretion of saliva was blocked only after clonidine, (HOEFKE (55)) indicating a central mode of action. 

Figure 2. Integrated neural discharge from the gerbil s chorda tympani nerve in response to a series of increasing concentrations of sucrose applied to the tongue. The solid bars under the records indicate stimulus duration, R is the measure of...

Figure 4. Mean integrated response of the chorda tympani nerve discharge in the gerbil to sucrose (A), methyl a-o-glucopyranoside (A), methyl (S-o-glucopy-ranoside ( ), methyl f -o-fructofuranoside ( ), methyl a-o-fructofuranoside (O), methyl a-o-fructopyranoside ( ), methyl p-n-fructopyranoside (Y), 1,5-anhydro-o-mannitol (Q), fructose (equilibrium mixture, 25°C) (V) Responses are relative to the maximum sucrose response.

Figure 7. (A) Comparison of integrated chorda tympani nerve responses to methyl a-n-glucopyranoside (0)N — 15, methyl a-D-xylopyranoside (A) N — 5, and methyl 2-deoxy-a-D-arabino-hexopy-ranoside ( ) N = 5 solutions flowed over the tongue. Bars represent 95% confidence intervals. (B) Taste responses to methul a-D-glucopyranoside (0) N — 15, methyl a-v-mannopyranoside (O) N = 6, ana methyl a-D-galactopyranoside (A) N = 5. Responses relative to sucrose response of 100% (13).

G. Hellekant, V. Danilova, Y. Ninomiya. Primate sense of taste behavioral and single chorda tympani and glossopharyngeal nerve fiber recordings in the rhesus monkey, Macaca mulatto. J Neuropihysial, Tl (2), 978-993, 1997. 

Brand JG, Teeter JH, Silver WL. Inhibition by amiloride of chorda tympani responses evoked by monovalent salts. Brain Res. 1985 334 207-214. 

Shigemura N, Islam AA, Sadamitsu C, Yoshida R, Yasumatsu K, Ninomiya Y. Expression of amiloride-sensitive epithelial sodium channels in mouse taste cells after chorda tympani nerve crush. Chem. Senses 2005 30 531-538. 

DeSimone JA, Lyall V, Heck GL, Phan TH, Alam RI, Feldman GM, Buch RM. A novel pharmacological probe links the amiloride-insensitive NaCl, KCl, and NH(4)C1 chorda tympani taste responses. J. Neurophysiol. 2001 86 2638-2641. 

Ogiso K, Shimizu Y, Watanabe K, Tonosaki K. Possible involvement of undissociated acid molecules in the acid response of the chorda tympani nerve of the rat. J. Neurophysiol. 2000 83 2776— 2779. 

Its influence on the secretion of the submaxillary glands has been fully worked out. This gland receives branches from the chorda tympani nerve which is endowed with two sets of fibres, one acting immediately on the cells, the other causing the blood-vessels to dilate, being vaso-lnhlbltory. 

The author postulated this to be due to block of the chorda tympani, which runs with cranial nerve VII close to the site of the Nadbath Rehman block. 

Danilova V, Hellekant G (2003) Comparison of the responses of the chorda tympani and glossopharyngeal nerves to taste stimuli in C57BL/6J mice. BMC Neurosci 4 5 Dellisanti CD, Yao Y, Stroud JC, Wang ZZ, Chen L (2007) Crystal structure of the extracellular domain of nAChR alpha 1 bound to alpha-bungarotoxin at 1.94 A resolution. Nat Neurosci 10 953-962... 

Frank ME, Blizard DA (1999) Chorda tympani responses in two inbred strains of mice with different taste preferences. Physiol Behav 67 287-297 Fuller JL (1974) single-locus control of saccharin preference in mice. J Heredity 65 33-36 Galindo-Cuspinera V, Winnig M, Bufe B, Meyerhof W, Breslin PA (2006) A TAS1R receptor-based explanation of sweet water-taste . Nature 441 354-357 Glaser D, Tinti JM, Nofre C (1995) Evolution of the sweetness receptor in primates. I. Why does alitame taste sweet in all prosimians and simians, and aspartame only in Old World simians Chem Senses 20 573-584... 

Abbreviations CT, Chorda tympani CTX, Bilateral transection of the chorda tympani nerve DRK, Delayed-rectifying potassium FFA, Free fatty acid GL, Glossopharyngeal GLX, Bilateral transection of the glossopharyngeal nerve GPCR, G-protein-coupled receptor LCFA, Long-chain fatty acid PROP, 6-n-Propylthiouracil PTK, Protein tyrosine kinase PUFA, Polyunsaturated fatty acid NST, Nucleus of the solitary tract TG, Triglyceride TRC, Taste receptor cells TRPM5, Transient receptor potential protein 5... 

TRC from fungiform papillae and some of the anterior foliate papillae establish synaptic contacts with the chorda tympani (CT) nerve, whereas the posterior parts of the foliate and circumvallate papillae are innervated by the glossopharyngeal (GL) nerve. The possible involvement of gustatory nerves in the LCFA-mediated fat preference has recently been explored in rodents, by studying the impact of bilateral transection of the CT nerve (CTX) and/or bilateral transection of the GL nerve (GLX). 

Oquendo P, Hundt E, Lawler J, Seed B (1989) CD36 directly mediates cytoadherence of Plasmodium falciparum parasitized erythrocytes. Cell 58 95-101 Pittman DW, Labban CE, Anderson AA, O Connor HE (2006) Linoleic and oleic acids alter the licking responses to sweet, salt, sour, and bitter tastants in rats. Chem Senses 31 835-843 Pittman D, Crawley ME, Corbin CH, Smith KR (2007) Chorda tympani nerve transection impairs the gustatory detection of free fatty acids in male and female rats. Brain Res 1151 74-83... 

Stratford JM, Curtis KS, Contreras RJ (2006) Chorda tympani nerve transection alters linoleic acid taste discrimination by male and female rats. Physiol Behav 89 311-319... 

Frank ME, Bieber SL, Smith DV. 1988. The organization of taste sensibilities in hamster chorda tympani nerve fibers. J Gen Physiol 91 861-896. 

Moreno, L., Cartas, R., Merkogi, A., Alegret, S., Leija, L., Hernandez, P.R., Munoz, R. Application of the wavelet transform coupled with artificial neural networks for quantification purposes in a voltammetric electronic tongue. Sens. Actuators B 113, 487 99 (2006) Ogawa, H., Sato, M., Yamashita, S. Multiple sensitivity of chorda tympani fibres of the rat and hamster to gustatory and thermal stimuli. J. Physiol 199, 223-240 (1968)... 

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