Functional status of the regenerated chorda tympani  nerve as assessed in a salt taste discrimination task

Kopka, Stacy L.; Geran, Laura C.; Spector, Alan C.

doi:10.1152/ajpregu.2000.278.3.r720

Cited by 43 publications

(67 citation statements)

References 67 publications

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“…The morphology of fungiform papillae undergoes a stage after denervation wherein the dorsal epithelium of the papillae become more heavily keratinized, making the pore, indentation, and hillock indistinguishable from the rim of the papillae (Parks and Whitehead, 1998). Once reinnervation occurs, there is up to 90% recovery of the typical structural features characteristic of papillae with a taste bud (St. John et al, 1995;Kopka et al, 2000). The reinnervation process starts to occur as quickly as 2-3 weeks following transection and continues for at least another 3-4 weeks.…”

Section: Discussionmentioning

confidence: 99%

“…In some instances, papillae become heavily keratinized and form a spike-shaped protrusion that resembles large filiform papillae and thus are termed ''filiform-like'' (Hård af Segerstad et al, 1989;Oakley et al, 1990;Nagato et al, 1995;Sollars et al, 2002). However, when transection is performed in the adult rat, the majority of taste buds regenerate upon reinnervation by the CT, approximately 40 days following transection (St. John et al, 1995;Kopka et al, 2000). Reinnervated fungiform papillae structurally modify to resemble the predenervated morphology (Montavon et al, 1996).…”

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Chorda tympani nerve transection at different developmental ages produces differential effects on taste bud volume and papillae morphology in the rat

Sollars

2005

J. Neurobiol.

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Chorda tympani nerve transection (CTX) results in morphological changes to fungiform papillae and associated taste buds. When transection occurs during neonatal development in the rat, the effects on fungiform taste bud and papillae structure are markedly more severe than observed following a comparable surgery in the adult rat. The present study examined the potential "sensitive period" for morphological modifications to tongue epithelium following CTX. Rats received unilateral transection at 65, 30, 25, 20, 15, 10, or 5 days of age. With each descending age at the time of transection, the effects on the structural integrity of fungiform papillae were more severe. Significant losses in total number of taste buds and filiform-like papillae were observed when transection occurred 5-30 days of age. Significant reduction in the number of taste pores was indicated at every age of transection. Another group of rats received chorda tympani transection at 10, 25, or 65 days of age to determine if the time course of taste bud degeneration differed depending on the age of the rat at the time of transection. Taste bud volumes differed significantly from intact sides of the tongue at 2, 8, and 50 days post-transection after CTX at 65 days of age. Volume measurements did not differ 2 days post-transection after CTX at 10 or 25 days of age, but were significantly reduced at the other time points. Findings demonstrate a transitional period throughout development wherein fungiform papillae are highly dependent upon the chorda tympani for maintenance of morphological integrity.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Chorda tympani nerve transection at different developmental ages produces differential effects on taste bud volume and papillae morphology in the rat

Sollars

2005

J. Neurobiol.

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“…18,33). This is evident both in discrimination studies, where adulteration of the taste solutions with amiloride reduces the ability of rats to discriminate NaCl from KCl salt to chance levels (21,33), as well as in taste-aversion conditioning studies, where lingual application with amiloride causes rats to generalize between NaCl and nonsodium salts (18). Moreover, the expression of a sodium appetite, the phenomenon in which sodium-depleted rats specifically seek out and ingest sodium salts, is markedly attenuated by the adulteration of the salt solutions with amiloride (2,4,15,24,29).…”

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confidence: 94%

Taste discrimination between NaCl and KCl is disrupted by amiloride in inbred mice with amiloride-insensitive chorda tympani nerves

Eylam¹,

Spector²

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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Eylam, Shachar, and Alan C. Spector. Taste discrimination between NaCl and KCl is disrupted by amiloride in inbred mice with amiloride-insensitive chorda tympani nerves. Am J Physiol Regul Integr Comp Physiol 288: R1361-R1368, 2005 doi:10.1152/ajpregu.00796.2004.-The amiloride-sensitive salt transduction pathway is thought to be critical for the discrimination between sodium and nonsodium salts in rodents. In rats, lingual application of amiloride appears to render NaCl qualitatively indistinguishable from KCl. In this study, we tested four strains of mice for salt discriminability. In one strain (C57BL/6J), chorda tympani nerve (CT) responses to NaCl are attenuated by amiloride, and in the other three strains (BALB/cByJ, 129P3/J, DBA/2J) they are not. Under water-restriction conditions, these mice (7 mice/strain) were trained in a gustometer to lick for water from one reinforcement spout in response to a five-lick presentation of NaCl and to lick from another in response to KCl [salt concentration was varied (0.1-1 M) to render intensity irrelevant]. Mice were then tested with the stimuli dissolved in amiloride hydrochloride, and the latter was used as the reinforcer as well. Each concentration of amiloride (0.1-100 M) was used on 2 separate days with control sessions interposed. Mice from all four strains were able to discriminate NaCl from KCl reliably. Amiloride impaired this discrimination in a dose-dependent fashion. Moreover, performance on NaCl trials appeared to be more affected by amiloride than that on KCl trials in all four strains. Thus, in contrast to the predictions based on CT recordings, discrimination in all four strains appeared to depend on the amiloride-sensitive transduction pathway, which, in the case of BALB/cByJ, 129P3/J, and DBA/2J (and perhaps C57BL/6 as well), may exist in taste buds innervated by nerves other than the CT. animal psychophysics; taste transduction; taste coding; C57BL/6; BALB/c; 129P3/J; DBA/2 THE TASTE OF SODIUM CHLORIDE appears to be transduced via at least two mechanisms, one which is selective for Na ϩ (and Li ϩ ) and is disrupted by the lingual application of the epithelial Na ϩ channel-blocker amiloride (e.g., Refs. 1,3,5,8,12,16,27, 39), and the other(s) which is amiloride-insensitive and cation nonselective (e.g., 12,17,20,22,30,[35][36][37]. In rats, electrophysiological recordings from the chorda tympani (CT) nerve have demonstrated that, when amiloride is applied to the lingual epithelium, the responsiveness of this nerve to sodium salts, but not to nonsodium salts, is markedly suppressed (e.g., Refs. 3,8,12,16,27,36).Evidence supporting the importance of the amiloride-sensitive mechanism to sodium-specific taste comes from behavioral studies. Amiloride appears to render NaCl qualitatively indistinguishable from KCl in a dose-dependent fashion (e.g., Ref. 18,33). This is evident both in discrimination studies, where adulteration of the taste solutions with amiloride reduces the ability of rats to discriminate NaCl from KCl salt to chance levels (21, 33), a...

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“…Taste buds in these areas are innervated by cranial nerve VII, which critically mediates behavioral discriminations among taste stimuli in rats (Spector and Grill, 1992;Spector et al, 1997;St. John and Spector, 1998;Kopka et al, 2000;Geran et al, 2002). Neural responses to four stimuli were considered (in M): 0.5 sucrose, 0.1 NaCl, 0.01 HCl, and 0.01 quinine-HCl, respectively categorized as sweet, salty, sour, or bitter by humans.…”

Section: Methodsmentioning

confidence: 99%

Influence of Response Variability on the Coding Performance of Central Gustatory Neurons

Lemon

Smith

2006

J. Neurosci.

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We explored how variability in responding to taste stimuli could impact the signaling of taste quality information by neuron types and individual cells in the nucleus of the solitary tract. One hundred sixty-two neurons recorded from anesthetized rats were grouped using multivariate analysis of taste responses to the following (in M): 0.5 sucrose, 0.1 NaCl, 0.01 HCl, and 0.01 quinine-HCl. Neurons fell into one of three groups corresponding to cell types that responded optimally to sucrose, NaCl, or HCl. A statistical model was used to examine whether responses observed among neurons within each group could be correctly attributed to the optimal stimulus or another tastant on the basis of spike count. Results revealed poor classification performance in some cases attributable to wide variations in the sensitivities of neurons that compose a cell type. This outcome leads us to question whether neuron types could faithfully encode a single taste quality. We then theoretically explored whether a hypothetical observer of individual neurons could discriminate between spiking rates to different tastants during the first second of stimulus processing. Spike rate was found to be an unreliable predictor of stimulus quality for each neuron tested. However, additional analyses suggested that taste stimuli could be identified by a reader that attends to the relative spiking activities of different kinds of neurons in parallel. Rather than assigning meaning to individual neurons or categories of them, central gustatory circuits may signal quality information using a strategy that involves the relative activities of neurons with different sensitivities to tastants.

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Functional status of the regenerated chorda tympani nerve as assessed in a salt taste discrimination task

Cited by 43 publications

References 67 publications

Chorda tympani nerve transection at different developmental ages produces differential effects on taste bud volume and papillae morphology in the rat

Chorda tympani nerve transection at different developmental ages produces differential effects on taste bud volume and papillae morphology in the rat

Taste discrimination between NaCl and KCl is disrupted by amiloride in inbred mice with amiloride-insensitive chorda tympani nerves

Influence of Response Variability on the Coding Performance of Central Gustatory Neurons

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