Effects of Chorda Tympani Nerve Anesthesia on Taste Responses in the NST

Dinkins, Mark E.; Travers, Susan P.

doi:10.1093/chemse/23.6.661

Cited by 13 publications

(20 citation statements)

References 34 publications

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“…Although contralateral changes have been noted in other sensory systems following ipsilateral perturbations, ipsilateral changes are far more pronounced (e.g., Takemura et al 1998). Importantly, in the present study, the topographic organization, as well as the mean spontaneous rate on the contralateral side were not different from those observed in another recent study in our lab that used a similar design (t ϭ 0.24, df ϭ 56.6, P ϭ 0.81) (Dinkins and Travers 1998).…”

Section: Chorda Tympani Transectioncontrasting

confidence: 60%

Altered Taste Responses in Adult NST After Neonatal Chorda Tympani Denervation

Dinkins

Travers

1999

Journal of Neurophysiology

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Anatomic and behavioral changes have been observed in the taste system after peripheral deafferentation, but their physiological consequences remain unknown. Interestingly, a recent behavioral study suggested that peripheral denervation could induce central plasticity. After neonatal chorda tympani (CT) transection, adult rats demonstrated a marked preference for a normally avoided salt, NH(4)Cl. In the present study, taste responses were recorded from the nucleus of the solitary tract (NST) in similarly CT-denervated rats to investigate a physiological basis for this behavioral phenomenon. We hypothesized that alterations in functional connectivity of remaining afferent nerves might underlie the behavioral change. Specifically, if NST neurons formerly activated by sodium-selective CT fibers were instead driven by more broadly tuned glossopharyngeal (GL) afferents, neural coding of salt responses would be altered. Such a change should be accompanied by a shift in orotopic representation and increased NH(4)Cl responses. This hypothesis was not supported. After CT denervation, orotopy was unaltered, NH(4)Cl responsiveness declined, and no other changes occurred that could simply explain the behavioral effects. Indeed, the most pronounced consequence of CT denervation was a 68% reduction in NaCl responses, supporting previous evidence for a critical role of this nerve in coding sodium salts. In addition, we found "reorganizational" changes similar to, albeit smaller than, those observed in other sensory systems after deafferentation. There was a trend for increased responses elicited by stimulation of receptor subpopulations innervated by the GL and greater superficial petrosal nerves. In addition, the spontaneous rate of nasoincisor duct-responsive cells increased significantly. This effect on spontaneous rate is opposite to that produced by CT anesthesia, suggesting that acute versus chronic denervation may affect central taste neurons differently. In conclusion, the taste system at the medullary level seems more resistant to large-scale plasticity than other sensory systems, but nevertheless reacts to lost afferent input. Because the most robust plastic changes have been documented at cortical levels in other sensory pathways, the substrate for the behavioral effect of neonatal CT transection may be located more centrally in the gustatory system.

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Section: Chorda Tympani Transectioncontrasting

confidence: 60%

Altered Taste Responses in Adult NST After Neonatal Chorda Tympani Denervation

Dinkins

Travers

1999

Journal of Neurophysiology

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“…In the clinical studies, the taste of QHCl was intensified and the taste of NaCl was diminished at areas innervated by the glossopharyngeal nerve on both sides of the tongue if CT nerves are anesthetized bilaterally (52). However, a recent study reported that average anterior tongue responses were eliminated, but no compensatory increases in palatal or posterior tongue responses were observed following anesthetization of the CT, indicating that other mechanisms may be involved to compensate for the loss of taste input (10).…”

Section: Discussionmentioning

confidence: 99%

Taste-responsive neurons in the nucleus of the solitary tract receive gustatory information from both sides of the tongue in the hamster

Li¹,

Mao²,

Cho³

2008

American Journal of Physiology-Regulatory, Integrative and Comp

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Taste receptors on the left and right sides of the anterior tongue are innervated by chorda tympani (CT) fibers, which carry taste information to the ipsilateral nucleus of the solitary tract (NST). Although the anterior tongue is essential for taste, patients with unilateral CT nerve damage often report no subjective change in their taste experience. The standing theory that explains the taste constancy is the "release of inhibition", which hypothesizes that within the NST there are inhibitory interactions between inputs from the CT and glossopharyngeal nerves and that the loss of taste information from the CT is compensated by a release of inhibition on the glossopharyngeal nerve input. However, the possibility of compensation by taste input from the other side of the tongue has never been investigated in rodents. We recorded from 95 taste-responsive neurons in the NST and examined their responsiveness to stimulation of the contralateral CT. Forty-six cells were activated, mostly with excitatory responses (42 cells). Activation of NST cells induced by contralateral CT stimulation was blocked by microinjection of lidocaine into the contralateral NST but was not affected by anesthetization of the contralateral parabrachial nuclei (PbN). In addition, the NST cells that were activated by contralateral CT stimulation showed reduced responsiveness to taste stimulation after microinjection of lidocaine into the contralateral NST. These results demonstrate that nearly half of the taste neurons in the NST receive gustatory information from both sides of the tongue. This "cross talk" between bilateral NST may also contribute to the "taste constancy".

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“…This procedure was reported to result in anesthesia of the CT in < 1 min (Dinkins & Travers, 1998). Then, physiological saline was injected through the tubing, which has been reported to lead to recovery of CT responses in < 10 min (Dinkins & Travers, 1998). At the end of the experiment, an equal volume of Evans blue was applied in the same manner, and confirmed to flood the tympanic bulla to access the CT.…”

Section: Surgery and Ct Anesthesia/transectionmentioning

confidence: 99%

Gustatory modulation of the responses of trigeminal subnucleus caudalis neurons to noxious stimulation of the tongue in rats

Boucher

Felizardo

Klein

et al. 2013

Eur J of Neuroscience

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Certain tastants inhibit oral irritation by capsaicin, whereas anesthesia of the chorda tympani (CT) enhances oral capsaicin burn. We tested the hypothesis that tastants activate the CT to suppress responses of trigeminal subnucleus caudalis (Vc) neurons to noxious oral stimuli. In anesthetized rats, we recorded Vc unit responses to noxious electrical, chemical (pentanoic acid, 200 μm) and thermal (55 °C) stimulation of the tongue. Electrically evoked responses were significantly reduced by a tastant mix and individually applied NaCl, monosodium glutamate (MSG), and monopotassium glutamate. Sucrose, citric acid, quinine and water (control) had no effect. Pentanoic acid-evoked responses were similarly attenuated by NaCl and MSG, but not by other tastants. Responses to noxious heat were not affected by any tastant. Transection and/or anesthesia of the CT bilaterally affected neither Vc neuronal responses to electrical or pentanoic acid stimulation, nor the depressant effect of NaCl and MSG on electrically evoked responses. Calcium imaging showed that neither NaCl nor MSG directly excited any trigeminal ganglion cells or affected their responses to pentanoic acid. GABA also had no effect, arguing against peripheral effects of GABA, NaCl or MSG on lingual nocicepive nerve endings. The data also rule out a central mechanism, as the effects of NaCl and MSG were intact following CT transection. We speculate that the effect is mediated peripherally by the release from taste receptor cells (type III) of some mediator(s) other than GABA to indirectly inhibit trigeminal nociceptors. The results also indicate that the CT does not exert a tonic inhibitory effect on nociceptive Vc neurons.

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Effects of Chorda Tympani Nerve Anesthesia on Taste Responses in the NST

Cited by 13 publications

References 34 publications

Altered Taste Responses in Adult NST After Neonatal Chorda Tympani Denervation

Altered Taste Responses in Adult NST After Neonatal Chorda Tympani Denervation

Taste-responsive neurons in the nucleus of the solitary tract receive gustatory information from both sides of the tongue in the hamster

Gustatory modulation of the responses of trigeminal subnucleus caudalis neurons to noxious stimulation of the tongue in rats

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