Neural activity of chorda tympani mechanosensitive fibers during licking behavior in rats

Ryuji Matsuo, Tomio Inoue, Yuji Masuda, Osamu Nakamura, Yoji Yamauchi, Toshifumi Morimoto

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

The chorda tympani nerve, supplying the anterior two-thirds of the tongue, contains gustatory and mechanosensitive afferent fibers. We have analyzed discharge patterns in rats of various fibers recorded from dissected nerve filaments during licking behavior of which 4 were taste-sensitive and 12 mechanosensitive. The incidence of these two types was estimated electrophysiologically under anesthesia and their conduction velocity measured. Recordings in freely moving animals showed that the mechanosensitive fibers innervating the dorsal part of the tongue gave two burst discharges per lick, suggesting that contact of the tongue with the upper incisors and/or lip occurred during tongue protrusion and retraction. The fibers from the tip of the tongue showed one burst discharge per lick, which was the response to contact with a drinking spout. No rhythmical discharges synchronized with lick signals were observed in the fibers from the lateral part of the tongue or the taste-sensitive fibers. Such mechanoreceptor discharges were difficult to detect in recordings from the whole chorda tympani nerve. This masking of responses was due mainly to activation of a small number of mechanosensitive fibers by licking-induced mechanical stimulation. The lubricating action of saliva also decreased mechanoreceptor sensitivity. Despite their small number, the mechanosensitive fibers had axons with faster conduction velocities (larger diameter) than the taste-sensitive fibers. This was probably the reason why dissected nerve bundles more frequently showed mechanical than taste responses in conscious rats.

Original languageEnglish
Pages (from-to)289-298
Number of pages10
JournalBrain Research
Volume689
Issue number2
DOIs
Publication statusPublished - Aug 21 1995

Keywords

  • Chorda tympani
  • Conduction velocity
  • Licking
  • Mechanical stimulation
  • Rat
  • Saliva
  • Taste

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology

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    Matsuo, R., Inoue, T., Masuda, Y., Nakamura, O., Yamauchi, Y., & Morimoto, T. (1995). Neural activity of chorda tympani mechanosensitive fibers during licking behavior in rats. Brain Research, 689(2), 289-298. https://doi.org/10.1016/0006-8993(95)00582-B