J Vet Sci.  2014 Dec;15(4):459-464. 10.4142/jvs.2014.15.4.459.

Intragastric gavage with denatonium benzoate acutely induces neuronal activation in the solitary tract nucleus via the vagal afferent pathway

Affiliations
  • 1Department of Anatomy and Cell Biology, College of Veterinary Medicine, and Research Institute for Veterinary Science, Seoul National University, Seoul 151-742, Korea. vetmed2@snu.ac.kr
  • 2Department of Anatomy, College of Veterinary Medicine, Kangwon National University, Chuncheon 200-701, Korea.
  • 3Division of Metabolism and Functionality Research, Korea Food Research Institute, Sungnam 463-746, Korea.

Abstract

Natural toxic substances have a bitter taste and their ingestion sends signals to the brain leading to aversive oral sensations. In the present study, we investigated chronological changes in c-Fos immunoreactivity in the nucleus tractus solitarius (NTS) to study the bitter taste reaction time of neurons in the NTS. Equal volumes (0.5 mL) of denatonium benzoate (DB), a bitter tastant, or its vehicle (distilled water) were administered to rats intragastrically. The rats were sacrificed at 0, 0.5, 1, 2, 4, 8, or 16 h after treatment. In the vehicle-treated group, the number of c-Fos-positive nuclei started to increase 0.5 h after treatment and peaked 2 h after gavage. In contrast, the number of c-Fos-positive nuclei in the DB-treated group significantly increased 1 h after gavage. Thereafter, the number of c-Fos immunoreactive nuclei decreased over time. The number of c-Fos immunoreactive nuclei in the NTS was also increased in a dose-dependent manner 1 h after gavage. Subdiaphragmatic vagotomy significantly decreased DB-induced neuronal activation in the NTS. These results suggest that intragastric DB increases neuronal c-Fos expression in the NTS 1 h after gavage and this effect is mediated by vagal afferent fibers.

Keyword

bitter tastant; c-Fos; nucleus tractus solitarius; vagal afferent fibers; vagotomy
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