Fos positive neurons in the brain stem and amygdala mostly express vesicular glutamate transporter 3 after bitter taste stimulation

The present study examined the relationship between vesicular glutamate transpoter-3 (VGLUT3) positive cells and the activation of neurons in the brainstem and amygdala by bitter taste, using double-labeling immunohistochemistry. Conscious animals were subjected to intraoral bitter taste stimulation with quinine solution. Following this, neuronal activation was assessed by c-Fos expression and an analysis of c-Fos expression cells, VGLUT3 positive cells and double-labeled cells was made in the nucleus of the solitary tract (NST), the parabrachial nucleus (PBN) and amygdala. Results showed that intraoral bitter taste stimulation led to significant increases in the number of c-Fos-expressing and double-labeled cells in the NST, PBN and amygdala. Results also showed a decrease in the number of c-Fos-positive and double-labeled cells in the amygdala, in comparison with neurons in the brainstem, after bitter taste stimulation. These results suggest that bitter taste activates cells in the NST, PBN and amygdala and these effects are partly mediated by VGLUT3 positive cells. Moreover, double-labeled neurons also exhibited a preferential distribution after quinine stimulation compared to water stimulation.

► Neurons in the NST, PBN and amygdala are activated after intraoral bitter taste stimulation.
► Bitter taste perception in the NST, PBN and amygdala may be partly mediated by VGLUT3 positive cells.
► Double-labeled cells exhibited a preferential distribution after quinine stimulation compared to controls in the brain stem.