• International Journal of Oral Biology
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• v.41 no.1
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• pp.25-32
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• 2016

The tongue has 4 kinds of papillae, which are filiform, fungiform (FU), foliate (FO) and circumvallate papilla (CV). Tongue papillae except filiform papilla include taste buds. The papillae differ in taste sensitivities, likely due to differential expression of taste receptors. In this study, we evaluated differences in the expression levels of taste receptors in FU, FO and CV. Male DBA2 mice, 42-60 days old, were used in the study. Messenger RNAs were extracted from the murine epithelial tissues including FU, FO and CV. Cloned DNAs were synthesized by reverse transcription. Quantitative PCRs (qPCRs) were performed to determine mRNA expression levels of taste receptors. Results of qPCR revealed that the relative expression levels and patterns were different among FU, FO and CV. All three type 1 taste receptors were expressed FU, FO and CV at varying relative expression levels. All 35 kinds of type 2 taste receptors showed higher expression in FO and CV than in FU. Tas2r108 and Tas2r137 showed the two highest expression levels in all tested papillae. The differential expression levels and patterns of taste receptors among the three papillae could contribute to the different physiological sensitivities by tongue areas. Additional studies such as in situ hybridization or taste receptor cell activity recording is necessary to elucidate the functional relationship between expression levels of taste receptors and taste sensitivity.

• International Journal of Oral Biology
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• v.31 no.3
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• pp.99-105
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• 2006

Von Ebner's glands (vEG) are minor salivary glands associated with circumvallate and foliate papilla. The secretions of vEG consist of microenvironment of the taste buds in the circumvallate and foliate papillae, and thus saliva from vEG plays a role in the perception of taste. The $Ca^{2+}$ signaling system in rat vEG acinar cell was examined using the $Ca^{2+}$-sensitive fluorescent indicator Fura-2. Agonist-induced increase in intracellular $Ca^{2+}\;([Ca^{2+}]_i)$ was stimulated by carbachol (CCh) and substance P (SP), but not by norepinephrine (NE), and recovered to control levels by their receptor antagonists dose-dependently. The effects were also observed in $Ca^{2+}$-free medium, suggesting mobilization from intracellular $Ca^{2+}$ store. These results in the vEG acinar cell indicate that 1) $[Ca^{2+}]_i$ is at least regulated by muscarinic and neurokininergic (NK1) receptors; 2) the increases in $[Ca^{2+}])i$ activated by CCh and SP are mainly mediated by discharge of cytosolic calcium pool.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.6
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• pp.455-460
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• 2009

Glutamate-induced cobalt uptake reveals that non-NMDA glutamate receptors (GluRs) are present in rat taste bud cells. Previous studies involving glutamate induced cobalt staining suggest this uptake mainly occurs via kainate type GluRs. It is not known which of the 4 types of taste bud cells express subunits of kainate GluR. Circumvallate and foliate papillae of Sprague-Dawley rats (45~60 days old) were used to search for the mRNAs of subunits of non-NMDA GluRs using RT-PCR with specific primers for GluR1-7, KA1 and KA2. We also performed RT-PCR for GluR5, KA1, $PLC\beta2$, and NCAM/SNAP 25 in isolated single cells from taste buds. Taste epithelium, including circumvallate or foliate papilla, express mRNAs of GluR5 and KA1. However, non-taste tongue epithelium expresses no subunits of non-NMDA GluRs. Isolated single cell RT-PCR reveals that the mRNAs of GluR5 and KA1 are preferentially expressed in Type II and Type III cells over Type I cells.

• International Journal of Oral Biology
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• v.33 no.3
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• pp.83-89
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• 2008

Glutamate-induced cobalt uptake reveals non-NMDA glutamate receptors (GluRs) in rat taste bud cells. Previous studies suggest that glutamate-induced cobalt uptake in taste cells occurs mainly via kainate type GluRs. Cobaltstained cells were immunoreactive against GluR6 and KA1 subunits of GluRs. However, the functions of those type of receptors are not known yet. It is important question which types of taste cells are cobalt-stained when stimulated by glutamate and whether they express these kinds of GluRs. Circumvallate and foliate papilla of Sprague-Dawley rats (45-60 days old) were used. A cobalt-staining technique combined with immunohistochemistry against specific markers for taste bud cell types, such as blood group H antigen (BGH), $\alpha$-gustducin (Gus), or neural cell adhesion molecule (NCAM) was employed. We also performed double labeling of GluR6 or KA1 subunits of GluR with each specific marker for taste bud cell types. Lots of cobaltstained taste bud cells expressed Gus-like immunoreactivity, and subsets of the cobalt stained cells appeared NCAM- or BGH-like immunoreactivity. Stimulation with 1 mM glutamate significantly increased the number of cobaltstained cells in Gus-like immunoreactive cells, but not in NCAM- or BGH-like immunoreactive cells. In the double labeling experiments, GluR6 and KA1 subunits of GluRs were mainly expressed with Gus. These results suggest that kainate glutamate receptors preferentially expressed in type II taste bud cells in rat.