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The expression of molecules involved in the transductory cascade of the sense of taste (TRs, α-gustducin, PLCβ2, IP3R3) has been described in lingual taste buds or in solitary chemoreceptor cells located in different organs. At the laryngeal inlet, immunocytochemical staining at the light and electron microscope levels revealed that α-gustducin and PLCβ2 are mainly localized in chemosensory clusters (CCs), which are multicellular organizations differing from taste buds, being generally composed of two or three chemoreceptor cells. Compared with lingual taste buds, CCs are lower in height and smaller in diameter. In laryngeal CCs, immunocytochemistry using the two antibodies identified a similar cell type which appears rather unlike the α-gustducin-immunoreactive (IR) and PLCβ2-IR cells visible in lingual taste buds. The laryngeal IR cells are shorter than the lingual ones, with poorly developed basal processes and their apical process is shorter and thicker. Some cells show a flask-like shape due to the presence of a large body and the absence of basal processes. CCs lack pores and their delimitation from the surrounding epithelium is poorly evident. The demonstration of the existence of CCs strengthens the hypothesis of a phylogenetic link between gustatory and solitary chemosensory cells. [ABSTRACT FROM AUTHOR]

The presence of solitary chemosensory cells was studied in rat vallate papillae during the first week of post-natal life by α-gustducin immunocytochemistry. In 1- to 3-day-old rats, isolated α-gustducin-immunoreactive cells were found within the epithelium of the vallate papilla. These cells, mainly located in the basal layer, were scattered among keratocytes and wrapped in α-gustducin-negative epithelial cells in a glia-like fashion. The α-gustducin-immunoreactive cells were usually round and some of them gave rise to short, large processes directed towards the lumen of the oral cavity or the basal lamina. Rarely, some cells showed an evident bipolar shape. Small taste buds containing either α-gustducin-immunoreactive or α-gustducinnegative cells appeared in the vallate papillae of 4-day-old rats in which isolated, bipolar-shaped α-gustducin-immunoreactive cells were also found. After the first week of post-natal life, the taste buds appeared basically similar to those of adult animals. In conclusion, the present study demonstrates that the presence of epithelial cells with characteristics of solitary chemosensory cells precedes the development of the taste buds. [ABSTRACT FROM AUTHOR]