[Development of the taste buds in rat embryogenesis]

Electron microscopic studies have been made on the developing taste buds in fungiform and vallate papillae of prenatal rats. Three stages of differentiation of these buds are described. The first stage is characterized by presence of the nervous fibers in the connective tissue of the papillae and dense granules of various size, as well as dense-cored vesicles (500-700 A in diameter) in the basal parts of some epithelial cells at the top of the papillae (16-17th days of gestation). The second stage is characterized by nerve processes entering the epithelium and by formation of afferent synaptic contacts between the differentiating epithelial cells and the nervous fibers (19th day of gestation). At the third stage, the cluster of differentiating epithelial cells attains a form which is similar to mature taste buds (21-22nd days of gestation). Thus, to the birthday of rats, differentiation of the basal parts of the taste buds takes place, whereas the apical parts of the taste buds remain undeveloped and do not communicate with the oral cavity. Peculiarities of fine structure of differentiating epithelial cells at the three stages are discussed.