Transmission-electron microscopy of cat taste buds confirmed that, as in other mammals, each taste bud comprised four distinct types of cells: Type I, Type II, Type III (gustatory), and Type IV (basal) cells. Gustatory cells made synaptic contacts with nerves to which synaptic vesicles were gathered, The following are the main findings on the cat gustatory cells:
1) The synaptic vesicles of gustatory cells were essentially all dense-cored in type; small clear vesicles, which usually are intermingled in other mammals, could not be found,
2) The vesicles were accumulated not only in the synaptic area but also in the basal cytoplasm, This implies endocrine and paracrine functions,
3) On the basis of the fine structure of the vesicles, two subtypes of gustatory cells were discriminated. A large part of the cells contained vesicles measuring about 180 nm in diameter, while a small part had smaller ones of about 100 nm in diameter. This is the first demonstration of a dual population of gustatory cells in mammals, suggesting different messenger substances utilized.