Effects of p-chlorophenylalanine on rabbit taste receptor cells.

Abstract

Summary. By administration of p-chlorophenylalanine (PCPA), a synthetic inhibitor of 5-hydroxytryptamine (5-HT), to rabbits, granular vesicles in the taste receptor cells remarkably decreased their contents.The recovery of this core substance depletion occurred in specimens killed on the 15th day after injection of the drug and in animals injected with 5-hydroxytryptophan (5-HTP) after treatment with PCPA.Electron microscope observation suggests that granular vesicles in the receptor cells are 5-HT-storing particles and favors the view based on recent fluorescence histochemistry which indicates the presence of a biogenic monoamine, presumably 5-HT, in rabbit foliate taste bud cells.A considerable variation in the appearance of mammalian taste bud cells has been demonstrated by light-and electron microscopy. On this basis, we have classified rabbit taste bud cells into three types and designated them as type I (dark cells), type II (light cells), and type III (distinctly receptor cells) by distinct cytoplasmic features and the manner of cell to nerve contact (MURRAY et al., 1969;FUJIMoTo and MURRAY, 1970;MURRAY, 1973).The type III cells resemble many of the type II cells in general shape and electron density of the cytoplasm but fundamentally differ from all the type II cells in their afferent synaptic specializations to the intragemmal nerve fibers; these include increased density of the plasma membrane along the nerves and aggregations of vesicles against the density.These vesicles are of two types, one, an electron lucent type of synaptic vesicle, and the other, less frequent, but always containing densely staining core. The latter, designated as granular vesicles in this article, is uniformly spherical in form ranging from 60 to 160 mp in diameter and mostly found in the deeper part of the cytoplasm below the nucleus and around the synaptic regions, while dense secretory granules of the type I cells apparently derived from the Golgi complex always exist above the nucleus. The core substance of these granular vesicles is usually vaguely granular rather than homogeneous like the dense granules of the type I cells and separated from the limiting membrane by a very narrow electron lucent "peripheral halo."The occurrence of granular vesicles in the cytoplasm of the type III cells is one of the distinctive features which discriminate this cell type from the other ones. They 365

Pre‐ and postnatal development of rabbit foliate papillae with special reference to foliate gutter formation and taste bud and serous gland differentiation

“…Such dark cored vesicles accumulate in the basal part of the cytoplasm, especially near the cell t o nerve contact region, after they are segregated from Golgi apparatus. We previously reported that dark cored vesicles contain serotonin and may participate in a serotonergic modulation of a cholinergic synaptic transmission based on their ultrastructural changes after administration of p-chlorophenylalanine, a synthetic inhibitor of serotonin (Fujimoto, 1982), and immunocytochemistry using anti-histamine sera (Fujimoto et al, 1987). However, we do not rule out the possibility of their paracrine action, as indicated by Toyoshima et al (1984).…”

Immunocytochemistry on the Localization of 5-Hydroxytryptamine in Monkey and Rabbit Taste Buds

“…Recently Takeda and Kitao [1980] reported that gustatory cells of mouse circumvallate taste buds have an ability of taking up and storing monoamines. Fujimoto [1982] observed the remarkable depletion of the core substance after administration of />-cholorophenylalanine, a synthetic inhibitor of 5-HT. to rabbits and the recovery of the core substance by injection of 5-hydroxytryptophan.…”