Effect of monoamines on the taste buds in the mouse

Abstract

Mouse taste buds were investigated following administration of monoamines and their precursors by fluorescence and electron microscopy. The appearance of fluorescent cells within the taste bud and the ultrastructural changes of vesicles in the gustatory cells were due to the treatment of 5-hydroxytryptophan. Small dense-cored vesicles (30-60 nm in diameter) appeared throughout the cytoplasm and accumulated especially at the presynaptic membranes of afferent synapses. Large dense-cored vesicles (80-100 nm) increased twice in number, and electron densities of their cores became more dense as compared with untreated mice. Fluorescent cells appeared in the taste bud of L-DOPA treated mice, whereas no ultrastructural changes were observed. These results suggest that the gustatory cells of the taste bud are capable of taking up and storing monoamines, which might act as neurotransmitters from the gustatory cells to the nerves.

Monoamines of taste buds in the fungiform and foliate papillae of the mouse.

“…X 10,000 DISCUSSION Following treatment with the amine precursors we observed the appearance of fluorescent cells in the taste buds of the foliate papillae and also the ultrastructural changes of vesicles in the gustatory cells. The results showed that gustatory cells in the foliate papillae of the mouse were capable of taking up amine precursors as previously observed in the circumvallate papillae (TAKEDA, 1977;TAKEDA and KITAO, 1980). NADA andHIRATA (1975, 1976) have also observed fluorescent cells in the taste buds of the foliate and vallate papillae in the rabbit.…”

The microphysiology of peripheral taste organs

“…However, closer analysis of the histofluorescence emission spectrum led Nada and Hirata (1975) to conclude that the monoamine serotonin, rather than a catecholamine, was present in taste cells. Immunocytochemical and electron microscopic studies have vindicated this latter report (Takeda and Kitao, 1980;Welton et al, unpublished observations;see Roper, 1992, for other references) (Fig. 5).…”

Separate Populations of Receptor Cells and Presynaptic Cells in Mouse Taste Buds

“…Second, we observed that SNAP25 cells very often express AADC and GAD1, enzymes essential in the biosynthesis of biogenic amine and GABA neurotransmitters, respectively. A considerable body of literature substantiates that small numbers of cells within taste buds selectively take up and accumulate the serotonin precursor 5-hydroxytryptophan and synthesize serotonin under physiological conditions (Takeda and Kitao, 1980;Nagai et al, 1998). Recent physiological studies using biosensors have demonstrated serotonin release from taste buds after stimulation with tastants (Huang et al, 2005).…”

“…Although the precise role of these neurotransmitters in taste signaling remains to be established, serotonin for one has been localized to synapses in taste buds (Takeda and Kitao, 1980). AADC (also called DOPA decarboxylase), is a biosynthetic enzyme common to the pathways for serotonin, dopamine, norepinephrine, and epinephrine.…”