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PubMed1999

Immunocytochemical localization of serotonin and serotonin transporter (SET) in taste buds of rat.

We used an immunocytochemical approach to study the localization of serotonin and its termination system, serotonin transporter (SET), in the taste buds of rats using specific antibodies against serotonin and SET. Under confocal laser scanning microscopy, both serotonin and SET immunoreactivity were detected in the taste buds of rat vallate papillae. Serotonin immunoreactivity was seen in the spindle-shaped cells with apical processes that seemed to be light (Type II) taste cells. SET-immunoreactivity was mainly localized in the periphery or interfaces between the taste cells. Double staining studies revealed that all serotonin-containing taste cells were immunoreactive for SET, while a subclass of SET-positive cells showed serotonin immunoreactivity. These data support the hypothesis that serotonin plays a transmitter role in taste receptor cells and suggest that the serotonin-induced sensation of taste is terminated by serotonin uptake through serotonin transporter.

Animals↗
PubMed1980

Effect of indomethacin on the histological structure and cholinesterase activity of taste buds.

The present work was undertaken to study the effect of indomethacin on the histological structure and cholinesterase activity of taste buds. 16 adult rabbits were divided into four groups; 2 animals of each group were given a daily oral dose of indomethacin and the other 2 animals were used as controls. The animals were sacrificed at 7, 12, 17 and 30 days, respectively. The areas containing circumvallate and foliate papillae were excised for the study of their histological structure and cholinesterase activity. Administration of indomethacin was followed by a decrease in cholinesterase activity and a shrinkage of the reactive zones of the perigemmal, intragemmal and subgemmal plexuses; the cholinesterase activity eventually disappeared on the 17th day. On the 30th day, it reappeared in the above-mentioned sites. The taste buds did not show any degenerative changes and were similar to those of the controls. The significance of these findings is discussed.

Animals↗
PubMed1993

Met-enkephalin-Arg6-Gly7-Leu8-like immunoreactivity in mammalian taste buds.

Light-microscopic immunocytochemistry for various bioactive peptides including some gastroenteropancreatic hormones and a neuronal enzyme, neuron-specific enolase (NSE), was applied to taste buds in the circumvallate papillae of rats, mice and guinea pigs. In all the species positive immunoreactivities were demonstrated for Met-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-8). The Met-Enk-8-like immunoreactivity was confined to parts of the spindle-shaped bud cells. These cells in rats and guinea pigs displayed a concomitant immunoreactivity for NSE. In the mouse taste buds, however, there appeared no such correlation between the immunoreactivities. Considering our previous data, the present finding supports a possibility that opioid peptide(s) derived from preproenkephalin A might be the transmitter(s) of the gustatory cell.

Animals↗
PubMed1983

Taste bud papillae on the retromolar mucosa of the rat, mouse and golden hamster.

The retromolar mucosa of the rat, mouse and golden hamster was observed by light and scanning electron microscopy. Numerous taste bud papillae, each of which formed a low round eminence containing one to several taste buds, were present in the posterior region of the retromolar mucosa, and were especially concentrated in the vicinity of the orifices of the molar glands. This topographical coincidence suggests that the retromolar mucosa of these animals has a functional role as a taste organ. Microridges, arranged in various patterns and small pits, were observed on the surface of the keratinized epithelium of the rat and mouse retromolar mucosa. It appears that the development of numerous microridges is adapted for varied stimuli in the oral cavity.

Animals↗
PubMed1985

Ontogeny of substance P-containing fibers in the taste buds and the surrounding epithelium. I. Light microscopic analysis.

Ontogeny of the substance P-like immunoreactive (SPI) structures in the circumvallate papillae of the rat taste buds was examined by means of indirect immunofluorescence method. SPI fibers in the lamina propria first appeared at gestational day 20, and their quantity increased up to postnatal day 10. On the other hand, SPI fibers in the epithelium were first seen on gestational day 21 and in the taste buds at postnatal day 2-4. These fibers increased remarkably in number after postnatal day 5 and reaching their maximum at postnatal day 20, and thereafter numbers decreasing slightly.

Animals↗
PubMed1977

Histochemical studies on the mucins of the vertebrate tongues. XI. Histochemical analysis of mucosubstances in the lingual glands and taste buds of some birds.

The tongues of six birds were investigated histochemically to determine the distribution and nature of mucosubstances in the lingual glands and taste buds. The anterior lingual glands in sparrow, kingfisher, parrot and pigeon hawk contained only one type of cells (seromucous) elaborating a mixture of neutral mucosubstances, sialomucins and sulfomucins. The anterior lingual glands in fowl and owl contained three distinct types of cells elaborating separately neutral mucosubstances, sialomucins and sulfomucins. The posterior lingual glands in most of the birds investigated except fowl contained only seromucous cells identical to the cells in the anterior lingual glands, while in fowl two distinct cell types were identified: one elaborating sulfomucins and the other sialomucins. Taste buds were found to be restricted in the glandular areas of the tongue in all the birds and always in close association with the gland ducts. Special adenomere cavities were seen only in the tongue of sparrow.

Animals↗
PubMed1983

[Morphometric study of the taste buds in rat tongue after colchicine application to the glossopharyngeal nerve].

Colchicine application on the glossopharyngeal nerve produces a decrease in number and size of the taste buds in the foliate papillae of the tongue, in amount of cells in the buds, as well as certain changes in the nuclear area of these cells on the ipsilateral side. Correlation of normal amount of dark, light and intermediate cells (62, 26, 12, correspondingly) changes: the amount of the dark cells decreases, while the relative amount of the intermediate cells increases. An analogous but less pronounced phenomenon is observed on the contralateral side. Similar changes are also observed after the nerve cutting at the same side where colchicine is applied. But these changes develop more quickly. The results obtained demonstrate that every cell type of the taste bud responds specifically to the trophic effect of the nerves, which is realized with the axonal transport participation.

Animals↗
PubMed1989

Dense-cored vesicles and unusual lamellar bodies in type III gustatory cells in taste buds of rabbit foliate papillae.

Some type III cells in taste buds of rabbit foliate papillae have greatly increased numbers of dense-cored vesicles. Such cells also contain unusual lamellar bodies that resemble those in alveolar type II cells; they consist of alternating dense and light layers with a periodicity of about 4.4 nm. The precise relationship between the vesicles and the lamellar bodies is unknown.

Animals↗
PubMed1984

Fine structure of monoamine-containing basal cells in the taste buds on the barbels of three species of teleosts.

The taste buds on the barbels in three species of teleosts (Cyprinus carpio, Misgurnus anguillicaudatus, Parasilurus asotus) were studied by means of fluorescence- and electron microscopy. Intensely yellow-fluorescent cells, which are disk-shaped and located exclusively in a basal position, are observed in the barbel-buds of all fishes examined. The basal cells contain a large number of small clear vesicles approximately 40-60 nm in diameter, which show a tendency to aggregate in the cytoplasm facing the junction of the nerve terminals; chemically transmitting synapses are seen in the latter region. It is suggested from the present observations that the basal cells in the barbel-bud may originate from Schwann cells and have a dual function both as mechanoreceptors and paracrine elements. Since the administration of 5,6-DHT results in an appearance of small dense vesicles among the small clear vesicles, the possibility exists that the basal cell may be capable of taking up monoamines and storing them in the small clear vesicles.

5,6-Dihydroxytryptamine↗
PubMed1990

Identification of 5'-adenylylimidodiphosphate-hydrolyzing enzyme activity in rabbit taste bud cells using X-ray microanalysis.

X-ray microanalysis has been used to characterize the enzyme activity hydrolyzing the ATP analogue 5'-adenylylimidodiphosphate (AMP-PNP) in taste bud cells. Rabbit foliate papillae fixed with paraformaldehyde and glutaraldehyde were incubated cytochemically with AMP-PNP as the substrate and lead ion as capture agent. The reaction product which appeared on the microvilli of taste bud cells was examined using an energy dispersive X-ray microanalyzer connected to an analytical electron microscope. The X-ray spectrum thus obtained was compared with that obtained from the product obtained from the demonstration of ATPase activity. Comparison of the phosphorus/lead ratios in the two products showed that twice as much phosphorus was released from an AMP-PNP molecule by the activity in question compared with that released from an ATP molecule by ATPase activity. This indicates that the enzyme hydrolyzes AMP-PNP into AMP and imidodiphosphate and that the enzyme is adenylate cyclase or ATP pyrophosphohydrolase, which possesses a similar hydrolytic property, but not ATPase or alkaline phosphatase, which hydrolyzes AMP-PNP into ADP-NH2 and orthophosphate. This paper provides an example of the use of X-ray microanalysis as a tool for enzyme distinction. The method is applicable to a variety of enzymes and tissues.

Adenosine Triphosphate↗
PubMed1985

Structure of taste buds in foliate papillae of the rhesus monkey, Macaca mulatta.

Taste buds in foliate papillae of the rhesus monkey were examined by electron microscopy. Three distinct cell types were identified. Type I cells were narrow elongated cells containing an oval nucleus, bundles of intermediate filaments, several Golgi bodies, and characteristic apical membrane-bounded dense granules. These cells exhibited morphological variations: some had a moderately dense cytoplasm, perinuclear free ribosomes, and flattened sacs of rough endoplasmic reticulum; others had a more lucent cytoplasm, dilated irregular rough endoplasmic reticulum, lysosome-like dense bodies, and lipid droplets. Type II cells typically contained a spherical, pale nucleus, a prominent nucleolus, supranuclear and infranuclear Golgi bodies, mitochondria with tubular cristae, and one or two centrioles. This cell type, too, showed some variation in the relative amounts of ribosomes and smooth endoplasmic reticulum, which varied inversely with each other. Type III cells were characterized by a clear apical cytoplasm essentially devoid of ribosomes and containing microtubules. In a few type III cells, the peri- and infranuclear regions contained many ribosomes and some rough endoplasmic reticulum. In most Type III cells, there were large numbers of dense and clear vesicles in the peri- and infranuclear regions; some of the vesicles were grouped in synapse-like arrangements with adjacent nerves. The morphological variations exhibited by all three cell types could be accounted for by age differences in each of the cells. This would be consistent with the notion that cell renewal occurs in each of the three cell populations.

Animals↗
PubMed1999

Localization of ATP-gated P2X2 and P2X3 receptor immunoreactive nerves in rat taste buds.

P2X receptors have been suggested to play a role in the transduction of sensory signals such as pain and sound. In the present study, polyclonal antibodies against P2X1 to P2X6 receptors were used to localize P2X receptors in circumvallate and fungiform papillae of rats. Nerve fibres innervating the taste buds stained intensely with P2X3 receptor antibodies. P2X3 receptor-positive nerves were observed in the intra- and subgemmal regions. The nerve fibres were also stained with P2X2 receptor antibodies, but the intensity was much lower. The distribution of P2X2 receptor immunoreactivity overlaps with that of P2X3. These results suggest that ATP might be a neurotransmitter in taste reception cells in the taste buds, where it transducts the taste signals to the afferent taste nerves by activating P2X receptors at the synapses. This is the first experiment indicating such a role for ATP, although supplementary functional studies are required.

Adenosine Triphosphate↗
PubMed2001

Molecular cloning and functional characterization of a novel delayed rectifier potassium channel from channel catfish (Ictalurus punctatus): expression in taste buds.

The gustatory system of channel catfish is widely studied for its sensitivity to amino acids. As a first step in identifying the molecular components that play a role in taste transduction in catfish, we cloned the full-length cDNA for Kv2-catfish, a novel K(+) channel that is expressed in taste buds. The deduced amino acid sequence is 816 residues, and shares a 56-59% sequence identity with Kv2.1 and Kv2.2, the other members of the vertebrate Kv2 subfamily of voltage-gated K(+) channels. The Kv2-catfish RNA was expressed in taste buds, brain, skeletal muscle, kidney, intestine and gills, and its gene is represented as a single copy in the catfish genome. Recombinant channels expressed in Xenopus oocytes were selective for K(+), and were inhibited by tetraethylammonium applied to the extracellular side of the membrane during two-electrode voltage clamp analysis with a 50% inhibitory constant of 6.1 mM. The channels showed voltage-dependent activation, and did not inactivate within 200 ms. Functionally, Kv2-catfish is a voltage-gated, delayed rectifier K(+) channel, and its primary structure is the most divergent sequence identified among the vertebrate members of the Kv2 subfamily of K(+) channels, being related equally well to Kv2.1 and Kv2.2.

Amino Acid Sequence↗
PubMed1979

Taste buds in vallate papillae grafted to the anterior chamber of the eye.

Vallate papillae from rats were grafted to the anterior chamber of the eye of the same animal. Longterm grafts showed small taste buds located in epitelial cavities which were probably the remnants of trench walls. These grafts have been reinnervated by local nerves. Excretory ducts and serous acini of Von Ebner's glands were also present. The latter showed secretory granules in their cells. The specificity of the nerve fibers and of the epithelium in relation to the induction of taste bud differentiation are discussed.

Animals↗
PubMed1984

Carbonic anhydrase is associated with taste buds in rat tongue.

A modification of Hansson's histochemical technique was used to reveal carbonic anhydrase activity in mounted cryostat sections of the circumvallate papillae from rat tongue. An intensely positive reaction was found at the level of the neck of the papilla, associated with the taste buds. Lingual glands also contained abundant carbonic anhydrase activity. The presence of carbonic anhydrase in taste buds, as well as our previous observation that it is found in a population of olfactory receptor cells, may indicate a role for the enzyme in gustative and olfactory phenomena.

Animals↗
PubMed2005

Expression, physiological action, and coexpression patterns of neuropeptide Y in rat taste-bud cells.

Recent studies have suggested that neuropeptides could play previously unrecognized functional roles in peripheral gustation. To date, two peptides, cholecystokinin and vasoactive intestinal peptide, have been localized to subsets of taste-bud (TB) cells (TBC) and one, cholecystokinin, has been demonstrated to produce excitatory physiological actions. This study extends our knowledge of neuropeptides in TBC in three significant ways. First, using techniques of immunocytochemistry and RT-PCR, evidence is presented for the expression of a third peptide, neuropeptide Y (NPY). Like other peptide expression patterns, NPY expression is circumscribed to a subset of cells within the taste bud. Second, using physiological studies, we demonstrate that NPY specifically enhances an inwardly rectifying potassium current via NPY-Y1 receptors. This action is antagonistic to the previously demonstrated inhibitory effect exerted by cholecystokinin on the same current, thus providing important clues to their signaling roles in the TB. Third, using the technique of double-labeled fluorescent immunocytochemistry, the relationship of three subsets of neuropeptide-expressing TB cells to one another was examined. Remarkably, NPY expressions, although fewer in number than either the cholecystokinin or vasoactive intestinal peptide subsets, overlapped 100% with either peptide. Collectively, these three observations transform previously suggestive roles of neuromodulation by peptides in TB cells to more concrete signaling pathways. The extensive colocalization of these peptides suggests they may be subject to similar presynaptic influences of release yet have antagonistic postsynaptic actions. The convergence or divergence of these postsynaptic actions awaits further investigation.

Animals↗
PubMed1996

GUST27 and closely related G-protein-coupled receptors are localized in taste buds together with Gi-protein alpha-subunit.

Gustatory, like olfactory signalling is probably mediated by seven-transmembrane receptors and coupling GTP-binding proteins (G proteins). We investigated the expression of a subset of these receptors and the Gi protein alpha-subunit by using their specific antibodies. Based on our previous finding that the mRNA for GUST27, one of these receptors, is expressed in rat lingual epithelia, we first prepared an antibody to the synthetic nonapeptide, H-Ser-Tyr-Ser-Gln-Ile-Ala-Ser-Ser-Leu-OH, which corresponds to the third intracellular domain of GUST27 and also to those of a subset of related receptors whose occurrence can be predicted by PCR. Immunohistochemical studies with rat circumvallate papillae indicated that the anti-GUST27 antibody reacted with many of the taste buds examined, with strong signals appearing in particular taste cells. We then carried out a similar immunohistochemical experiment with an antibody to the Gi protein alpha-subunit and found that this subunit is also expressed in taste buds as demonstrated in the case of gustducin and transducin. Taken together, these results strongly suggest that GUST27 and closely related receptors, as well as Gi alpha proteins, are involved in intracellular taste signal transduction.

Amino Acid Sequence↗