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PubMed1993

[The neurophysiological changes in the taste reactions of the frog glossopharyngeal nerve evoked by the chronic administration of ethanol].

The latency of impulse responses of taste receptors to different taste stimuli was studied and frequency-temporal characteristics of the responses were analysed during chronic ethanol injection. It was shown that the latency of taste responses depending un the type of taste stimuli was increased 2-4.5 times after 7-14 days of ethanol injection. The latency of responses tended to shortening within 30 days of ethanol injection. The continued ethanol injection brought about a renewal of increase in the response latency. The changes in the dynamics of the impulse taste responses to salt and sour stimuli were found within 90 days of ethanol injection. The findings indicate that both the transduction of taste stimuli and the conduction of sensitive nerve fibres are disturbed.

Animals↗
PubMed1996

[Drug-induced taste disorders].

Taste disorders may have diverse uncomfortable consequences such as reduced quality of life, weight loss and possibly professional disability. The sense of taste depends on many factors. Thus various conditions may cause taste disorders, drugs being one of them. The list of drugs being able to cause taste disorders as adverse drug reaction is long and there are many such cases reported to the Swiss Drug Monitoring Center (SANZ). The possibility of an unwanted side effect should be taken into account if a patient complains about taste disorders, such as reduced or changed sense of taste.

Adult↗
PubMed1996

Differential expression of brain-derived neurotrophic factor and neurotrophin 3 mRNA in lingual papillae and taste buds indicates roles in gustatory and somatosensory innervation.

Although many studies have demonstrated the dependency of taste bud function and/or survival on intact innervation, relatively few have dealt with the development of taste bud innervation. Using in situ hybridization histochemistry, we show that brain-derived neurotrophic factor (BDNF) and neurotrophin 3 (NT3) mRNA are expressed in a specific pattern in the taste buds, tongue papillae, and lingual epithelium during development and that expression persists into adulthood. BDNF mRNA is expressed in a fraction of the taste cells of the developing and adult taste buds in rats, showing different labeling intensities among the labeled cells. NT3 and mRNA seems to be located in areas other than those where BDNF mRNA is expressed, mainly in the superior epithelial surfaces of circumvallate papillae, the outer surface epithelium of foliate papilae, the superior surface and the lateral epithelium of the fungiform papillae, and the epithelium of the filiform papillae. NT3 mRNA labeling is also observed among muscle and connective tissue of the tongue. The morphological appearance, expression of NT3 mRNA, and ramification of nerve fibers in defined epithelial structures in the posterior wall of the anterior filiform papillae suggest the existence of a mechanosensory apparatus in these papillae. Nerve growth factor and neurotrophin 4 probes did not give rise to selective labeling in tongue, although their presence cannot be totally excluded. Based on present and prior studies, we suggest that BDNF is needed during initiation and for maintenance of gustatory innervation of taste buds and gustatory papillae and that NT3 is mainly needed for somatosensory innervation of the tongue.

Animals↗
PubMed1977

Intraperitoneal transplants of taste buds in the newt.

Autografts of tongue onto the liver contained taste buds without nerves for up to 30 days. However, these denervated taste buds were generally smaller than normal and distorted in structure. Nerve fibers invaded the graft from the liver and after 30 days normal appearing taste buds were found only in implants of tongue which contained extensive nerve fibers. Thus it appears that certain visceral nerves can maintain and possibly induce taste bud formation in implants of tongue. This is interpreted as additional evidence for the trophic influence of nerves upon taste buds. Moreover, this ability to maintain taste buds is not restricted to gustatory nerves in the newt.

Animals↗
PubMed1982

Comparative study of ultrastructures of the lateral-line organs and the palatal taste organs in the African clawed toad, Xenopus laevis.

The fine structure of the lateral-line organ and the palatal taste organ in the African clawed toad, Xenopus laevis, was examined by means of electron microscopy. The lateral-line organ consisted of hair and accessory cells. The apical surface of a hair cell was studded with one kinocilium and 20 to 40 stereocilia. Synaptic bodies and subsynaptic cisternae were found in the cytoplasm of a hair cell adjacent to the synaptic contacts with the afferent and the efferent nerve endings, respectively. Crystalline bodies were observed in both the nucleoplasm and the cytoplasm of almost all hair cells. The palatal taste organ consisted of three types of cells: the taste, sustentacular, and the Merkel cells. The taste cells contained numerous dense-cored vesicles which accumulated in close association with both the afferent synapses and the basal plasma membrane. The possibility was raised from the ultrastructural results that these vesicles had dual functions as both neurotransmitter and hormone. The existence of Merkel cells in the palatal taste organ suggested that this organ might function not only as a chemoreceptor but also as a mechanoreceptor. In spite of possible chemosensory function of the lateral-line organ in Xenopus, its ultrastructure was significantly different from that of the typical gustatory organ, the palatal taste organ, in this animal.

Animals↗
PubMed1987

Taste bud development in chickens (Gallus gallus domesticus).

Oral epithelium in the anterior mandibular glands region was examined in embryonic, hatchling, and mature chickens to establish the timing of morphologic events during taste bud ontogeny. Hematoxylin-and-eosin-stained sections (10 microns) from 27 Anak (broiler breed) chickens were examined serially, and buds were quantified at 16-20 days of incubation (E) and, posthatch days 1 and 50-60. Taste buds were first recognized at the beginning of E17 as small clusters of cells in the basal epithelium. Only spherical-shaped buds were observed on E17 and E18, and these spherical clusters never penetrated to the surface of the stratified epithelial layer. E19 marked a transitional stage when mature bud features began to emerge: the buds assumed a more elongate shape, several kinds of cells comprising the bud were distinguishable and the first taste pores were observed. During the ensuing embryonic days, buds continued to elongate commensurate with the deepening oral epithelium and by hatching virtually all buds opened to the oral cavity. No marked morphological changes in taste bud structure were observed on the day of hatching and at 50-60 days posthatching. Taste bud numbers increased dramatically during E17 and E18, peaked on E19, and remained relatively constant thereafter. It is concluded that the morphological sequence of taste bud development in chickens is similar to that in mammals. The timing of bud ontogeny, though initiated only during the third trimester in ovo, essentially is completed by hatching, thus providing the precocial hatchling with the sensory apparatus essential for gustatory experience.

Age Factors↗
PubMed1987

Ultrastructure of apical specializations of taste cells in the mudpuppy, Necturus maculosus.

The first interaction of taste stimuli with lingual chemoreceptors occurs on the apical membrane of taste cells, since only that portion is exposed to the oral cavity. To gain better insight into this interaction, we examined the pore region of taste buds in Necturus maculosus with scanning electron microscopy (SEM), transmission electron microscopy, and high-voltage electron microscopy. SEM of the pore reveals a patchwork distribution of three morphologically distinct types of apical specializations: long and branched (LB) microvilli, short and unbranched (SU) microvilli, and bundles of stereocilia. As demonstrated in thin and thick sections, LB microvilli are specializations of dark cells, SU microvilli are the apical specializations of light cells, and stereocilia arise from a cell that has the cytoplasmic markers characteristic of light cells. When left in place, the pore mucus completely covers the SU microvilli and partially covers the LB microvilli. However, stereocilia project above the surface and thus are highly exposed to taste stimuli in the oral cavity. These three morphologically distinct types of apical specializations may reveal functional differences among taste cells. The initial interaction between chemical stimulus and taste cell, and possibly chemoreceptor specificity itself, may be influenced by the morphology of the apical ending.

Animals↗
PubMed1992

Immunocytochemical survey of putative neurotransmitters in taste buds from Necturus maculosus.

To investigate synaptic mechanisms in taste buds and collect information about synaptic transmission in these sensory organs, we have examined taste buds of the mudpuppy, Necturus maculosus for the presence of neurotransmitters and neuromodulators. Immunocytochemical staining at the light microscopic level revealed the presence of serotonin-like and cholecystokinin-like (CCK) immunoreactivity in basal cells in the taste bud. Nerve fibers innervating taste buds were immunoreactive for vasoactive intestinal peptide-like (VIP), substance P-like, and calcitonin gene-related peptide-like (CGRP) or compounds closely related to these substances. Immunoreactivity for tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) in the taste cells and nerve fibers was absent. These data suggest that serotonin, CCK, VIP, substance P, and CGRP are involved in synaptic transmission or neuromodulation in the peripheral organs of taste. No evidence was found for cholinergic or adrenergic mechanisms on the basis of the absence of immunocytochemical staining for key enzymes involved in these two transmitter systems.

Animals↗
PubMed1995

Brain-derived neurotrophic factor mRNA is expressed in the developing taste bud-bearing tongue papillae of rat.

Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are expressed in many areas of the nervous system and its target tissues. Using in situ hybridization we have investigated the possible presence of NGF mRNA and BDNF mRNA in the developing fungiform and circumvallate papillae of the rat tongue. BDNF mRNA is present in the epithelium of the developing fungiform papillae in E15, E16, and E17 rat embryos with peak concentration at E16. It starts to diminish after E17 and is almost absent at E21. There is a specific temporospatial change in the expression of BDNF mRNA in developing circumvallate papillae. It is expressed in the epithelium of the superior and posterior surfaces of the papillae at E15, E16, and E17. Already at E17 the BDNF mRNA labeling has started to decrease in the superior epithelium. At E19 and E21, BDNF mRNA is exclusively present in the epithelium of the inner and outer walls of the trench, surrounding the papilla at the posterior and lateral surfaces where the taste buds are located later in life. BDNF mRNA was also detected in the developing palatal taste buds. NGF mRNA was below detection level in the developing papillae. The highly localized expression of BDNF mRNA in areas where taste buds are to be formed suggests that BDNF may be one crucial factor in the formation of the epithelial innervation prior to taste bud formation. It might also participate in the formation and/or maintenance of the papillary and/or taste bud innervation apparatus. We conclude that the neurotrophin BDNF is expressed in early development of taste bud-bearing papillae in the rat tongue in a temporally and spatially controlled manner, presumably to act as a target-derived chemoattractant for the early nerve fibers.

Animals↗
PubMed2005

Chorda tympani nerve transection at different developmental ages produces differential effects on taste bud volume and papillae morphology in the rat.

Chorda tympani nerve transection (CTX) results in morphological changes to fungiform papillae and associated taste buds. When transection occurs during neonatal development in the rat, the effects on fungiform taste bud and papillae structure are markedly more severe than observed following a comparable surgery in the adult rat. The present study examined the potential "sensitive period" for morphological modifications to tongue epithelium following CTX. Rats received unilateral transection at 65, 30, 25, 20, 15, 10, or 5 days of age. With each descending age at the time of transection, the effects on the structural integrity of fungiform papillae were more severe. Significant losses in total number of taste buds and filiform-like papillae were observed when transection occurred 5-30 days of age. Significant reduction in the number of taste pores was indicated at every age of transection. Another group of rats received chorda tympani transection at 10, 25, or 65 days of age to determine if the time course of taste bud degeneration differed depending on the age of the rat at the time of transection. Taste bud volumes differed significantly from intact sides of the tongue at 2, 8, and 50 days post-transection after CTX at 65 days of age. Volume measurements did not differ 2 days post-transection after CTX at 10 or 25 days of age, but were significantly reduced at the other time points. Findings demonstrate a transitional period throughout development wherein fungiform papillae are highly dependent upon the chorda tympani for maintenance of morphological integrity.

Age Factors↗
PubMedDate not supplied

Sweet and bitter taste: structure and conformations of two aspartame dipeptide analogues.

The synthesis and X-ray diffraction analysis of two dipeptide taste ligands have been carried out as part of our study of the molecular basis of taste. The compounds L-aspartyl-D-alpha-methylphenylalanine methyl ester [L-Asp-D-(alpha Me)Phe-OMe] and L-aspartyl-D-alanyl-2,2,5, 5-tetramethylcyclopentanyl ester [L-Asp-D-Ala-OTMCP] elicit bitter and sweet taste, respectively. The C-terminal residues of the two analogues adopt distinctly different conformations in the solid state. The aspartyl moiety assumes the same conformation found in other dipeptide taste ligands with the side-chain carboxylate and the amino groups forming a zwitterionic ring with a conformation defined by psi, chi 1 = 157.7 degrees, -61.5 degrees for L-Asp-D-Ala-OTMCP and 151.0 degrees, -68.8 degrees for L-Asp-D-(alpha Me)Phe-OMe. In the second residue, a left-handed helical conformation is observed for the (alpha Me)Phe residue of L-Asp-D-(alpha Me)Phe-OMe with phi 2 = 49.0 degrees and psi 2 = 47.9 degrees, while the Ala residue of L-Asp-D-Ala-OTMCP adopts a semi-extended conformation characterized by dihedral angles phi 2 = 62.8 degrees and psi 2 = -139.9 degrees. The solid-state structure of the bitter L-Asp-D-(alpha Me)Phe-OMe is extended: while the crystal structure of the sweet L-Asp-D-OTMCP roughly adopts the typical L-shaped structure shown by other sweeteners. The data of L-Asp-D-(alpha Me)Phe-OMe are compared with those of its diastereoisomer L-Asp-L-(alpha Me)Phe-OMe. Conformational analysis of the two taste ligands in solution by NMR and computer simulations agrees well with our model for sweet and bitter tastes.

Aspartame↗
PubMed1999

Summation of overshadowing and latent inhibition in rats' conditioned taste aversion: scapegoat technique works for familiar meals.

In rats' taste aversion learning, presentation of another taste with a target taste alleviates aversion for the target taste (overshadowing), and exposure of a target taste prior to its conditioning alleviates aversion for that taste (latent inhibition). The present study demonstrated summation of these effects, resulting in the least aversion in the rats that had received both overshadowing and latent inhibition treatments. The finding that overshadowing and latent inhibition summate is contrary to the prediction by the comparator hypothesis that they counteract, as recently reported in conditioned suppression of licking in thirsty rats. The present result supports the employment of the so-called "scapegoat technique" in cancer patients receiving chemotherapy after taking familiar meals.

Analysis of Variance↗
PubMed1987

Receptive field properties of the parabrachio-thalamic taste and mechanoreceptive neurons in rats.

Receptive fields (RFs) of 36 taste (the 22 parabrachio-thalamic relay (P-T) and 14 non-P-T) and 23 mechanoreceptive neurons (7 P-T and 16 non-P-T) were located in the oral cavity of rats. All of the taste and most of the mechanoreceptive units examined had an RF on the ipsilateral side of the tongue or palate, but some mechanoreceptive P-T and non-P-T units had RFs bilaterally. When the RFs of taste neurons were examined with the most effective of the four basic taste (the best stimulus) and non-best stimuli, no difference was noticed in the location of RFs between the P-T and non-P-T neurons. Though most of the P-T neurons (7/11) and all of the non-P-T neurons (6/6) had an RF for non-best stimuli at a region similar to that for the best stimulus, some P-T neurons (4/11) had an RFs for non-best stimulus outside the RF for the best stimulus and/or on the region separate from the RF for the best stimulus. The P-T neurons, responding vigorously to non-optimal stimuli as well as to the best stimulus, had an RF outside the RF for the best stimulus. RFs for mechanical stimulation were also examined in some taste and mechanoreceptive neurons. The mechanoreceptive P-T units rarely had an RF exclusively on the palate. Some mechanoreceptive units had an RF on the region where no taste RF has been found, e.g. the intermolar eminence and the folium of the hard palate.

Afferent Pathways↗
PubMed1990

Keratin filaments of epithelial and taste-bud cells in the circumvallate papillae of adult and developing mice.

Keratin filaments of epithelial- and taste-bud cells in the circumvallate papillae of adult and developing mice were studied by immunocytochemistry using monoclonal antikeratin antibodies (PKK2 and PKK3) and by conventional electron microscopy. Elongated cells (type-I, -II, and -III cells) of the taste buds were stained by PKK3 antibody, which reacts with 45-kdalton keratin, whereas basal cells of the taste buds and surrounding epithelial cells showed negative staining with PKK3. Such PKK3-reactive cells occurred at 0 day after birth, when taste-buds first appeared in the dorsal surface epithelium of the papillae. Thus 45-kdalton keratin seems to be an excellent immunocytochemical marker for identifying taste-bud cells. Epithelial cells in all layers of the trench wall and basal layer cells of the dorsal surface contained densely aggregated bundles of keratin filaments that reacted with PKK2 antibody, but not with PKK3. In contrast, taste-bud cells and spinous and granular layer cells of the dorsal surface possessed loose aggregated bundles of filaments that reacted with PKK3, but not with PKK2. These results suggest that the aggregation and distribution pattern of keratin filaments may reflect differences in the keratin subtypes that comprise these filaments.

Actin Cytoskeleton↗
PubMed1976

Reduction of learned taste aversions by pre-exposure to drugs.

Taste aversions are induced by a variety of psychotropic drugs. In the present experiments taste aversions induced by the barbiturate hypnotic drug, amobarbital, were dramatically reduced by prior exposure to the drug. Increasing numbers of pre-exposures were associated with larger reductions in taste aversions. Reductions in sleeping time (a widely accepted measure of tolerance to barbiturate drugs) were not correlated with reductions in taste aversions. Taste aversions induced by amobarbital were also impaired following pre-exposure to the pharmacologically dissimilar drug d-amphetamine. These results suggest that reduced taste aversions following pre-exposure to drugs may reflect habituation to drug-related stimuli and not solely the development of tolerance to those drugs.

Amobarbital↗
PubMed1989

Separate effects of cigarette smoke yield and smoke taste on smoking behavior.

The purpose of this experiment was to compare independently the influence of different cigarette smoke taste categories and different machine standard smoke yield values on cigarette smoking behavior and related subjective measures. In six separate sessions 15 regular smokers were presented with a medium and a low smoke yield cigarette of each of the three taste categories, mentholated, dark (Gauloises) and blond (Muratti) tobacco. Each session included a "natural" and a "forced" smoking procedure of one cigarette type only. Forced smoking consisted of smoking 30 puffs whereby a new half-length cigarette was presented after every third puff. During the seventh session, habitual brand cigarettes were smoked as a reference. The sessions followed in weekly intervals, and the subjects became familiar with the test cigarettes during the last 5 days preceding each test session. Although general acceptability of the cigarettes, smoking satisfaction and pleasantness of taste were clearly lower for all test cigarettes as opposed to the habitual brand reference cigarettes, these measures remained unaffected by taste or smoke yield of the test cigarettes. Harshness of smoke was higher in the dark tobacco category and generally decreased with the lower smoke yield cigarettes. Independent effects of taste and smoke yield were obtained for total puff volume, inhalation time and CO absorption, suggesting a compensatory intensification of smoking behavior for low yield cigarettes and an independent increase of smoking intensity from mentholated to dark tobacco to blond tobacco. The results suggest therefore that factors which affect cigarette smoke taste have effects on smoking behavior which are separate from those obtained by comparing smoke yields.

Adult↗
PubMed1991

Development of taste organs in Rana temporaria. Transmission and scanning electron microscopic study.

In tadpoles of Rana temporaria two successive generations of taste organs: taste buds (TBs) and taste disks were studied. The TBs are located in the apices of oral premetamorphic papillae. Each TB consists of vertically elongated receptor cells (probably taste) and supporting cells. No basal (Merkel) cells were observed there. Morphologically, two types of receptor cells have been distinguished in a TB. Complete synaptic structures were observed in the TBs between the 30th and 41st of Gosner's (1960) developmental stages, though synaptic vesicles occur already at stage 26. The taste disks consist of taste cells, supporting cells and basal cells. Dense-core synaptic vesicles occur in the gustatory cells at stage 41, but complete synaptic structures were not observed earlier than at stage 45. Synaptic junctions observed at some of the gustatory cells seem to be reciprocal (bidirectional).

Animals↗
PubMed1993

Freeze-fracture characterization of cell types at the surface of the taste organ of the frog, Rana esculenta.

The ultrastructure and distribution of intramembrane particles in the chemoreceptor surface of the frog taste organ have been studied by means of freeze-fracture. Sustentacular, wing, mucous cells and two different types of putative taste cells were found to reach the free surface of this chemoreceptor. Each of these cell types was characterized by a different pattern and density of intramembrane particles in the free surface. Wing cells displayed a relatively low number of large intramembrane particles (11.1 +/- 1.4 nm in diameter). Particles of similar size were also present in a much higher concentration in the membrane of cylinder-ending putative taste cells. In microvilli-ending putative taste cells, mucous cells, and sustentacular cells, small intramembrane particles were observed (6.8 +/- 0.78, 6.9 +/- 1.3, 7.2 +/- 0.7 nm in diameter, respectively). The density of these particles was higher in the sustentacular cells than in the other two cell types. These data provide evidence that there are two morphologically distinct types of putative taste cells in the frog taste organ, demonstrating that they are characterized by different pattern of intramembrane particles in their free surface. Furthermore, the present results support previous findings indicating that wing and sustentacular elements represent two different cell types.

Animals↗