Circumvallate Taste Buds Research Articles

Death in the taste bud: Morphological features of dying taste cells and engulfment by Type I cells.

Taste buds comprise 50-100 epithelial derived cells, which are renewed throughout the life of an organism. Immature cells enter the bud at its base, maturing into one of three distinct cell types. How taste cells die and/or exit the bud, however, remains unclear. Here we present morphological data obtained through Serial Blockface Scanning Electron Microscopy of murine circumvallate taste buds, revealing several taste cells at the end of their life (4-6 per bud). Cells we identify as dying share certain morphological features typical of apoptosis: swollen endoplasmic reticulum, large lysosomes, degrading organelles, distended outer nuclear membranes, heterochromatin reorganization, cell shrinkage, and cell and/or nuclear fragmentation. Based on these features, we divide the cells into "early" and "late" stage dying cells. Most early stage dying cells have Type II cell morphologies, while a few display Type III cell features. Many dying cells maintain contacts with nerve fibers, but those fibers often appear detached from the main trunk of an afferent nerve fiber. Dying cells, like mature Type II and Type III taste cells, are surrounded by Type I taste cells, the glial-like cells of the bud. In many instances Type I cells appear to be engulfing their dying neighbors, suggesting a novel, phagocytic role for Type I cells. Surprisingly, virtually no Type I cells, which have the shortest residence time in taste buds, display features of apoptosis. The ultimate fate of Type I cells therefore remains enigmatic.

Histopathology of the Tongue in a Hamster Model of COVID-19.

With altered sense of taste being a common symptom of coronavirus disease 2019 (COVID-19), our objective was to investigate the presence and distribution of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) within the tongue over the course of infection. Golden Syrian hamsters were inoculated intranasally with SARS-CoV-2 and tongues were collected at 2, 3, 5, 8, 17, 21, 35, and 42 days post-infection (dpi) for analysis. In order to test for gross changes in the tongue, the papillae of the tongue were counted. Paraffin-embedded thin sections of the tongues were labeled for the presence of SARS-CoV-2 antigen. There was no difference in fungiform or filiform papillae density throughout the course of infection. SARS-CoV-2 antigen was observed in the circumvallate papillae taste buds (3-35 dpi) and autonomic ganglia (5-35 dpi), as well as in the serous and mucous salivary glands of the posterior tongue (2-42 dpi). The presence and distribution of SARS-CoV-2 suggest that the virus could cause taste disturbance by infecting the circumvallate taste buds. This effect could be exacerbated by a diminished secretion of saliva caused by infection of the serous salivary glands and the autonomic ganglia which innervate them.

Cyclophosphamide induces the loss of taste bud innervation in mice.

Many common chemotherapeutics produce disruptions in the sense of taste which can lead to loss of appetite, nutritional imbalance, and reduced quality of life, especially if taste loss persists after treatment ends. Cyclophosphamide (CYP), an alkylating chemotherapeutic agent, affects taste sensitivity through its cytotoxic effects on mature taste receptor cells (TRCs) and on taste progenitor cell populations, retarding the capacity to replace TRCs. Mechanistic studies have focused primarily on taste cells, however, taste signaling requires communication between TRCs and the gustatory nerve fibers that innervate them. Here, we evaluate cyclophosphamide's effects on the peripheral gustatory nerve fibers that innervate the taste buds. Following histological analysis of tongue tissues, we find that CYP reduces innervation within the fungiform and circumvallates taste buds within 4 days after administration. To better understand the dynamics of the denervation process, we used 2-photon intravital imaging to visualize the peripheral gustatory nerve fibers within individual fungiform taste buds up to 20 days after CYP treatment. We find that gustatory fibers retract from the taste bud properly but are maintained within the central papilla core. These data indicate that in addition to TRCs, gustatory nerve fibers are also affected by CYP treatment. Because the connectivity between TRCs and gustatory neurons must be re-established for proper function, gustatory fibers should continue to be included in future studies to understand the mechanisms leading to chemotherapy-induced persistent taste loss.

Ultrastructural localization of calcium homeostasis modulator 1 in mouse taste buds.

Taste receptor cells are morphologically classified as types II and III. Type II cells form a unique type of synapses referred to as channel synapses where calcium homeostasis modulator 1 (CALHM1) together with CALHM3 forms voltage-gated channels that release the neurotransmitter, adenosine triphosphate (ATP). To validate the proposed structural model of channel synapses, the ultrastructural localization of CALHM1 in type II cells of both fungiform and circumvallate taste buds was examined. A monoclonal antibody against CALHM1 was developed and its localization was evaluated via immunofluorescence and immunoelectron microscopy using the immunogold-silver labeling technique. CALHM1 was detected as puncta using immunofluorescence and along the presynaptic membrane of channel synapses facing atypical mitochondria, which provide ATP, by immunoelectron microscopy. In addition, it was detected along the plasma membrane lined by subsurface cisternae at sites apposed to afferent nerve fibers. Our results support the validity of a previously proposed structural model for channel synapses and provide insights into the function of subsurface cisternae whose function in taste receptor cells is unknown. We also examined the localization of CALHM1 in hybrid synapses of type III cells, which are conventional chemical synapses accompanied by mitochondria similar to atypical mitochondria of channel synapses. CALHM1 was not detected in the six hybrid synapses examined using immunoelectron microscopy. We further performed double immunolabeling for CALHM1 and Bassoon, which is detected as puncta corresponding to conventional vesicular synapses in type III cells. Our observations suggest that at least some, and probably most, hybrid synapses are not accompanied by CALHM1.

The duct of von Ebner's glands is a source of Sox10 + taste bud progenitors and susceptible to pathogen infections.

We have recently demonstrated that Sox10-expressing (Sox10 +) cells give rise to mainly type-III neuronal taste bud cells that are responsible for sour and salt taste. The two tissue compartments containing Sox10 + cells in the surrounding of taste buds include the connective tissue core of taste papillae and von Ebner's glands (vEGs) that are connected to the trench of circumvallate and foliate papillae. In this study, we performed single cell RNA-sequencing of the epithelium of Sox10-Cre/tdT mouse circumvallate/vEG complex and used inducible Cre mouse models to map the cell lineages of vEGs and/or connective tissue (including stromal and Schwann cells). Transcriptomic analysis indicated that Sox10 expression was enriched in the cell clusters of vEG ducts that contained abundant proliferating cells, while Sox10-Cre/tdT expression was enriched in type-III taste bud cells and vEG ductal cells. In vivo lineage mapping showed that the traced cells were distributed in circumvallate taste buds concurrently with those in the vEGs, but not in the connective tissue. Moreover, multiple genes encoding pathogen receptors were enriched in the vEG ducts hosting Sox10 + cells. Our data supports that it is the vEGs, not connective tissue core, that serve as the niche of Sox10 + taste bud progenitors. If this is also true in humans, our data indicates that vEG duct is a source of Sox10 + taste bud progenitors and susceptible to pathogen infections.

The Influence of Roux-en-Y Gastric Bypass and Diet on NaCl and Sucrose Taste Detection Thresholds and Number of Circumvallate and Fungiform Taste Buds in Female Rats.

Roux-en-Y gastric bypass (RYGB) in rats attenuates preference for, and intake of, sugar solutions. Additionally, maintenance on a high-fat diet (HFD) reportedly alters behavioral responsiveness to sucrose in rodents in short-term drinking tests. Due to the fact that the behavioral tests to date rely on the hedonic value of the stimulus to drive responsiveness, we sought to determine whether taste detection thresholds to sucrose and NaCl are affected by these manipulations as measured in an operant two-response signal detection paradigm. Female rats were maintained on HFD or chow for 10 weeks, at which point animals received either RYGB or SHAM surgery followed by a gel-based diet and then powdered chow. Upon recovery, half of the rats that were previously on HFD were switched permanently to chow, and the other rats were maintained on their presurgical diets (n = 5–9/diet condition × surgery group for behavioral testing). The rats were then trained and tested in a gustometer. There was a significant interaction between diet condition and surgery on NaCl threshold that was attributable to a lower value in RYGB vs. SHAM rats in the HFD condition, but this failed to survive a Bonferroni correction. Importantly, there were no effects of diet condition or surgery on sucrose thresholds. Additionally, although recent evidence suggests that maintenance on HFD alters taste bud number in the circumvallate papillae (CV) of mice, in a subset of rats, we did not find that diet significantly influenced taste pores in the anterior tongue or CV of female rats. These results suggest that any changes in sucrose responsiveness in intake/preference or hedonically oriented tests in rats as a function of HFD maintenance or RYGB are not attributable to alterations in taste sensitivity.

The presynaptic active zone protein Bassoon as a marker for synapses between Type III cells and afferent nerve fibers in taste buds.

Taste buds are receptor organs for gustation. Two types of taste receptor cells have been identified in taste buds: Type II and Type III cells. Type III cells connect with afferent fibers through conventional chemical synapses. In the present study, we used immunocytochemistry to examine the distribution pattern of Bassoon, a scaffolding protein of the cytomatrix at the active zones of conventional synapses in mouse taste buds. Bassoon was predominantly detected as small puncta in Type III cells. Bassoon-immunoreactive puncta were observed in proximity to or partially overlapping with intragemmal nerve fibers. The distribution pattern of Bassoon in taste buds was similar among circumvallate, fungiform, and foliate taste buds. Immunoelectron microscopy showed Bassoon at the active zones of the conventional synapses of Type III cells in circumvallate taste buds. The present results demonstrate that Bassoon is a marker for synapses between Type III cells and afferent fibers in mouse taste buds.

Taste Bud Connectome: Implications for Taste Information Processing.

Taste buds contain multiple cell types, two of which mediate transduction of specific taste qualities: Type III cells transduce sour while Type II cells transduce either sweet, or bitter or umami. In order to discern the degree of interaction between different cell types and specificity of connectivity with the afferent nerve fibers (NFs), we employed serial blockface scanning electron microscopy (sbfSEM) through five circumvallate mouse taste buds. Points of contact between Type II and Type III cells are rare and lack morphologically identifiable synapses, suggesting that interaction between these cell types does not occur via synapses. Of the 127 NFs that make synaptic contacts with taste cells in the sampling volume, ∼70% (n = 91) synapse with only one taste cell while 32 fibers synapse exclusively with multiple Type II cells or multiple Type III cells. Our data do not rule out multimodal fibers innervating Type II cells of separate taste qualities. Notably, four fibers (∼3%) synapse with both Type II and Type III cells, forming both mitochondrial and vesicular synapses on the different cell types. Since Type II and Type III cells transduce different taste qualities, these dual connected fibers are not consistent with a absolute labeled-line encoding system. Further, our data reveal considerable variation in both the number of synapses per cell/nerve pair and the number of innervating NFs per taste cell, both of which likely have consequences for encoding taste quality and concentration. Finally, we identify a subset of Type II cells which may represent an immature stage.SIGNIFICANCE STATEMENT Taste buds, the sensory end organs for the sense of taste, contain multiple types of sensory cells, with each responding to one of the primary tastes: salt, sweet, sour, bitter, and umami. In order to determine the degree of interaction between cell types and specificity of connectivity to afferent nerves, we employed serial blockface electron microscopy (EM) of mouse circumvallate taste buds. We find no synapses between cell types within the taste bud suggesting that any interactions are indirect. While the majority of nerve fibers (NFs) connect to a single type of taste cell, 3.1% of the fibers branch to receive input from taste cells of different specificities. Thus, taste cannot entirely be carried along NFs dedicated to single taste qualities.

Sprague Dawley Rats Gaining Weight on a High Energy Diet Exhibit Damage to Taste Tissue Even after Return to a Healthy Diet.

Many reports detail taste dysfunction in humans and animals with obesity. For example, mice consuming an obesogenic diet for a short period have fewer taste buds than their lean littermates. Further, rats with diet-induced obesity (DIO) show blunted electrophysiological responses to taste in the brainstem. Here, we studied the effects of high energy diet (HED)-induced peripheral taste damage in rats, and whether this deficiency could be reversed by returning to a regular chow diet. Separate groups of rats consumed a standard chow diet (Chow), a HED for 10 weeks followed by a return to chow (HED/chow), or a HED for 10 weeks followed by a restricted HED that was isocaloric with consumption by the HED/chow group (HED/isocal). Fungiform taste papilla (FP) and circumvallate taste bud abundance were quantified several months after HED groups switched diets. Results showed that both HED/chow and HED/isocal rats had significantly fewer FP and lower CV taste bud abundance than control rats fed only chow. Neutrophil infiltration into taste tissues was also quantified, but did not vary with treatment on this timeline. Finally, the number of cells undergoing programmed cell death, measured with caspase-3 staining, inversely correlated with taste bud counts, suggesting taste buds may be lost to apoptosis as a potential mechanism for the taste dysfunction observed in obesity. Collectively, these data show that DIO has lasting deleterious effects on the peripheral taste system, despite a change from a HED to a healthy diet, underscoring the idea that obesity rather than diet predicts damage to the taste system.

Whole-Mount Staining, Visualization, and Analysis of Fungiform, Circumvallate, and Palate Taste Buds.

Taste buds are collections of taste-transducing cells specialized to detect subsets of chemical stimuli in the oral cavity. These transducing cells communicate with nerve fibers that carry this information to the brain. Because taste-transducing cells continuously die and are replaced throughout adulthood, the taste-bud environment is both complex and dynamic, requiring detailed analyses of its cell types, their locations, and any physical relationships between them. Detailed analyses have been limited by tongue-tissue heterogeneity and density that have significantly reduced antibody permeability. These obstacles require sectioning protocols that result in splitting taste buds across sections so that measurements are only approximated, and cell relationships are lost. To overcome these challenges, the methods described herein involve collecting, imaging, and analyzing whole taste buds and individual terminal arbors from three taste regions: fungiform papillae, circumvallate papillae, and the palate. Collecting whole taste buds reduces bias and technical variability and can be used to report absolute numbers for features including taste-bud volume, total taste-bud innervation, transducing-cell counts, and the morphology of individual terminal arbors. To demonstrate the advantages of this method, this paper provides comparisons of taste bud and innervation volumes between fungiform and circumvallate taste buds using a general taste-bud marker and a label for all taste fibers. A workflow for the use of sparse-cell genetic labeling of taste neurons (with labeled subsets of taste-transducing cells) is also provided. This workflow analyzes the structures of individual taste-nerve arbors, cell type numbers, and the physical relationships between cells using image analysis software. Together, these workflows provide a novel approach for tissue preparation and analysis of both whole taste buds and the complete morphology of their innervating arbors.

Whole-Mount Staining, Visualization, and Analysis of Fungiform, Circumvallate, and Palate Taste Buds

Whole-Mount Staining, Visualization, and Analysis of Fungiform, Circumvallate, and Palate Taste Buds

SOX10-Cre-Labeled Cells Under the Tongue Epithelium Serve as Progenitors for Taste Bud Cells That Are Mainly Type III and Keratin 8-Low.

Taste bud cells are specialized epithelial cells that undergo continuous turnover, and thus require active progenitors for their renewal and an intact taste function. Our previous studies suggested that a population of taste bud cells originates from outside of the surrounding tongue epithelium-previously regarded sole source of taste bud progenitors. In this study, we demonstrated that SOX10 (SRY-related HMG-box gene 10)-expressing cells, known to be in the migrating neural crest, were also distributed in taste bud-surrounding tissue compartments under the tongue epithelium, that is, the connective tissue core of taste papillae and von Ebner's glands. By lineage tracing of SOX10-expressing cells using SOX10-Cre, a Cre model driven by the endogenous SOX10 promoter, crossing with a Cre reporter line R26-tdTomato (tdT), we found SOX10-Cre-labeled tdT+ cells within taste buds in all three types of taste papillae (fungiform, circumvallate, and foliate) as well as in the soft palate in postnatal mice. The tdT+ taste bud cells were progressively more abundant along the developmental stages, from virtually zero at birth to over 35% in adults. Most of tdT+ taste bud cells had a low intensity of immunosignals of Keratin 8 (a widely used taste bud cell marker). In circumvallate taste buds, tdT signals were co-localized principally with a type III taste bud cell marker, less so with type I and II cell makers. Together, our data demonstrate a novel progenitor source for taste buds of postnatal mice-SOX10-Cre-labeled cells in the connective tissue core and/or von Ebner's glands.

Quantitative Analysis of Taste Bud Cell Numbers in the Circumvallate and Foliate Taste Buds of Mice.

A mouse single taste bud contains 10-100 taste bud cells (TBCs) in which the elongated TBCs are classified into 3 cell types (types I-III) equipped with different taste receptors. Accordingly, differences in the cell numbers and ratios of respective cell types per taste bud may affect taste-nerve responsiveness. Here, we examined the numbers of each immunoreactive cell for the type II (sweet, bitter, or umami receptor cells) and type III (sour and/or salt receptor cells) markers per taste bud in the circumvallate and foliate papillae and compared these numerical features of TBCs per taste bud to those in fungiform papilla and soft palate, which we previously reported. In circumvallate and foliate taste buds, the numbers of TBCs and immunoreactive cells per taste bud increased as a linear function of the maximal cross-sectional taste bud area. Type II cells made up approximately 25% of TBCs irrespective of the regions from which the TBCs arose. In contrast, type III cells in circumvallate and foliate taste buds made up approximately 11% of TBCs, which represented almost 2 times higher than what was observed in the fungiform and soft palate taste buds. The densities (number of immunoreactive cells per taste bud divided by the maximal cross-sectional area of the taste bud) of types II and III cells per taste bud are significantly higher in the circumvallate papillae than in the other regions. The effects of these region-dependent differences on the taste response of the taste bud are discussed.

Three-dimensional reconstructions of mouse circumvallate taste buds using serial blockface scanning electron microscopy: I. Cell types and the apical region of the taste bud.

Taste buds comprise four types of taste cells: three mature, elongate types, Types I-III; and basally situated, immature postmitotic type, Type IV cells. We employed serial blockface scanning electron microscopy to delineate the characteristics and interrelationships of the taste cells in the circumvallate papillae of adult mice. Type I cells have an indented, elongate nucleus with invaginations, folded plasma membrane, and multiple apical microvilli in the taste pore. Type I microvilli may be either restricted to the bottom of the pore or extend outward reaching midway up into the taste pore. Type II cells (aka receptor cells) possess a large round or oval nucleus, a single apical microvillus extending through the taste pore, and specialized "atypical" mitochondria at functional points of contact with nerve fibers. Type III cells (aka "synaptic cells") are elongate with an indented nucleus, possess a single, apical microvillus extending through the taste pore, and are characterized by a small accumulation of synaptic vesicles at points of contact with nerve fibers. About one-quarter of Type III cells also exhibit an atypical mitochondrion near the presynaptic vesicle clusters at the synapse. Type IV cells (nonproliferative "basal cells") have a nucleus in the lower quarter of the taste bud and a foot process extending to the basement membrane often contacting nerve processes along the way. In murine circumvallate taste buds, Type I cells represent just over 50% of the population, whereas Types II, III, and IV (basal cells) represent 19, 15, and 14%, respectively.

The prospective role of mesenchymal stem cells exosomes on circumvallate taste buds in induced Alzheimer’s disease of ovariectomized albino rats: (Light and transmission electron microscopic study)

ObjectiveTo elucidate the effect of Alzheimer’s disease on the structure of circumvallate papilla taste buds and the possible role of exosomes on the taste buds in Alzheimer’s disease. DesignForty two ovariectomized female adult albino rats were utilized and divided into: Group I: received vehicle. Group II: received aluminum chloride to induce Alzheimer’s disease. Group III: after the induction of Alzheimer’s disease, each rat received single dose of exosomes then left for 4 weeks. The circumvallate papillae were prepared for examination by light and transmission electron microscope. Statistical analysis: histomorphometric data were statistically analyzed. ResultsHistological examination of circumvallate papilla in Group I showed normal histological features. Group II revealed distorted features. Group III illustrated nearly normal histological features of circumvallate. Silver impregnation results showed apparently great number of heavily impregnated glossopharyngeal nerve fibers in both Groups I & III but markedly decreased in Group II. Synaptophysin-immunoreactivity was strong in Group I, mild in Group II and moderate in Group III. The ultra-structural examination of taste bud cells revealed normal features in Group I, distorted features in Group II and almost normal features in Group III. Statistically highest mean of Synaptophysin-immunoreactivity area% was for Group I, followed by Group III, and the least value was for Group II. ConclusionsAlzheimer’s disease has degenerative effects. Bone marrow mesenchymal stem cell (BM-MSC)-derived exosomes have the ability to improve the destructive changes induced by Alzheimer’s disease.

Nogo receptor (NgR) – signalling is required for the maintenance of the structural integrity of mouse fungiform and circumvallate taste buds

Nogo receptor (NgR) – signalling is required for the maintenance of the structural integrity of mouse fungiform and circumvallate taste buds

Taste loss with obesity in mice and men

Our sense of taste is critical in defining our food choices and habits. Located primarily in our tongue, taste buds are small assemblies of constantly renewing sensory cells, tasked with evaluating oral stimuli before the food we eat is consumed. Using both mice and a free-living human population, we tracked taste papilla abundancy with weight gain, to test for deficiencies in the taste system of obese mice and humans with increased adiposity. Mice fed a high-fat diet for 8 weeks expressed markers for all subtypes of taste cells at a lower level than chow-fed counterparts. This came alongside the loss of markers for taste cell proliferation (Ki-67) and development (β-catenin), as well as lower fungiform papillae density, consistent with earlier results showing lower circumvallate taste bud abundance in obese mice. Likewise, in a population of college students tracked through 4 years of college attendance, the change in density of fungiform papillae, which house taste buds in the anterior tongue, was negatively correlated with change in neck circumference, a marker of adiposity. These results highlight changes in taste during weight gain as a potentially important consideration in the study of obesity.

Taste Receptor Cells in Mice Express Receptors for the Hormone Adiponectin.

The metabolic hormone adiponectin is secreted into the circulation by adipocytes and mediates key biological functions, including insulin sensitivity, adipocyte development, and fatty acid oxidation. Adiponectin is also abundant in saliva, where its functions are poorly understood. Here we report that murine taste receptor cells (TRCs) express specific adiponectin receptors and may be a target for salivary adiponectin. This is supported by the presence of all three known adiponectin receptors in transcriptomic data obtained by RNA-seq analysis of purified circumvallate (CV) taste buds. As well, immunohistochemical analysis of murine CV papillae showed that two adiponectin receptors, ADIPOR1 and T-cadherin, are localized to subsets of TRCs. Immunofluorescence for T-cadherin was primarily co-localized with the Type 2 TRC marker phospholipase C β2, suggesting that adiponectin signaling could impact sweet, bitter, or umami taste signaling. However, adiponectin null mice showed no differences in behavioral lick responsiveness compared with wild-type controls in brief-access lick testing. AAV-mediated overexpression of adiponectin in the salivary glands of adiponectin null mice did result in a small but significant increase in behavioral lick responsiveness to the fat emulsion Intralipid. Together, these results suggest that salivary adiponectin can affect TRC function, although its impact on taste responsiveness and peripheral taste coding remains unclear.

Alterations in the gustatory papillae after anterior bite plate insertion in growing rats.

OBJECTIVES:To determine whether the modification of dental occlusion, without molar extraction, affected the gustatory papillae located in the tongue of growing rats.MATERIALS AND METHODS:Five-week-old male Wistar rats were randomly divided into an anterior bite plate (ABP) group and a control group. Under general anesthesia, ABPs were placed on the occlusal surfaces of the maxillary incisors, while metal caps covered the mandibular incisal edges of the rats in the ABP group. The control group rats underwent a sham operation. The rats in both groups were euthanized 14 days after the procedure. The circumvallate papillae and taste buds were analyzed by immunohistochemical methods, and the fungiform papillae were observed and counted after immersion of the tongue in 1% methylene blue.RESULTS:Two weeks after ABP insertion and mandibular incisal cap placement, the gustatory papillae exhibited morphological and structural changes. The rats in the ABP group had exhibited significantly fewer fungiform papillae, and narrower circumvallate papillae, with greater trench depths, larger trench profile areas, smaller taste bud profile areas, lower ratios of the taste bud profile area to the trench profile area, and more taste buds than those in the control group.CONCLUSIONS:Our findings support the association between occlusal and taste functions and provide a basis for further studies on the gustatory function. In conclusion, loss of molar occlusion, resulting from the ABP and metal cap insertion, altered the peripheral gustatory receptors in the growing rats.

A role for scavenger receptor B1 as a captor of specific fatty acids in taste buds of circumvallate papillae.

Class B scavenger receptor family members, scavenger receptor B1 (SR-B1) and cluster of differentiation 36 (CD36), are broadly expressed cell-surface proteins, both of which are believed to serve as multifaceted players in lipid and lipoprotein metabolism in mammals. Because of its presence in the apical part of taste receptor cells within circumvallate taste buds and its ability to recognise long-chain fatty acids, CD36 has been believed to participate in the sensing of the lipid species within the oral cavity. However, there have been no attempts to address whether SR-B1 has such a role to date. In this study, by reverse transcription- polymerase chain reaction analysis, we detected SR-B1 mRNA in a total RNA sample isolated from the circumvallate papillae of mouse tongue. Immunohistochemical analysis of tongue sections from the animals revealed the expression of SR-B1 protein in a population of taste bud cells of circumvallate papillae. In addition, the pattern of staining in the papillae for SR-B1 agreed closely with that for CD36 in double immunostaining analysis. We performed a cell-free in-vitro assay utilising a peptide mimic of SR-B1 and provided evidence that the receptor could recognise certain of the unsaturated long-chain fatty acids such as oleic acid. Our present findings suggest an additional role for SR-B1 as a captor of specific fatty acids in the oral cavity of mammals and contribute to expanding our knowledge of the physiological function of the receptor.