Chemical Senses最新文献

Liking and disgust are the primary positive and negative emotions, respectively, and are crucial for nutrient intake and toxin avoidance. These emotions are induced by multimodal stimuli, such as taste, olfactory, and somatosensory inputs, and their dysregulation is evident in various psychiatric disorders. To understand the biological basis of liking and disgust, it is crucial to establish an animal model that allows for quantitative estimation of liking and disgust in response to multimodal stimuli. The only readout shared by many species, including humans, for liking and disgust, has been taste reactivity. However, readouts of non-taste stimuli-induced emotions remain unestablished. Here, we show that intraoral administration of capsaicin, a chemosomatosensory stimulus, elicits orofacial and bodily reactions in male mice similar to those observed in taste reactivity. Capsaicin-induced liking reactions at low concentrations and disgust reactions at high concentrations. Capsaicin-induced disgust reactions consisted of various reactions, including gape and forelimb flail, with the proportion of each reaction among the disgust reactions being similar to that induced by bitter and sour stimuli. These findings indicate that orofacial and bodily reactions, defined as taste reactivity, are elicited not only by taste stimuli but also by intraoral chemosomatosensory stimuli. Understanding the biological basis of capsaicin-induced orofacial and bodily reactions will advance our understanding of the fundamental mechanisms underlying liking and disgust across sensory modalities.

In mammals, olfactory communication between conspecifics is crucial in modulating reproductive function. In anestrous does (i.e. female goats), exposure to hair from sexually active bucks (SAB, i.e. male goats) triggers a luteinizing hormone response that may induce ovulation, the "male effect." However, the chemicals in buck hair responsible for this effect and the sensory pathways used by the females to detect this information remain insufficiently understood. In this study, we investigated whether sensory cells from the main olfactory epithelium (MOE) and the vomeronasal organ (VNO) of does respond differently to olfactory stimuli from SAB versus wethers (CAS, i.e. castrated bucks) and how this response is influenced by the female reproductive status (breeding season, anestrous, or ovariectomized (OVX)). To explore this possibility, we stimulated freshly dissociated cells of MOE and VNO cells with chloroform/methanol and aqueous extractions from buck hair, and we assessed cell activation using calcium imaging. Regardless of the extraction method, we observed more cells activated by SAB hair compounds than by those from CAS males. More MOE cells from anestrous were activated by both chloroform and aqueous extracts from SAB than MOE cells from breeding season, or OVX does. Most of these responses originated from non-mature olfactory neurons. These findings suggest that females can discriminate buck sexual activity through sensory detection by the MOE and VNO. The increased response in the MOE to SAB hair compounds during the anestrous period suggests that the MOE may play a more significant role in the "male effect" during this period.

Mice are commonly used for laboratory research, due in large part to the widespread advancement in the genetic toolbox, such as reporters, knock-in, and knockout mice. The effects of aging on the taste system in mice have been largely unstudied. The aim of this study was to examine whether taste preferences to sucrose, NaCl, and NH4Cl were associated with aging and changes in ultrastructural characteristics of fungiform taste pores using scanning electron microscopy. Thirty-minute 2-bottle preference tests in wild-type mice indicated that preferences for NaCl and NH4Cl, but not sucrose, were significantly different in aged mice (16 to 17 months old) relative to young mice (5 months old). In the same animals, we found that the percentage of fungiform papilla with taste pores present was significantly reduced in the aged group. These findings are consistent with our recent study in rats, where aging had a significant impact on chorda tympani nerve responses to salt and ultrastructural characteristics of fungiform taste pores. Collectively, these data suggest that aging significantly affects fungiform taste pore morphology and has a significant impact on taste processing. Future studies investigating the factors that form and maintain taste pores are of critical importance as the pore is necessary for taste stimuli access to taste bud cells.

The mammalian olfactory system enables the detection of a wide variety of chemical compounds via the expression of a repertoire of olfactory receptors comprising the largest gene family in the mammalian genome. Olfactory sensory neurons (OSNs) each express only 1 odorant receptor (OR) gene. In mice, this requires activation of 1 OR gene and repression of over 1,400 other OR genes. In this review, we describe the mechanisms that support the transcription of OR genes and how these mechanisms impact which OR is expressed in each neuron. First, we discuss what is currently known about the role of transcription in OR choice. We then describe the role of specific features of OR genes and enhancers in the regulation of OR transcription. Finally, we discuss characteristics of OSNs which specify transcription of some OR genes while restricting the transcription of others.

Cronkhite-Canada syndrome (CCS) is a very rare gastrointestinal disorder with ectodermal abnormalities. Taste abnormalities appear in more than 80% of cases. Our objective was to investigate the characteristics of CCS. Ten patients with taste abnormalities who were diagnosed with CCS were included. A medical interview, examination of the tongue findings, and blood tests were performed, and taste functions were assessed using an electrogustometry (EGM) and a filter paper disc (FPD) before and after treatment. There was nail atrophy in all cases, weight loss in 8 cases, hair loss in 6 cases, skin hyperpigmentation in 5 cases, gastrointestinal symptoms in 4 cases, and atrophy of the lingual papillae in at least 8 cases. Zinc therapy for taste disorders by the previous physicians was ineffective in all cases. The results of the FPD at the first examination showed a severe decrease in taste function of the anterior tongue, whereas taste function tended to be preserved in the posterior tongue (P < 0.01, Wilcoxon). In all cases, subjective symptoms improved within 3 mo after treatment of CCS. Taste function improved significantly after treatment (FPD in anterior tongue, P < 0.05, EGM in posterior tongue, P < 0.01, Wilcoxon). Taste disorder in CCS tended to be severe in the anterior tongue with findings of tongue papillary atrophy, which appears to be an ectodermal abnormality. Their taste function improved along with symptoms after treatment. The taste tests were useful for determining the effect of treatment for CCS.

Gustatory dysfunction is an often overlooked symptom in people with multiple sclerosis (PwMS), potentially leading to poor appetite, malnutrition, weight loss, and decreased quality of life. This systematic review and meta-analysis aimed to assess the pooled prevalence of gustatory dysfunction in PwMS and compare their gustatory test scores with healthy controls. An online database search of PubMed, Embase, Scopus, and Web of Science was conducted on 2024 June 29. Observational studies reporting gustatory dysfunction or gustatory test scores in PwMS were included. Pooled prevalence rates were calculated using a random-effects model, with subgroup analyses based on the type of gustatory test used. Standardized mean differences (SMD) were calculated for comparisons between PwMS and healthy controls. A total of 9 studies encompassing 1385 PwMS were included. The pooled prevalence of gustatory dysfunction among PwMS was 16.4% (95% confidence intervals [95% CI]: 8.7% to 24.1%, I² = 90%, P < 0.01). Subgroup analysis showed a prevalence of 18.8% (95% CI: 10.5% to 27.2%, I² = 0%) in 4 studies using the Taste Strip Test (TST), while 3 non-TST studies using liquid tastants or self-reports reported a prevalence of 20.2% (95% CI: 7.2% to 33.3%, I² = 86%). PwMS had significantly lower gustatory test scores compared to healthy controls (SMD: -0.93, 95% CI: -1.20 to -0.65, I² = 0%, P = 0.48). Gustatory dysfunction affects a notable proportion of PwMS, with prevalence rates varying by assessment method. Future studies should assess the possible causes of gustatory dysfunction in PwMS using validated gustatory assessment scales.

Many animals transmit information in the form of chemical signals to modify behavior or induce physiological change in receivers. For some taxa, such as species in the order Carnivora, chemical signals are known to provide a critical mode of communication, although they are still poorly understood compared to other signal modalities. Here, we review the literature to identify and categorize potential chemical signals within the Carnivora with a view to determining commonalities based on sex, taxon, and function. Data were drawn from 112 publications, dating from 1896 to 2021. Of the 1,532 discrete chemicals identified, 169 were detected in > 5 species, with 58 found in ≥ 10 species. However, multiple different names were often used to report the same compound, reducing the transparency of the literature. Two hundred and fifty-two chemicals were identified as biomarkers, i.e. associated with specific behavioral contexts (dominance hierarchy, appeasement, agonistic, etc.) or specific demographic traits (age, sex, etc.). Few studies established a causal link between these biomarkers and behavioral or physiological changes, so only a few could be definitively described as behaviorally functional bioactive signals. We found high variability concerning which species, chemicals, and sources were represented in the literature, which could potentially lead to a perceptual bias in the relative importance of certain chemicals. Finally, we propose a method for standardized reporting of chemical signals and suggest that future work should focus on a more consistent expansion of the range of species, products, and chemical types analyzed so that the phylogenetic relationship of chemical signals across taxa can be determined.

In the nasal cavity, olfactory receptor neurons are situated in the sensory epithelium and act to transduce odor signals, whereas the respiratory epithelium is responsible for removing unwanted particles from inhaled air. Although several molecular markers have been identified to define multiple specific cell types in the sensory epithelium, less is known to indicate cells in the respiratory domain. We have recently shown that the non-visual photoreceptor opsin 3 (Opn3) is expressed in the developing olfactory region. This raised the question as to which functional role/s Opn3 might play in the nasal epithelium, as well as whether other non-visual photoreceptors may be expressed in this region. By using Opn3-eGFP and Opn5-tdTomato reporter mice in combination with Foxj1, Ker8, OMP, Sox2, and Tubb3 immunohistochemistry analyzes, our findings show that Opn3 is restricted to the olfactory sensory domain from early embryonic stages, whereas Opn5 is up-regulated in the respiratory epithelium at later developmental stages. In adulthood, Opn3 is expressed in Sox2/Ker8-positive sustentacular cells in the sensory epithelium, whereas Opn5 expression remains in the respiratory epithelium, thus indicating that these molecular markers could be used to distinguish the sensory versus respiratory epithelia. Studies of morphology and expression patterns of Foxj1, Ker8, OMP, Sox2, and Tubb3 in adult Opn3-/- and Opn5-/- mice did not reveal differences from wild-type mice. In addition, neither Opn3-/- nor Opn5-/- mice exhibited a disturbance in olfaction compared to wild-type littermates when performing a buried food test.

Many species of animals rely on their chemical senses to detect tastants and odorants to guide dietary selection, avoid danger, and modulate social interactions, all of which ultimately enhance survival and fitness. Significant progress has been made in our understanding of the 2 major chemosensory systems, taste and smell, through studies in model organisms such as flies and mice, ranging from receptor identification to sensory coding mechanisms. These topics have been extensively reviewed elsewhere. Here, we will instead focus on less commonly used model systems and companion animals, examining how taste receptors have been shaped by feeding ecology over the course of evolution to illustrate the concept that each species lives in its own sensory world, finely tuned to its ecological niche.

We present a new method for fully self-administered olfactory testing. Technical development and testing and 2 user studies were conducted to test the functionality of a prototype device called Automated Olfactory Threshold Test (AutomOT). Technical testing showed repeatable functioning of the developed olfactory display technology in accurately producing 11 predefined odor intensity levels over 10 different days. In User Study 1, we tested the reliability, usability, and subjective workload of the use of the device. Participants (N = 29) with a normal sense of smell performed an automated threshold test 4 times. The results showed that the correlations between the tests were statistically significant, r = 0.44 to 0.78, all P-values ≤0.018. In User Study 2, we demonstrated the functioning of the device with normosmic and hyposmic/anosmic participants (n = 23 and n = 27, respectively) who performed both the current clinical standard, Sniffin' Sticks test, and the AutomOT test. Also, the usability and subjective workload of the use of the device were evaluated. The overall correlation of olfactory thresholds between the Sniffin' Sticks and the AutomOT was r = 0.48, P < 0.001. In both user studies, the results indicated good usability as measured by the System Usability Scale and low workload assessed by NASA Task Load Index. Overall, the results suggest that the newly developed AutomOT test is a reliable, valid, and usable tool for clinical assessment of olfactory thresholds.