A functional division of Drosophila sweet taste neurons that is value-based and task-specific

Sucrose is an attractive feeding substance and a positive reinforcer for Drosophila. But Drosophila females have been shown to robustly reject a sucrose-containing option for egg-laying when given a choice between a plain and a sucrose-containing option in specific contexts. How the sweet taste system of Drosophila promotes context-dependent devaluation of an egg-laying option that contains sucrose, an otherwise highly appetitive tastant, is unknown. Here, we report that devaluation of sweetness/sucrose for egg-laying is executed by a sensory pathway recruited specifically by the sweet neurons on the legs of Drosophila. First, silencing just the leg sweet neurons caused acceptance of the sucrose option in a sucrose versus plain decision, whereas expressing the channelrhodopsin CsChrimson in them caused rejection of a plain option that was “baited” with light over another that was not. Analogous bidirectional manipulations of other sweet neurons did not produce these effects. Second, circuit tracing revealed that the leg sweet neurons receive different presynaptic neuromodulations compared to some other sweet neurons and were the only ones with postsynaptic partners that projected prominently to the superior lateral protocerebrum (SLP) in the brain. Third, silencing one specific SLP-projecting postsynaptic partner of the leg sweet neurons reduced sucrose rejection, whereas expressing CsChrimson in it promoted rejection of a light-baited option during egg-laying. These results uncover that the Drosophila sweet taste system exhibits a functional division that is value-based and task-specific, challenging the conventional view that the system adheres to a simple labeled-line coding scheme.

Three-dimensional characteristic of fungiform papillae and its taste buds in European bison (Bison bonasus), cattle (Bos taurus), and Bison bonasus hybrid

Background Our recent macro- and scanning electron microscopic study of tongue conducted on domesticated cattle, wild living European bison, and Bison bonasus hybrid revealed various spatial arrangement and number of gustatory and mechanical papillae between parental species and their hybrid. Furthermore, scanning electron microscopy analysis of gustatory papillae indicated the variable distribution of fungiform papillae (Fu) over the surface of the tongue, which could be significant in differentiated taste perception during feeding in studied wild living and domesticated husbandry ruminants. To specify the detailed microstructure of Fu papillae with connective tissue cores (CTC) and intraepithelial taste buds system, the first time the three-dimensional computer-aided analysis of serial histoslides resulted in the rendering of 3D reconstructions of Fu papillae. Results The comparative analysis of 3D models Fu papillae conducted in six areas of lingual mucosa of each tongue revealed information about, microstructural diversity of Fu papillae in studied ruminants. The estimation of number and density of Fu papillae on tongues, rate of protrusion of papillae over mucosa, and a number of taste buds per papilla allowed to state the ventral surface of the lingual apex and posterolateral surfaces of the lingual torus as regions important in taste perception, as in the preselection of taken food, as well in the analysis of food during rumination, respectively. On the 3D models were observed three structural types of CTC of different distribution on the tongue in studied species. The quantitative data of the number of taste buds on Fu papillae have regional functional differences in the taste system important in feeding and veterinary practice. Moreover, our analysis determined specific features in examined hybrid and showed similarities of some studied features with cattle, i.e., maternal species. Conclusions The 3D reconstruction method used for the first time in the field of study of the lingual papillae and taste buds system can be considered as an innovative and effective tool in assessing of the microstructures of Fu papillae, and it could be suitable for further studies of taste system structures in normal and pathological condition.

Optogenetic induction of appetitive and aversive taste memories in Drosophila

Tastes are typically thought to evoke innate appetitive or aversive behaviours, prompting food acceptance or rejection. However, research in Drosophila melanogaster indicates that taste responses can be modified through experience-dependent changes in mushroom body circuits. In this study, we develop a novel taste learning paradigm using closed-loop optogenetics. We find that appetitive and aversive taste memories can be formed by pairing gustatory stimuli with optogenetic activation of sensory or dopaminergic neurons associated with reward or punishment. As with olfactory memories, distinct dopaminergic subpopulations drive the parallel formation of short- and long-term appetitive memories. Long-term memories are protein synthesis-dependent and have energetic requirements that are satisfied by a variety of caloric food sources or by direct stimulation of MB-MP1 dopaminergic neurons. Our paradigm affords new opportunities to probe plasticity mechanisms within the taste system and understand the extent to which taste responses are experience dependent.

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.

Preliminary Research into the Sustainable Responsibility of Teaware Design—A Fs/QCA Analysis of the Influence of the Smell and Taste of Tea through Visual and Tactile Perception

Most studies concerned with sustainable design issues focus on product design to change user behavior, increase the product lifespan, reduce energy waste, or employ the user experience to influence the behavior of other users. Rarely do they discuss how to design products that meet the real needs of consumers and reduce design waste and excessive consumption. Teaware designers and producers have invisibly created a considerable carbon footprint with regard to nonrenewable clay and energy waste due to excessive production. Therefore, this research uses visual and tactile research into the Chinese drinking cup to integrate user experience and the designer’s thinking and methods to ensure the sustainable value of the design and industry. This research uses experimental methods to collect and analyze the data with a fuzzy set qualitative comparative analysis (fs/QCA). The research found that the visual, tactile, and sensory perceptions of general consumers and tea professionals have different influencing factors on the taste system. This research provides evidence that the size of the tea-drinking container and the thickness of the cup’s rim will affect the perception of the tea’s taste and smell. This research provides new thinking for the design of Chinese tea-drinking utensils. It could solve social problems and dilemmas through design and contribute to the sustainable development of the design.

The umami receptor T1R1–T1R3 heterodimer is rarely formed in chickens

The characterization of molecular mechanisms underlying the taste-sensing system of chickens will add to our understanding of their feeding behaviors in poultry farming. In the mammalian taste system, the heterodimer of taste receptor type 1 members 1/3 (T1R1/T1R3) functions as an umami (amino acid) taste receptor. Here, we analyzed the expression patterns of T1R1 and T1R3 in the taste cells of chickens, labeled by the molecular markers for chicken taste buds (vimentin and α-gustducin). We observed that α-gustducin was expressed in some of the chicken T1R3-positive taste bud cells but rarely expressed in the T1R1-positive and T2R7-positive taste bud cells. These results raise the possibility that there is another second messenger signaling system in chicken taste sensory cells. We also observed that T1R3 and α-gustducin were expressed mostly in the vimentin-positive taste bud cells, whereas T1R1 and bitter taste receptor (i.e., taste receptor type 2 member 7, T2R7) were expressed largely in the vimentin-negative taste bud cells in chickens. In addition, we observed that T1R1 and T1R3 were co-expressed in about 5% of chickens' taste bud cells, which express T1R1 or T1R3. These results suggest that the heterodimer of T1R1 and T1R3 is rarely formed in chickens’ taste bud cells, and they provide comparative insights into the expressional regulation of taste receptors in the taste bud cells of vertebrates.

Ghrelin Receptors Enhance Fat Taste Responsiveness in Female Mice

Ghrelin is a major appetite-stimulating neuropeptide found in circulation. While its role in increasing food intake is well known, its role in affecting taste perception, if any, remains unclear. In this study, we investigated the role of the growth hormone secretagogue receptor’s (GHS-R; a ghrelin receptor) activity in the peripheral taste system using feeding studies and conditioned taste aversion assays by comparing wild-type and GHS-R-knockout models. Using transgenic mice expressing enhanced green fluorescent protein (GFP), we demonstrated GHS-R expression in the taste system in relation phospholipase C ß2 isotype (PLCβ2; type II taste cell marker)- and glutamate decarboxylase type 67 (GAD67; type III taste cell marker)-expressing cells using immunohistochemistry. We observed high levels of co-localization between PLCβ2 and GHS-R within the taste system, while GHS-R rarely co-localized in GAD67-expressing cells. Additionally, following 6 weeks of 60% high-fat diet, female Ghsr−/− mice exhibited reduced responsiveness to linoleic acid (LA) compared to their wild-type (WT) counterparts, while no such differences were observed in male Ghsr−/− and WT mice. Overall, our results are consistent with the interpretation that ghrelin in the taste system is involved in the complex sensing and recognition of fat compounds. Ghrelin-GHS-R signaling may play a critical role in the recognition of fatty acids in female mice, and this differential regulation may contribute to their distinct ingestive behaviors.

Neural Coding of Food Is a Multisensory, Sensorimotor Function

This review is a curated discussion of the relationship between the gustatory system and the perception of food beginning at the earliest stage of neural processing. A brief description of the idea of taste qualities and mammalian anatomy of the taste system is presented first, followed by an overview of theories of taste coding. The case is made that food is encoded by the several senses that it stimulates beginning in the brainstem and extending throughout the entire gustatory neuraxis. In addition, the feedback from food-related movements is seamlessly melded with sensory input to create the representation of food objects in the brain.

The mosquito taste system and disease control

Mosquitoes are a widely diverse group of organisms, comprising ∼3,500 species that live in an enormous range of habitats. Some species are vectors of diseases that afflict hundreds of millions of people each year. Although understanding of mosquito olfaction has progressed dramatically in recent years, mosquito taste remains greatly understudied. Since taste is essential to feeding, egg laying, and mating decisions in insects, improved understanding of taste in mosquitoes could provide new mechanistic insight into many aspects of their behavior. We provide a guide to current knowledge in the field, and we suggest a wealth of opportunities for research that are now enabled by recent scientific and technological advances. We also propose means by which taste might be exploited in new strategies for mosquito control, which may be urgently needed as the geographical ranges of vector species increase with climate change.