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McKellar CE, Siwanowicz I, Dickson BJ, Simpson JH. Controlling motor neurons of every muscle for fly proboscis reaching. eLife 2020; 9:e54978. [PMID: 32584254 PMCID: PMC7316511 DOI: 10.7554/elife.54978] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 06/07/2020] [Indexed: 12/31/2022] Open
Abstract
We describe the anatomy of all the primary motor neurons in the fly proboscis and characterize their contributions to its diverse reaching movements. Pairing this behavior with the wealth of Drosophila's genetic tools offers the possibility to study motor control at single-neuron resolution, and soon throughout entire circuits. As an entry to these circuits, we provide detailed anatomy of proboscis motor neurons, muscles, and joints. We create a collection of fly strains to individually manipulate every proboscis muscle through control of its motor neurons, the first such collection for an appendage. We generate a model of the action of each proboscis joint, and find that only a small number of motor neurons are needed to produce proboscis reaching. Comprehensive control of each motor element in this numerically simple system paves the way for future study of both reflexive and flexible movements of this appendage.
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Affiliation(s)
- Claire E McKellar
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
- Princeton Neuroscience Institute, Princeton UniversityPrincetonUnited States
| | - Igor Siwanowicz
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
| | - Barry J Dickson
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
- Queensland Brain Institute, University of QueenslandSt LuciaAustralia
| | - Julie H Simpson
- Janelia Research Campus, Howard Hughes Medical InstituteAshburnUnited States
- Dept. of Molecular Cellular and Developmental Biology, University of California Santa BarbaraSanta BarbaraUnited States
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2
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Kaushik S, Kumar R, Kain P. Salt an Essential Nutrient: Advances in Understanding Salt Taste Detection Using Drosophila as a Model System. J Exp Neurosci 2018; 12:1179069518806894. [PMID: 30479487 PMCID: PMC6249657 DOI: 10.1177/1179069518806894] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 09/19/2018] [Indexed: 11/16/2022] Open
Abstract
Taste modalities are conserved in insects and mammals. Sweet gustatory signals evoke attractive behaviors while bitter gustatory information drive aversive behaviors. Salt (NaCl) is an essential nutrient required for various physiological processes, including electrolyte homeostasis, neuronal activity, nutrient absorption, and muscle contraction. Not only mammals, even in Drosophila melanogaster, the detection of NaCl induces two different behaviors: Low concentrations of NaCl act as an attractant, whereas high concentrations act as repellant. The fruit fly is an excellent model system for studying the underlying mechanisms of salt taste due to its relatively simple neuroanatomical organization of the brain and peripheral taste system, the availability of powerful genetic tools and transgenic strains. In this review, we have revisited the literature and the information provided by various laboratories using invertebrate model system Drosophila that has helped us to understand NaCl salt taste so far. We hope that this compiled information from Drosophila will be of general significance and interest for forthcoming studies of the structure, function, and behavioral role of NaCl-sensitive (low and high concentrations) gustatory circuitry for understanding NaCl salt taste in all animals.
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Affiliation(s)
- Shivam Kaushik
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
| | - Rahul Kumar
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India.,Department of Biotechnology, Maharshi Dayanand University, Rohtak, India
| | - Pinky Kain
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
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3
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Identification of a Single Pair of Interneurons for Bitter Taste Processing in the Drosophila Brain. Curr Biol 2018; 28:847-858.e3. [PMID: 29502953 DOI: 10.1016/j.cub.2018.01.084] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 10/20/2017] [Accepted: 01/30/2018] [Indexed: 11/23/2022]
Abstract
Drosophila has become an excellent model system for investigating the organization and function of the gustatory system due to the relatively simple neuroanatomical organization of its brain and the availability of powerful genetic and transgenic technology. Thus, at the molecular and cellular levels, a great deal of insight into the peripheral detection and coding of gustatory information has already been attained. In contrast, much less is known about the central neural circuits that process this information and induce behaviorally appropriate motor output. Here, we combine functional behavioral tests with targeted transgene expression through specific driver lines to identify a single bilaterally homologous pair of bitter-sensitive interneurons that are located in the subesophageal zone of the brain. Anatomical and functional data indicate that these interneurons receive specific synaptic input from bitter-sensitive gustatory receptor neurons. Targeted transgenic activation and inactivation experiments show that these bitter-sensitive interneurons can largely suppress the proboscis extension reflex to appetitive stimuli, such as sugar and water. These functional experiments, together with calcium-imaging studies and calcium-modulated photoactivatable ratiometric integrator (CaMPARI) labeling, indicate that these first-order local interneurons play an important role in the inhibition of the proboscis extension reflex that occurs in response to bitter tastants. Taken together, our studies present a cellular identification and functional characterization of a key gustatory interneuron in the bitter-sensitive gustatory circuitry of the adult fly.
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Abstract
The ability to identify nutrient-rich food and avoid toxic substances is essential for an animal's survival. Although olfaction and vision contribute to food detection, the gustatory system acts as a final checkpoint control for food acceptance or rejection. The vinegar fly Drosophila melanogaster tastes many of the same stimuli as mammals and provides an excellent model system for comparative studies of taste detection. The relative simplicity of the fly brain and behaviors, along with the molecular genetic and functional approaches available in this system, allow the examination of gustatory neural circuits from sensory input to motor output. This review discusses the molecules and cells that detect taste compounds in the periphery and the circuits that process taste information in the brain. These studies are providing insight into how the detection of taste compounds regulates feeding decisions.
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Affiliation(s)
- Kristin Scott
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720;
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5
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Kendroud S, Bohra AA, Kuert PA, Nguyen B, Guillermin O, Sprecher SG, Reichert H, VijayRaghavan K, Hartenstein V. Structure and development of the subesophageal zone of the Drosophila brain. II. Sensory compartments. J Comp Neurol 2018; 526:33-58. [PMID: 28875566 PMCID: PMC5971197 DOI: 10.1002/cne.24316] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 07/15/2017] [Accepted: 08/15/2017] [Indexed: 12/29/2022]
Abstract
The subesophageal zone (SEZ) of the Drosophila brain processes mechanosensory and gustatory sensory input from sensilla located on the head, mouth cavity and trunk. Motor output from the SEZ directly controls the movements involved in feeding behavior. In an accompanying paper (Hartenstein et al., ), we analyzed the systems of fiber tracts and secondary lineages to establish reliable criteria for defining boundaries between the four neuromeres of the SEZ, as well as discrete longitudinal neuropil domains within each SEZ neuromere. Here we use this anatomical framework to systematically map the sensory projections entering the SEZ throughout development. Our findings show continuity between larval and adult sensory neuropils. Gustatory axons from internal and external taste sensilla of the larva and adult form two closely related sensory projections, (a) the anterior central sensory center located deep in the ventromedial neuropil of the tritocerebrum and mandibular neuromere, and (b) the anterior ventral sensory center (AVSC), occupying a superficial layer within the ventromedial tritocerebrum. Additional, presumed mechanosensory terminal axons entering via the labial nerve define the ventromedial sensory center (VMSC) in the maxilla and labium. Mechanosensory afferents of the massive array of chordotonal organs (Johnston's organ) of the adult antenna project into the centrolateral neuropil column of the anterior SEZ, creating the antenno-mechanosensory and motor center (AMMC). Dendritic projections of dye back-filled motor neurons extend throughout a ventral layer of the SEZ, overlapping widely with the AVSC and VMSC. Our findings elucidate fundamental structural aspects of the developing sensory systems in Drosophila.
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Affiliation(s)
- Sarah Kendroud
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Ali Asgar Bohra
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, India
| | | | - Bao Nguyen
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Oriane Guillermin
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Simon G. Sprecher
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | | | | | - Volker Hartenstein
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA 90095, USA
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6
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Schwarz O, Bohra AA, Liu X, Reichert H, VijayRaghavan K, Pielage J. Motor control of Drosophila feeding behavior. eLife 2017; 6:e19892. [PMID: 28211791 PMCID: PMC5315463 DOI: 10.7554/elife.19892] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 02/02/2017] [Indexed: 12/01/2022] Open
Abstract
The precise coordination of body parts is essential for survival and behavior of higher organisms. While progress has been made towards the identification of central mechanisms coordinating limb movement, only limited knowledge exists regarding the generation and execution of sequential motor action patterns at the level of individual motoneurons. Here we use Drosophila proboscis extension as a model system for a reaching-like behavior. We first provide a neuroanatomical description of the motoneurons and muscles contributing to proboscis motion. Using genetic targeting in combination with artificial activation and silencing assays we identify the individual motoneurons controlling the five major sequential steps of proboscis extension and retraction. Activity-manipulations during naturally evoked proboscis extension show that orchestration of serial motoneuron activation does not rely on feed-forward mechanisms. Our data support a model in which central command circuits recruit individual motoneurons to generate task-specific proboscis extension sequences.
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Affiliation(s)
- Olivia Schwarz
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Biozentrum University of Basel, Basel, Switzerland
- Division of Zoology and Neurobiology, Technical University Kaiserslautern, Kaiserslautern, Germany
| | - Ali Asgar Bohra
- National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore, India
| | - Xinyu Liu
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Biozentrum University of Basel, Basel, Switzerland
| | | | | | - Jan Pielage
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
- Biozentrum University of Basel, Basel, Switzerland
- Division of Zoology and Neurobiology, Technical University Kaiserslautern, Kaiserslautern, Germany
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Abstract
Following considerable progress on the molecular and cellular basis of taste perception in fly sensory neurons, the time is now ripe to explore how taste information, integrated with hunger and satiety, undergo a sensorimotor transformation to lead to the motor actions of feeding behavior. I examine what is known of feeding circuitry in adult flies from more than 250 years of work in larger flies and from newer work in Drosophila. I review the anatomy of the proboscis, its muscles and their functions (where known), its motor neurons, interneurons known to receive taste inputs, interneurons that diverge from taste circuitry to provide information to other circuits, interneurons from other circuits that converge on feeding circuits, proprioceptors that influence the motor control of feeding, and sites of integration of hunger and satiety on feeding circuits. In spite of the several neuron types now known, a connected pathway from taste inputs to feeding motor outputs has yet to be found. We are on the threshold of an era where these individual components will be assembled into circuits, revealing how nervous system architecture leads to the control of behavior.
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8
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Harris DT, Kallman BR, Mullaney BC, Scott K. Representations of Taste Modality in the Drosophila Brain. Neuron 2015; 86:1449-60. [PMID: 26051423 DOI: 10.1016/j.neuron.2015.05.026] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 04/04/2015] [Accepted: 05/11/2015] [Indexed: 12/28/2022]
Abstract
Gustatory receptors and peripheral taste cells have been identified in flies and mammals, revealing that sensory cells are tuned to taste modality across species. How taste modalities are processed in higher brain centers to guide feeding decisions is unresolved. Here, we developed a large-scale calcium-imaging approach coupled with cell labeling to examine how different taste modalities are processed in the fly brain. These studies reveal that sweet, bitter, and water sensory cells activate different cell populations throughout the subesophageal zone, with most cells responding to a single taste modality. Pathways for sweet and bitter tastes are segregated from sensory input to motor output, and this segregation is maintained in higher brain areas, including regions implicated in learning and neuromodulation. Our work reveals independent processing of appetitive and aversive tastes, suggesting that flies and mammals use a similar coding strategy to ensure innate responses to salient compounds.
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Affiliation(s)
- David T Harris
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Benjamin R Kallman
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Brendan C Mullaney
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Kristin Scott
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
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9
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LeDue EE, Chen YC, Jung AY, Dahanukar A, Gordon MD. Pharyngeal sense organs drive robust sugar consumption in Drosophila. Nat Commun 2015; 6:6667. [PMID: 25807033 PMCID: PMC4375776 DOI: 10.1038/ncomms7667] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 02/18/2015] [Indexed: 11/30/2022] Open
Abstract
The fly pharyngeal sense organs lie at the transition between external and internal nutrient sensing mechanisms. Here, we investigate the function of pharyngeal sweet gustatory receptor neurons (GRNs), demonstrating that they express a subset of the nine previously identified sweet receptors and respond to stimulation with a panel of sweet compounds. We show that pox-neuro (poxn) mutants lacking taste function in the legs and labial palps have intact pharyngeal sweet taste, which is both necessary and sufficient to drive preferred consumption of sweet compounds by prolonging ingestion. Moreover, flies putatively lacking all sweet taste show little preference for nutritive or non-nutritive sugars in a short-term feeding assay. Together, our data demonstrate that pharyngeal sense organs play an important role in directing sustained consumption of sweet compounds, and suggest that post-ingestive sugar sensing does not effectively drive food choice in a simple short-term feeding paradigm.
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Affiliation(s)
- Emily E LeDue
- Department of Zoology, Cell and Developmental Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Yu-Chieh Chen
- Interdepartmental Neuroscience Program, University of California, Riverside, California 92521, USA
| | - Aera Y Jung
- Department of Zoology, Cell and Developmental Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Anupama Dahanukar
- Interdepartmental Neuroscience Program, University of California, Riverside, California 92521, USA.,Department of Entomology, University of California, Riverside, California 92521, USA
| | - Michael D Gordon
- Department of Zoology, Cell and Developmental Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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10
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Kain P, Dahanukar A. Secondary taste neurons that convey sweet taste and starvation in the Drosophila brain. Neuron 2015; 85:819-32. [PMID: 25661186 DOI: 10.1016/j.neuron.2015.01.005] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/29/2014] [Accepted: 01/08/2015] [Indexed: 11/16/2022]
Abstract
The gustatory system provides vital sensory information to determine feeding and appetitive learning behaviors. Very little is known, however, about higher-order gustatory circuits in the highly tractable model for neurobiology, Drosophila melanogaster. Here we report second-order sweet gustatory projection neurons (sGPNs) in the Drosophila brain using a powerful behavioral screen. Silencing neuronal activity reduces appetitive behaviors, whereas inducible activation results in food acceptance via proboscis extensions. sGPNs show functional connectivity with Gr5a(+) sweet taste neurons and are activated upon sucrose application to the labellum. By tracing sGPN axons, we identify the antennal mechanosensory and motor center (AMMC) as an immediate higher-order processing center for sweet taste. Interestingly, starvation increases sucrose sensitivity of the sGPNs in the AMMC, suggesting that hunger modulates the responsiveness of the secondary sweet taste relay. Together, our results provide a foundation for studying gustatory processing and its modulation by the internal nutrient state.
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Affiliation(s)
- Pinky Kain
- Department of Entomology, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA
| | - Anupama Dahanukar
- Department of Entomology, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA.
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11
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Pool AH, Kvello P, Mann K, Cheung SK, Gordon MD, Wang L, Scott K. Four GABAergic interneurons impose feeding restraint in Drosophila. Neuron 2014; 83:164-77. [PMID: 24991960 DOI: 10.1016/j.neuron.2014.05.006] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2014] [Indexed: 10/25/2022]
Abstract
Feeding is dynamically regulated by the palatability of the food source and the physiological needs of the animal. How consumption is controlled by external sensory cues and internal metabolic state remains under intense investigation. Here, we identify four GABAergic interneurons in the Drosophila brain that establish a central feeding threshold which is required to inhibit consumption. Inactivation of these cells results in indiscriminate and excessive intake of all compounds, independent of taste quality or nutritional state. Conversely, acute activation of these neurons suppresses consumption of water and nutrients. The output from these neurons is required to gate activity in motor neurons that control meal initiation and consumption. Thus, our study reveals a layer of inhibitory control in feeding circuits that is required to suppress a latent state of unrestricted and nonselective consumption.
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Affiliation(s)
- Allan-Hermann Pool
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA
| | - Pal Kvello
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA
| | - Kevin Mann
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA
| | - Samantha K Cheung
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA
| | - Michael D Gordon
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA
| | - Liming Wang
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA
| | - Kristin Scott
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California, Berkeley, 16 Barker Hall, Berkeley, CA 94720, USA.
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12
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Mann K, Gordon MD, Scott K. A pair of interneurons influences the choice between feeding and locomotion in Drosophila. Neuron 2013; 79:754-65. [PMID: 23972600 DOI: 10.1016/j.neuron.2013.06.018] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/10/2013] [Indexed: 01/29/2023]
Abstract
The decision to engage in one behavior often precludes the selection of others, suggesting cross-inhibition between incompatible behaviors. For example, the likelihood to initiate feeding might be influenced by an animal's commitment to other behaviors. Here, we examine the modulation of feeding behavior in the fruit fly, Drosophila melanogaster, and identify a pair of interneurons in the ventral nerve cord that is activated by stimulation of mechanosensory neurons and inhibits feeding initiation, suggesting that these neurons suppress feeding while the fly is walking. Conversely, inhibiting activity in these neurons promotes feeding initiation and inhibits locomotion. These studies demonstrate the mutual exclusivity between locomotion and feeding initiation in the fly, isolate interneurons that influence this behavioral choice, and provide a framework for studying the neural basis for behavioral exclusivity in Drosophila.
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Affiliation(s)
- Kevin Mann
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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13
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Abstract
Rhythmic motor behaviors such as feeding are driven by neural networks that can be modulated by external stimuli and internal states. In Drosophila, ingestion is accomplished by a pump that draws fluid into the esophagus. Here we examine how pumping is regulated and characterize motor neurons innervating the pump. Frequency of pumping is not affected by sucrose concentration or hunger but is altered by fluid viscosity. Inactivating motor neurons disrupts pumping and ingestion, whereas activating them elicits arrhythmic pumping. These motor neurons respond to taste stimuli and show prolonged activity to palatable substances. This work describes an important component of the neural circuit for feeding in Drosophila and is a step toward understanding the rhythmic activity producing ingestion.
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Gordon MD, Scott K. Motor control in a Drosophila taste circuit. Neuron 2009; 61:373-84. [PMID: 19217375 DOI: 10.1016/j.neuron.2008.12.033] [Citation(s) in RCA: 375] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 12/24/2008] [Accepted: 12/29/2008] [Indexed: 10/21/2022]
Abstract
Tastes elicit innate behaviors critical for directing animals to ingest nutritious substances and reject toxic compounds, but the neural basis of these behaviors is not understood. Here, we use a neural silencing screen to identify neurons required for a simple Drosophila taste behavior and characterize a neural population that controls a specific subprogram of this behavior. By silencing and activating subsets of the defined cell population, we identify the neurons involved in the taste behavior as a pair of motor neurons located in the subesophageal ganglion (SOG). The motor neurons are activated by sugar stimulation of gustatory neurons and inhibited by bitter compounds; however, experiments utilizing split-GFP detect no direct connections between the motor neurons and primary sensory neurons, indicating that further study will be necessary to elucidate the circuitry bridging these populations. Combined, these results provide a general strategy and a valuable starting point for future taste circuit analysis.
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Affiliation(s)
- Michael D Gordon
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, 291 Life Sciences Addition, University of California, Berkeley, Berkeley, CA 94720, USA
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15
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Spiess R, Schoofs A, Heinzel HG. Anatomy of the stomatogastric nervous system associated with the foregut in Drosophila melanogaster and Calliphora vicina third instar larvae. J Morphol 2008; 269:272-82. [PMID: 17960761 DOI: 10.1002/jmor.10581] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The stomatogastric nervous system (SNS) associated with the foregut was studied in 3rd instar larvae of Drosophila melanogaster and Calliphora vicina (blowfly). In both species, the foregut comprises pharynx, esophagus, and proventriculus. Only in Calliphora does the esophagus form a crop. The position of nerves and neurons was investigated with neuronal tracers in both species and GFP expression in Drosophila. The SNS is nearly identical in both species. Neurons are located in the proventricular and the hypocerebral ganglion (HCG), which are connected to each other by the proventricular nerve. Motor neurons for pharyngeal muscles are located in the brain not, as in other insect groups, in the frontal ganglion. The position of the frontal ganglion is taken by a nerve junction devoid of neurons. The junction is composed of four nerves: the frontal connectives that fuse with the antennal nerves (ANs), the frontal nerve innervating the cibarial dilator muscles and the recurrent nerve that innervates the esophagus and projects to the HCG. Differences in the SNS are restricted to a crop nerve only present in Calliphora and an esophageal ganglion that only exists in Drosophila. The ganglia of the dorsal organs give rise to the ANs, which project to the brain. The extensive conformity of the SNS of both species suggests functional parallels. Future electrophysiological studies of the motor circuits in the SNS of Drosophila will profit from parallel studies of the homologous but more accessible structures in Calliphora.
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Affiliation(s)
- Roland Spiess
- Department of Neurobiology, Institute for Zoology, University of Bonn, Poppelsdorfer Schloss, 53115 Bonn, Germany.
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16
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Abstract
The chemical senses-smell and taste-allow animals to evaluate and distinguish valuable food resources from dangerous substances in the environment. The central mechanisms by which the brain recognizes and discriminates attractive and repulsive odorants and tastants, and makes behavioral decisions accordingly, are not well understood in any organism. Recent molecular and neuroanatomical advances in Drosophila have produced a nearly complete picture of the peripheral neuroanatomy and function of smell and taste in this insect. Neurophysiological experiments have begun to provide insight into the mechanisms by which these animals process chemosensory cues. Given the considerable anatomical and functional homology in smell and taste pathways in all higher animals, experimental approaches in Drosophila will likely provide broad insights into the problem of sensory coding. Here we provide a critical review of the recent literature in this field and comment on likely future directions.
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Affiliation(s)
- Leslie B Vosshall
- Laboratory of Neurogenetics and Behavior, The Rockefeller University, New York, NY 10021-6399, USA.
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17
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Schoofs A, Spiess R. Anatomical and functional characterisation of the stomatogastric nervous system of blowfly (Calliphora vicina) larvae. JOURNAL OF INSECT PHYSIOLOGY 2007; 53:349-60. [PMID: 17306827 DOI: 10.1016/j.jinsphys.2006.12.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Revised: 12/20/2006] [Accepted: 12/21/2006] [Indexed: 05/14/2023]
Abstract
The anatomy and functionality of the stomatogastric nervous system (SNS) of third-instar larvae of Calliphora vicina was characterised. As in other insects, the Calliphora SNS consists of several peripheral ganglia involved in foregut movement regulation. The frontal ganglion gives rise to the frontal nerve and is connected to the brain via the frontal connectives and antennal nerves (ANs). The recurrent nerve connects the frontal- to the hypocerebral ganglion from which the proventricular nerve runs to the proventricular ganglion. Foregut movements include rhythmic contractions of the cibarial dilator muscles (CDM), wavelike movements of crop and oesophagus and contractions of the proventriculus. Transections of SNS nerves indicate mostly myogenic crop and oesophagus movements and suggest modulatory function of the associated nerves. Neural activity in the ANs, correlating with postsynaptic potentials on the CDM, demonstrates a motor pathway from the brain to CDM. Crop volume is monitored by putative stretch receptors. The respective sensory pathway includes the recurrent nerve and the proventricular nerve. The dorsal organs (DOs) are directly connected to the SNS. Mechanical stimulation of the DOs evokes sensory activity in the AN. This suggests the DOs can provide sensory input for temporal coordination of feeding behaviour.
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Affiliation(s)
- Andreas Schoofs
- Institut für Zoologie, Abteilung Neurobiologie, Universität Bonn, Poppelsdorfer Schloss, 53115 Bonn, Germany
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Josens R, Falibene A, Gontijo ADF. Electrical signals during nectar sucking in the carpenter ant Camponotus mus. JOURNAL OF INSECT PHYSIOLOGY 2006; 52:1234-42. [PMID: 17069844 DOI: 10.1016/j.jinsphys.2006.09.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Revised: 09/07/2006] [Accepted: 09/11/2006] [Indexed: 05/12/2023]
Abstract
Ants of the same size can vary their intake rate of a given sucrose solution depending on the colony's needs for carbohydrates. As this capacity has not yet been described for another insect, the question of how they can do that was the focus of our work. When viscosity and ant-morphometry remain constant, changes in intake rate can only be attributed to the sucking forces. The aim of this study was to analyze the nectar sucking activity in the ant Camponotus mus. Feeding behavior seems to be under motivational control; therefore, we developed a non-invasive experimental device. We recorded the electrical signal generated during nectar feeding by offering ants sucrose solutions of different concentrations (from 10%w/w to 70%w/w). The signal frequency was between 2 and 12 peaks/s. We could distinguish two different patterns of electrical signal during feeding depending on the solution concentration. Only the more concentrated solutions reached frequencies higher than 7 peaks/s and the signal performance was quite irregular. For the other concentrations (10%, 30% and 50%), signal frequencies were lower than 6 peaks/s and the signal pattern was sinusoidal, regular and decreased with intake in all cases. We discuss the possible implications of these two signal patterns.
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Affiliation(s)
- Roxana Josens
- Departamento de Biodiversidady Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria (C1428 EHA), Buenos Aires, Argentina.
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Jørgensen K, Kvello P, Almaas TJ, Mustaparta H. Two closely located areas in the suboesophageal ganglion and the tritocerebrum receive projections of gustatory receptor neurons located on the antennae and the proboscis in the moth Heliothis virescens. J Comp Neurol 2006; 496:121-34. [PMID: 16528726 DOI: 10.1002/cne.20908] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sucrose stimulation of gustatory receptor neurons on the antennae, the tarsi, and the mouthparts elicits the proboscis extension reflex in many insect species, including lepidopterans. The sensory pathways involved in this reflex have only partly been investigated, and in hymenopterans only. The present paper concerns the pathways of the gustatory receptor neurons on the antennae and on the proboscis involved in the proboscis extension reflex in the moth Heliothis virescens (Lepidoptera; Noctuidae). Fluorescent dyes were applied to the contact chemosensilla, sensilla chaetica on the antennae, and sensilla styloconica on the proboscis, permitting tracing of the axons of the gustatory receptor neurons in the central nervous system. The stained axons showed projections from the two appendages in two closely located but distinct areas in the suboesophageal ganglion (SOG)/tritocerebrum. The projections of the antennal gustatory receptor neurons were located posterior-laterally to those from the proboscis. Electrophysiological recordings from the receptor neurons in s. chaetica during mechanical and chemical stimulation were performed, showing responses of one mechanosensory and of several gustatory receptor neurons. Separate neurons showed excitatory responses to sucrose and sinigrin. The effect of these two tastants on the proboscis extension reflex was tested by repeated stimulations with solutions of the two compounds. Whereas sucrose elicited extension in 100% of the individuals in all repetitions, sinigrin elicited extension in fewer individuals, a number that decreased with repeated stimulation.
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Affiliation(s)
- Kari Jørgensen
- Neuroscience Unit, Department of Biology, Norwegian University of Science and Technology, N-7489 Trondheim, Norway
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Kvello P, Almaas TJ, Mustaparta H. A confined taste area in a lepidopteran brain. ARTHROPOD STRUCTURE & DEVELOPMENT 2006; 35:35-45. [PMID: 18089056 DOI: 10.1016/j.asd.2005.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2005] [Accepted: 10/20/2005] [Indexed: 05/25/2023]
Abstract
Knowledge about the neuronal pathways of the taste system is interesting both for studying taste coding and appetitive learning of odours. We here present the morphology of the sensilla styloconica on the proboscis of the moth Heliothis virescens and the projections of the associated receptor neurones in the central nervous system. The morphology of the sensilla was studied by light microscopy and by scanning- and transmission electron microscopy. Each sensillum contains three or four sensory neurones; one mechanosensory and two or three chemosensory. The receptor neurones were stained with neurobiotin tracer combined with avidin-fluorescein conjugate, and the projections were viewed in a confocal laser-scanning microscope. The stained axons entered the suboesophageal ganglion via the maxillary nerves and were divided into two categories based on their projection pattern. Category one projected exclusively ipsilaterally in the dorsal suboesophageal ganglion/tritocerebrum and category two projected bilaterally and more ventrally in the suboesophageal ganglion confined to the anterior surface of the neuropil. The bilateral projecting neurones had one additional branch terminating ipsilaterally in the dorsal suboesophageal ganglion/tritocerebrum. A possible segregation of the two categories of projections as taste and mechanosensory is discussed.
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Affiliation(s)
- Pål Kvello
- Department of Biology, Norwegian University of Science and Technology, Neuroscience Unit, MTFS, NO 7489 Trondheim, Norway
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Ramaekers A, Parmentier ML, Lasnier C, Bockaert J, Grau Y. Distribution of metabotropic glutamate receptor DmGlu-A in Drosophila melanogaster central nervous system. J Comp Neurol 2001; 438:213-25. [PMID: 11536189 DOI: 10.1002/cne.1310] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
L-glutamate is the excitatory neurotransmitter at neuromuscular junctions in insects. It may also be involved in neurotransmission within the central nervous system (CNS), but its function therein remains elusive. The roles of glutamatergic synapses in the Drosophila melanogaster CNS were investigated, with focus on the study of DmGluRA, a G-protein-coupled glutamate receptor. In a first attempt to determine the function of this receptor, we describe its distribution in the larval and adult Drosophila CNS, using a polyclonal antibody raised against the C-terminal sequence of the protein. DmGluRA is expressed in a reproducible pattern both in the larva and in the adult. In particular, DmGluRA can be found in the antennal lobes, the optic lobes, the central complex, and the median bundle in the adult CNS. However, DmGluRA-containing neurons represented only a small fraction of all CNS neurons. DmGluRA immunoreactivity was not detected at the larval neuromuscular junction nor in the body wall muscles. The correlations between DmGluRA distribution and previously described glutamate-like immunoreactivity patterns, as well as the implications of these observations concerning the possible functions of DmGluRA in the Drosophila CNS, are discussed.
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Affiliation(s)
- A Ramaekers
- UPR CNRS 9023, Mécanismes Moléculaires des Communications Cellulaires, CCIPE, 34094 Montpellier Cedex 5, France
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Abstract
Insects have been favorites for the study of taste perception in the last few decades. They have been used for anatomical, behavioral, developmental, genetic, and physiological studies related to gustation and feeding response. Several genes known to affect the formation of gustatory sensilla or alter the feeding behavior of insects such as Drosophila are known. Studies related to signal transduction, coding of gustatory information, and the nature and constitution of genes involved in taste perception have also been taken up with insects in recent years. The understanding of basic mechanisms of taste perception in insects is likely to lead to better management of useful as well as harmful insects.
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Affiliation(s)
- R N Singh
- Anatomy and Electron Microscopy Laboratory, Tata Institute of Fundamental Research, Bombay, India.
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Rajashekhar KP, Singh RN. Neuroarchitecture of the tritocerebrum of Drosophila melanogaster. J Comp Neurol 1994; 349:633-45. [PMID: 7860793 DOI: 10.1002/cne.903490410] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The organisation of the tritocerebrum of Drosophila melanogaster was studied by Bodian-Protargol reduced silver staining, Golgi-silver impregnation, horseradish peroxidase (HRP), and cobalt-chloride labelling of neurones and transmission electron microscopy. Nerve fibres of six categories were found to project to the tritocerebrum. (1 and 2) The sensory fibres from the internal mouthpart sensilla known to course along pharyngeal and accessory pharyngeal nerves were found to project in mainly two tiers, in the tritocerebrum. (3) Stomodaeal nerve fibres also project along the pharyngeal nerve, to the tritocerebrum. (4) Cells of the pars intercerebralis (PI) project along the median bundle and arborise in the tritocerebrum. HRP labelling and subsequent examination by transmission electron microscopy indicated their neurosecretory nature. (5 and 6) Two tracts of ascending fibres, designated as dorsal and ventral ascending tracts, were found to project to the tritocerebrum. Some of the sensory fibres from the labial nerve extend close to the sensory projections of the tritocerebrum, suggesting a possible convergence of the two sensory inputs. In the tritocerebrum, the sensory input, the stomodaeal input, the neurosecretory fibres of PI, and the ascending fibres were found to have overlapping fields, suggesting mutual interaction. The medial subesophageal ganglion and the tritocerebrum may interact through the ventral ascending tract.
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Affiliation(s)
- K P Rajashekhar
- Molecular Biology Unit, Tata Institute of Fundamental Research, Colaba, Bombay, India
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