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Drosophila tracks carbon dioxide in flight.

ABSTRACT: Carbon dioxide (CO(2)) elicits an attractive host-seeking response from mosquitos yet is innately aversive to Drosophila melanogaster despite being a plentiful byproduct of attractive fermenting food sources. Prior studies used walking flies exclusively, yet adults track distant food sources on the wing. Here we show that a fly tethered within a magnetic field allowing free rotation about the yaw axis actively seeks a narrow CO(2) plume during flight. Genetic disruption of the canonical CO(2)-sensing olfactory neurons does not alter in-flight attraction to CO(2); however, antennal ablation and genetic disruption of the Ir64a acid sensor do. Surprisingly, mutation of the obligate olfactory coreceptor (Orco) does not abolish CO(2) aversion during walking yet eliminates CO(2) tracking in flight. The biogenic amine octopamine regulates critical physiological processes during flight, and blocking synaptic output from octopamine neurons inverts the valence assigned to CO(2) and elicits an aversive response in flight. Combined, our results suggest that a novel Orco-mediated olfactory pathway that gains sensitivity to CO(2) in flight via changes in octopamine levels, along with Ir64a, quickly switches the valence of a key environmental stimulus in a behavioral-state-dependent manner.

SUBMITTER: Wasserman S

PROVIDER: S-EPMC3810385 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Drosophila tracks carbon dioxide in flight.

Wasserman Sara S Salomon Alexandra A Frye Mark A MA

Current biology : CB 20130124 4

Carbon dioxide (CO(2)) elicits an attractive host-seeking response from mosquitos yet is innately aversive to Drosophila melanogaster despite being a plentiful byproduct of attractive fermenting food sources. Prior studies used walking flies exclusively, yet adults track distant food sources on the wing. Here we show that a fly tethered within a magnetic field allowing free rotation about the yaw axis actively seeks a narrow CO(2) plume during flight. Genetic disruption of the canonical CO(2)-se ...[more]

PMID: 23352695

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Project description:Mechanical ventilation (MV) represents a lifesaving treatment for patients with respiratory failure, but it could be harmful through the development of ventilator-induced lung injury (VILI). In patients with acute respiratory distress syndrome (ARDS), protective MV strategies with low tidal volume to minimize VILI have been demonstrated to reduce lung injury and mortality. However, they can be limited by the emergence of uncontrolled hypercapnia. Similarly, in COPD patients, noninvasive MV failure often is associated with a progressive rise in arterial CO2 and need for endotracheal intubation, with higher risk of hospital mortality. Minimally invasive extracorporeal CO2 removal systems (ECCO2R) theoretically can remove the entire amount of the CO2 produced in the body per minute. In ARDS patients, ECCO2R may further reduce the risk of VILI ensuring ultraprotective MV and avoiding hypercapnia. In patients with exacerbation of COPD, ECCO2R may help to avoid intubation or facilitate weaning from invasive MV. In intensive care unit, concomitant renal and respiratory failure with MV is one of the strongest risk factors for hospital mortality. Combining ECCO2R and renal replacement therapy may support respiratory and renal functions and limit the side effects of MV. However, the need for systemic anticoagulation and the related risk of bleeding still represent a concern for a wider application of ECCO2R devices. In conclusion, ECCO2R is an effective support therapy to MV to limit its invasiveness and side effects, but its efficacy and safety must be proven in well-designed clinical trials. Objectives This chapter will:1 Explain the physiology of CO2 removal during extracorporeal support.2 Describe potential clinical applications of extracorporeal CO2 removal systems (ECCO2R) support therapy in patients with acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD) as well as in those with acute kidney injury requiring renal replacement therapy.

Project description:Behavioural responses of animals to volatiles in their environment are generally dependent on context. Most natural odours are mixtures of components that can each induce different behaviours when presented on their own. We have investigated how a complex of two olfactory stimuli is evaluated by Drosophila flies in a free-flying two-trap choice assay and how these stimuli are encoded in olfactory receptor neurons. We first observed that volatiles from apple cider vinegar attracted flies while carbon dioxide (CO2) was avoided, confirming their inherent positive and negative values. In contradiction with previous results obtained from walking flies in a four-field olfactometer, in the present assay the addition of CO2 to vinegar increased rather than decreased the attractiveness of vinegar. This effect was female-specific even though males and females responded similarly to CO2 and vinegar on their own. To test whether the female-specific behavioural response to the mixture correlated with a sexual dimorphism at the peripheral level we recorded from olfactory receptor neurons stimulated with vinegar, CO2 and their combination. Responses to vinegar were obtained from three neuron classes, two of them housed with the CO2-responsive neuron in ab1 sensilla. Sensitivity of these neurons to both CO2 and vinegar per se did not differ between males and females and responses from female neurons did not change when CO2 and vinegar were presented simultaneously. We also found that CO2-sensitive neurons are particularly well adapted to respond rapidly to small concentration changes irrespective of background CO2 levels. The ability to encode temporal properties of stimulations differs considerably between CO2- and vinegar-sensitive neurons. These properties may have important implications for in-flight navigation when rapid responses to fragmented odour plumes are crucial to locate odour sources. However, the flies' sex-specific response to the CO2-vinegar combination and the context-dependent hedonics most likely originate from central rather than peripheral processing.

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Drosophila tracks carbon dioxide in flight.

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Drosophila tracks carbon dioxide in flight.

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