Name: combining quantitative food-intake assays and forcibly activating neurons to study appetite in drosophila
Uploaded: 2018-04-24T12:30:00
Description: Watch this Scientific Journal Video about Combining Quantitative Food-intake Assays and Forcibly Activating Neurons to Study Appetite in Drosophila at JoVE.com

This work was supported in part by National Basic Research Program of China (2012CB825504), National Natural Science Foundation of China (91232720 and 9163210042), Chinese Academy of Sciences (CAS) (GJHZ201302 and QYZDY-SSW-SMC015), Bill and Melinda Gates Foundation (OPP1119434), and 100-Talents Program of CAS to Y. Zhu.

1. Preparing the feeding chamber
Note: The feeding chamber for dye-labeling feeding assay consists of two parts: the outside container (as a cover) and the inside container (as food source).
<ol>
	<li>Modify the outside container from a glass vial for culturing Drosophila (with an internal diameter of 31.8 mm and a height of 80 mm) (Figure 1A, 1C). Cover the bottom of the container with a layer of 1% agarose (5 mL) to k...

<ol>
	<li>Gao, Q., Horvath, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurobiology+of+feeding+and+energy+expenditure.">Neurobiology of feeding and energy expenditure.</a> Annu Rev Neurosci. 30, 367-398 (2007).</li><li>Bjordal, M., Arquier, N., Kniazeff, J., Pin, J. P., Leopold, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensing+of+amino+acids+in+a+dopaminergic+circuitry+promotes+rejection+of+an+incomplete+diet+in+Drosophila.">Sensing of amino acids in a dopaminergic circuitry promotes rejection of an incomplete diet in Drosophila.</a> Cell. 156 (3), 510-521 (2014).</li><li>Edgecomb, R. S., Harth, C. E., Schneiderman, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+feeding+behavior+in+adult+Drosophila+melanogaster+varies+with+feeding+regime+and+nutritional+state.">Regulation of feeding behavior in adult Drosophila melanogaster varies with feeding regime and nutritional state.</a> J Exp Biol. 197, 215-235 (1994).</li><li>Miyamoto, T., Slone, J., Song, X., Amrein, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+fructose+receptor+functions+as+a+nutrient+sensor+in+the+Drosophila+brain.">A fructose receptor functions as a nutrient sensor in the Drosophila brain.</a> Cell. 151 (5), 1113-1125 (2012).</li><li>Morton, G. J., Cummings, D. E., Baskin, D. G., Barsh, G. S., Schwartz, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Central+nervous+system+control+of+food+intake+and+body+weight.">Central nervous system control of food intake and body weight.</a> Nature. 443 (7109), 289-295 (2006).</li><li>Pool, A. H., Scott, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Feeding+regulation+in+Drosophila.">Feeding regulation in Drosophila.</a> Curr Opin Neurobiol. 29, 57-63 (2014).</li><li>Soderberg, J. A., Carlsson, M. A., Nassel, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insulin-Producing+Cells+in+the+Drosophila+Brain+also+Express+Satiety-Inducing+Cholecystokinin-Like+Peptide,+Drosulfakinin.">Insulin-Producing Cells in the Drosophila Brain also Express Satiety-Inducing Cholecystokinin-Like Peptide, Drosulfakinin.</a> Front Endocrinol (Lausanne). 3, 109 (2012).</li><li>Stafford, J. W., Lynd, K. M., Jung, A. Y., Gordon, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integration+of+taste+and+calorie+sensing+in+Drosophila.">Integration of taste and calorie sensing in Drosophila.</a> J Neurosci. 32 (42), 14767-14774 (2012).</li><li>Wu, Q., Zhang, Y., Xu, J., Shen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+hunger-driven+behaviors+by+neural+ribosomal+S6+kinase+in+Drosophila.">Regulation of hunger-driven behaviors by neural ribosomal S6 kinase in Drosophila.</a> Proc Natl Acad Sci U S A. 102 (37), 13289-13294 (2005).</li><li>Itskov, P. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+monitoring+and+quantitative+analysis+of+feeding+behaviour+in+Drosophila.">Automated monitoring and quantitative analysis of feeding behaviour in Drosophila.</a> Nat Commun. 5, 4560 (2014).</li><li>Mair, W., Piper, M. D., Partridge, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calories+do+not+explain+extension+of+life+span+by+dietary+restriction+in+Drosophila.">Calories do not explain extension of life span by dietary restriction in Drosophila.</a> PLoS Biol. 3 (7), e223 (2005).</li><li>Diegelmann, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+CApillary+FEeder+Assay+Measures+Food+Intake+in+Drosophila+melanogaster.">The CApillary FEeder Assay Measures Food Intake in Drosophila melanogaster.</a> J Vis Exp. (121), (2017).</li><li>Ja, W. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prandiology+of+Drosophila+and+the+CAFE+assay.">Prandiology of Drosophila and the CAFE assay.</a> Proc Natl Acad Sci U S A. 104 (20), 8253-8256 (2007).</li><li>Shiraiwa, T., Carlson, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proboscis+extension+response+(PER)+assay+in+Drosophila.">Proboscis extension response (PER) assay in Drosophila.</a> J Vis Exp. (3), e193 (2007).</li><li>Qi, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+quantitative+feeding+assay+in+adult+Drosophila+reveals+rapid+modulation+of+food+ingestion+by+its+nutritional+value.">A quantitative feeding assay in adult Drosophila reveals rapid modulation of food ingestion by its nutritional value.</a> Mol Brain. 8, 87 (2015).</li><li>Ja, W. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Water-+and+nutrient-dependent+effects+of+dietary+restriction+on+Drosophila+lifespan.">Water- and nutrient-dependent effects of dietary restriction on Drosophila lifespan.</a> Proc Natl Acad Sci U S A. 106 (44), 18633-18637 (2009).</li><li>Deshpande, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+Drosophila+food+intake:+comparative+analysis+of+current+methodology.">Quantifying Drosophila food intake: comparative analysis of current methodology.</a> Nat Methods. 11 (5), 535-540 (2014).</li><li>Deshpande, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acidic+Food+pH+Increases+Palatability+and+Consumption+and+Extends+Drosophila+Lifespan.">Acidic Food pH Increases Palatability and Consumption and Extends Drosophila Lifespan.</a> J Nutr. 145 (12), 2789-2796 (2015).</li><li>Dus, M., Min, S., Keene, A. C., Lee, G. Y., Suh, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Taste-independent+detection+of+the+caloric+content+of+sugar+in+Drosophila.">Taste-independent detection of the caloric content of sugar in Drosophila.</a> Proc Natl Acad Sci U S A. 108 (28), 11644-11649 (2011).</li><li>Shen, P., Cai, H. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+neuropeptide+F+mediates+integration+of+chemosensory+stimulation+and+conditioning+of+the+nervous+system+by+food.">Drosophila neuropeptide F mediates integration of chemosensory stimulation and conditioning of the nervous system by food.</a> J Neurobiol. 47 (1), 16-25 (2001).</li><li>Yang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Octopamine+mediates+starvation-induced+hyperactivity+in+adult+Drosophila.">Octopamine mediates starvation-induced hyperactivity in adult Drosophila.</a> Proc Natl Acad Sci U S A. 112 (16), 5219-5224 (2015).</li><li>Ramdya, P., Schneider, J., Levine, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+neurogenetics+of+group+behavior+in+Drosophila+melanogaster.">The neurogenetics of group behavior in Drosophila melanogaster.</a> J Exp Biol. 220 (Pt 1), 35-41 (2017).</li><li>Sanchez-Alcaniz, J. A., Zappia, G., Marion-Poll, F., Benton, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+mechanosensory+receptor+required+for+food+texture+detection+in+Drosophila.">A mechanosensory receptor required for food texture detection in Drosophila.</a> Nat Commun. 8, 14192 (2017).</li><li>Zhan, Y. P., Liu, L., Zhu, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Taotie+neurons+regulate+appetite+in+Drosophila.">Taotie neurons regulate appetite in Drosophila.</a> Nat Commun. 7, 13633 (2016).</li><li>Yu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+starvation-induced+hyperactivity+by+insulin+and+glucagon+signaling+in+adult+Drosophila.">Regulation of starvation-induced hyperactivity by insulin and glucagon signaling in adult Drosophila.</a> Elife. 5, (2016).</li><li>Wood, J. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sirtuin+activators+mimic+caloric+restriction+and+delay+ageing+in+metazoans.">Sirtuin activators mimic caloric restriction and delay ageing in metazoans.</a> Nature. 430 (7000), 686-689 (2004).</li><li>Inagaki, H. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualizing+Neuromodulation+In+Vivo:+TANGO-Mapping+of+Dopamine+Signaling+Reveals+Appetite+Control+of+Sugar+Sensing.">Visualizing Neuromodulation In Vivo: TANGO-Mapping of Dopamine Signaling Reveals Appetite Control of Sugar Sensing.</a> Cell. 148 (3), 583-595 (2012).</li><li>Wong, R., Piper, M. D., Wertheim, B., Partridge, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+food+intake+in+Drosophila.">Quantification of food intake in Drosophila.</a> PLoS One. 4 (6), e6063 (2009).</li><li>Sen, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Moonwalker+Descending+Neurons+Mediate+Visually+Evoked+Retreat+in+Drosophila.">Moonwalker Descending Neurons Mediate Visually Evoked Retreat in Drosophila.</a> Curr Biol. 27 (5), 766-771 (2017).</li><li>Ewing, L. S., Ewing, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Courtship+of+Drosophila+melanogaster+in+large+observation+chambers:+the+influence+of+female+reproductive+state.">Courtship of Drosophila melanogaster in large observation chambers: the influence of female reproductive state.</a> Behaviour. 101 (1), 243-252 (1987).</li><li>Chatterjee, A., Tanoue, S., Houl, J. H., Hardin, P. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+gustatory+physiology+and+appetitive+behavior+by+the+Drosophila+circadian+clock.">Regulation of gustatory physiology and appetitive behavior by the Drosophila circadian clock.</a> Curr Biol. 20 (4), 300-309 (2010).</li><li>Xu, K., Zheng, X., Sehgal, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+feeding+and+metabolism+by+neuronal+and+peripheral+clocks+in+Drosophila.">Regulation of feeding and metabolism by neuronal and peripheral clocks in Drosophila.</a> Cell Metab. 8 (4), 289-300 (2008).</li><li>Hamada, F. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+internal+thermal+sensor+controlling+temperature+preference+in+Drosophila.">An internal thermal sensor controlling temperature preference in Drosophila.</a> Nature. 454 (7201), 217-255 (2008).</li><li>Viswanath, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ion+channels+-+Opposite+thermosensor+in+fruitfly+and+mouse.">Ion channels - Opposite thermosensor in fruitfly and mouse.</a> Nature. 423 (6942), 822-823 (2003).</li><li>Yu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+starvation-induced+hyperactivity+by+insulin+and+glucagon+signaling+in+adult+Drosophila.">Regulation of starvation-induced hyperactivity by insulin and glucagon signaling in adult Drosophila.</a> Elife. 5, (2016).</li><li>Klapoetke, N. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Independent+optical+excitation+of+distinct+neural+populations.">Independent optical excitation of distinct neural populations.</a> Nat Methods. 11 (3), 338-346 (2014).</li><li>Viswanath, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Opposite+thermosensor+in+fruitfly+and+mouse.">Opposite thermosensor in fruitfly and mouse.</a> Nature. 423 (6942), 822-823 (2003).</li><li>Brand, A. H., Perrimon, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+Gene-Expression+as+a+Means+of+Altering+Cell+Fates+and+Generating+Dominant+Phenotypes.">Targeted Gene-Expression as a Means of Altering Cell Fates and Generating Dominant Phenotypes.</a> Development. 118 (2), 401-415 (1993).</li><li>Lee, K. S., You, K. H., Choo, J. K., Han, Y. M., Yu, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+short+neuropeptide+F+regulates+food+intake+and+body+size.">Drosophila short neuropeptide F regulates food intake and body size.</a> J Biol Chem. 279 (49), 50781-50789 (2004).</li><li>Marella, S., Mann, K., Scott, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dopaminergic+Modulation+of+Sucrose+Acceptance+Behavior+in+Drosophila.">Dopaminergic Modulation of Sucrose Acceptance Behavior in Drosophila.</a> Neuron. 73 (5), 941-950 (2012).</li><li>Albin, S. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Subset+of+Serotonergic+Neurons+Evokes+Hunger+in+Adult+Drosophila.">A Subset of Serotonergic Neurons Evokes Hunger in Adult Drosophila.</a> Current Biology. 25 (18), 2435-2440 (2015).</li><li>Ro, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Serotonin+signaling+mediates+protein+valuation+and+aging.">Serotonin signaling mediates protein valuation and aging.</a> eLife. 5, e16843 (2016).</li></ol>

This report focuses on the technical process of dye-labeling feeding assays of food consumption in the context of thermogenetic and optogenetic activation to manipulate neurons controlling feeding. This simple and reliable protocol will help to elucidate the function of candidate neurons in feeding control, to measure the food preference of flies, and to identify novel players in the feeding control circuits via feeding-based genetic screens24.
The dye labeling strategy...

Quantifying the amount of food ingested is important for evaluating multiple aspects of feeding controls by the brain in responding to the internal needs (such as hunger states) and external factors (such as food quality and palatability)1,2,3,4,5,6,7,8,9. In recent years, the efforts of deciphering the neural substrates of feeding control in Drosophila lead to the development of multiple assays to directly quantify the amount of food ingested or serve as an indicator of feeding motivation10,11,12,13,14,15,16.
The CApillary FEeder (CAFE) assay12,13 was developed to measure the amount of consumption of liquid food in a glass microcapillary. The CAFE assay is highly sensitive and reproducible17 and simplifies the measurement of food consumption, especially for quantifying long-term feeding18. However, this assay requires the flies to climb to the tip of the microcapillary and feed upside-down, which is not suitable for all strains. Additionally, because the flies to be tested using the CAFE assay have to be reared on liquid food, the effect of these rearing conditions on metabolism status or the potential malnutrition remains to be determined.
The Proboscis Extension Response (PER) assay11,14 counts the frequency of proboscis extension responses toward gentle touches of food drops. PER assay proved as an excellent way to evaluate feeding motivation of individual fly and asses the influence of palatability and content of food18,19. However, it is not a direct quantification of intake amount.
Recently, a semi-automatic method, the manual feeding assay (MAFE)15, was developed. In MAFE, a single immobilized fly is fed manually with a microcapillary containing food. Given that proboscis extension responses and food consumption can be monitored simultaneously, MAFE is suitable for assessing nutrient values and the effects of pharmacological manipulation. However, immobilizing a fly might negatively impact its behavioral performance, including feeding.
Additionally, fly Proboscis and Activity Detector (FlyPAD)10 was developed to automatically quantify feeding behavior. Using machine vision methods, FlyPAD records physical interactions between a fly and food to quantify the frequency and duration of proboscis extensions as an indicator of feeding motivation. FlyPAD provides a high-throughput approach to monitor the feeding behaviors of a free-moving fly, although the sensitivity and robustness of this system remains to be further confirmed by more studies12.
Labeling strategies are frequently used to estimate food ingestion in flies. It is common to label food with chemical tracers and, after feeding, measure the amount of ingested tracer to calculate the quantity of food intake. Radioactive tracers16,17,20,21,22,23,24,25 allow for the detection through the cuticle without homogenization of the flies. This method provides remarkably low variability and high sensitivity18, and is feasible for long-term study of food intake. However, the availability of usable radioisotopes and different rates of absorbance and excretion should be taken into consideration when working with this assay.
Labeling and tracing food intake with non-toxic food colors is a safer and simpler alternative2,3,26,27,28. Flies are homogenized after feeding with food containing soluble and non-absorbable dyes, and the amount of the ingested dye is later quantified using a spectrophotometer3,24,28,29. The labeling strategy is easy to perform and provides high efficiency, but with a caveat. The volume of food intake estimated from the ingested dye is smaller than the actual volume because excretion begins as early as 15 min after flies start feeding17. Additionally, the assay assesses food ingestion typically within a 60-min period, which is only suitable for investigation of short-term feeding behavior24,28. Moreover, multiple internal and external factors, such as genotype17, gender17, mated state17, rearing density30, circadian rhythm31,32, and food quality3,8,16, influence food intake. Therefore, the feeding duration might need to be adjusted according to specific experimental conditions. Besides facilitating the quantification of food intake, food colors are also used to assess food choices2,19,27, and to visualize the meniscus in a microcapillary in CAFE assay12.
Here, we introduce a protocol combined manipulation of neuronal activity with dye-labeling approach. This strategy has been proved useful in our neurogenetic study on feeding control in adult fruit flies24. The visual scoring method allows for a quick estimation of food consumption; thus, it is useful for screening through a large number of strains in a timely fashion. The candidates from the screen are then analyzed in detail using a colorimetric method to provide objective and precise quantification in additional study.
Besides the feeding assays, we also describe the thermogenetic27,33,34,35 and optogenetic36 methods of forcibly activating target neurons in Drosophila. To activate neurons by thermogenetic operation is simple and convenient with Drosophila Transient Receptor Potential Ankyrin 1 (dTRPA1), which is a temperature- and voltage-gated cation channel that increases neuronal excitability when the ambient temperature rises above 23 &#176;C33,37; however, testing animals at high temperatures might produce adverse effects on behavior. Another effective approach to activate neurons in Drosophila is using optogenetics with CsChrimson36, which is a red-shifted variant of channelrhodopsin that increases the excitability of neurons when exposed to light. Optogenetics offers higher temporal resolution and lesser disturbance to behaviors than thermogenetics. Combining the quantitative measurement of food intake with the manipulation of neuronal activity represents an effective approach for studying the neural mechanisms of feeding.
We describe in detail the preparation of the feeding chamber and the flies to be tested. Using Taotie-Gal4 flies as a model24, we describe activating neurons by thermogenetics and optogenetics. Two assays of quantification of food consumption with dye-labeled food are also described in the protocol.

<table border="0" cellpadding="0" cellspacing="0" width="942">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:332px;">UAS-CsChrimson</td>
			<td style="width:163px;">Bloomintoon</td>
			<td style="width:176px;">55135</td>
			<td style="width:272px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:332px;">UAS-dTrpA1</td>
			<td style="width:163px;">Bloomintoon</td>
			<td>26263</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TDC1-GAL4&#160;</td>
			<td style="width:163px;">Bloomintoon</td>
			<td style="width:176px;">9312</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:332px;">TDC2-GAL4</td>
			<td style="width:163px;">Bloomintoon</td>
			<td style="width:176px;">9313</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;">sNPF-GAL4</td>
			<td></td>
			<td></td>
			<td style="width:272px;">Provided by Z. Zhao</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NPF-GAL4</td>
			<td></td>
			<td></td>
			<td style="width:272px;">Provided by Y. Rao</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TH-GAL4</td>
			<td></td>
			<td></td>
			<td style="width:272px;">Provided by Y. Rao</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">5-HT-GAL4</td>
			<td></td>
			<td></td>
			<td style="width:272px;">Provided by Y. Rao</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">AKH-GAL4</td>
			<td></td>
			<td></td>
			<td style="width:272px;">Provided by Y. Rao</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">dip2-GAL4</td>
			<td></td>
			<td></td>
			<td>Provided by Y. Rao</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:332px;">Taotie-GAL4</td>
			<td></td>
			<td></td>
			<td>Provided by J. Carlson</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:332px;">Agarose</td>
			<td>Biowest</td>
			<td style="width:176px;">G-10</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:332px;">Sucrose</td>
			<td>Sigma</td>
			<td style="width:176px;">S7903</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Erioglaucine disodium salt</td>
			<td>Sigma</td>
			<td>861146</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">all-trans-retinal&#160;</td>
			<td style="width:163px;">Sigma&#160;</td>
			<td style="width:176px;">R2500</td>
			<td>stored in darkness</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Triton X-100</td>
			<td style="width:163px;">Amresco</td>
			<td>9002-93-01</td>
			<td></td>
		</tr>
		<tr height="146">
			<td height="146" style="height:146px;width:332px;">Fly food</td>
			<td style="width:163px;"></td>
			<td style="width:176px;">1 L food contains: 77.7 g corn meal, 32.19 g yeast, 5 g agar, 0.726 g CaCl2, 31.62 g sucrose, 63.2 g glucose, 2 g potassium sorbate, pH&#160;&#160;&#160;</td>
			<td></td>
		</tr>
		<tr height="92">
			<td height="92" style="height:92px;">&#160;1x PBS buffer&#160;</td>
			<td style="width:163px;"></td>
			<td style="width:176px;">1 L 1X PBS contains: 8 g Nacl, 0.2 g Kcl, 1.44 g Na2HPO4, 0.24 g KH2PO4, pH 7.4</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:332px;">PBST buffer</td>
			<td style="width:163px;"></td>
			<td colspan="2">1X PBS with 1% Triton X-100</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">&#160;Grinding mill</td>
			<td style="width:163px;">Shang Hai Jing Xin</td>
			<td>Tissuelyser-24</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:332px;">Incubator</td>
			<td style="width:163px;">Ning Bo Jiang Nan</td>
			<td>HWS-80</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Magnetic stirrer with a heat plate</td>
			<td style="width:163px;">Chang Zhou Bo Yuan</td>
			<td style="width:176px;">CJJ 78-1</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Spectrometer</td>
			<td style="width:163px;">Thorlabs</td>
			<td style="width:176px;">CCS200/M</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:332px;">Microplate Spectrophotometer</td>
			<td>Thermo Scientific&#160;</td>
			<td style="width:176px;">Multiskan GO Type: 1510, REF 51119200</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fluorescence stereo microscope&#160;</td>
			<td style="width:163px;">Leica</td>
			<td style="width:176px;">&#160;M205FA</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Stereo microscope</td>
			<td style="width:163px;">Leica&#160;</td>
			<td style="width:176px;">S6E</td>
			<td></td>
		</tr>
		<tr height="80">
			<td height="80" style="height:80px;width:332px;">Outside container</td>
			<td>Jiang Su Hai Men</td>
			<td style="width:176px;">glass vial with a diameter of 31.8 mm and a height of 80 mm (inside dimension)</td>
			<td></td>
		</tr>
		<tr height="80">
			<td height="80" style="height:80px;width:332px;">Inside container&#160;</td>
			<td>Beijing Yi Ran machinery factory</td>
			<td style="width:176px;">plastic dish with a diameter of 13.6 mm and a height of 7.5 mm (inside dimension)</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:332px;">1.5 mL Eppendorf tubes</td>
			<td style="width:163px;">Hai Men Ning Mong</td>
			<td style="width:176px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">&#160;96 well plate</td>
			<td style="width:163px;">Corning Incorporated</td>
			<td style="width:176px;">&#160;Costar 3599</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:332px;">LEDs</td>
			<td style="width:163px;">Xin Xing Yuan Guangdian</td>
			<td style="width:176px;">607 nm, 3W&#160;</td>
			<td>https://item.taobao.com/item.htm?id=20158878058</td>
		</tr>
	</tbody>
</table>

combining quantitative food-intake assays and forcibly activating neurons to study appetite in drosophila

Food consumption is under the tight control of the brain, which integrates the physiological status, palatability, and nutritional contents of the food, and issues commands to start or stop feeding. Deciphering the processes underlying the decision-making of timely and moderate feeding carries major implications in our understanding of physiological and psychological disorders related to feeding control. Simple, quantitative, and robust methods are required to measure the food ingestion of animals after experimental manipulation, such as forcibly increasing the activities of certain target neurons. Here, we introduced dye-labeling-based feeding assays to facilitate the neurogenetic study of feeding control in adult fruit flies. We review available feeding assays, and then describe our methods step-by-step from setup to analysis, which combine thermogenetic and optogenetic manipulation of neurons controlling feeding motivation with dye-labeled food intake assay. We also discuss the advantages and limitations of our methods, compared with other feeding assays, to help readers choose an appropriate assay.

Thermogenetic screen.
Abnormally increased appetite causes elevated food intake, regardless of physiological needs. We utilized this scheme to design a high-throughput behavioral screen to obtain genetic handles of neurons related to hunger and satiated states (Figure 1). The screen yielded Taotie-Gal424. When the Taotie-Gal4 neurons were forcibly activated ...

Watch this Scientific Journal Video about Combining Quantitative Food-intake Assays and Forcibly Activating Neurons to Study Appetite in Drosophila at JoVE.com

Combining Quantitative Food-intake Assays and Forcibly Activating Neurons to Study Appetite in Drosophila

Quantitative food-intake assays with dyed food provide a robust and high-throughput means to evaluate feeding motivation. Combining the food consumption assay with thermogenetic and optogenetic screens is a powerful approach to investigate the neural circuits underlying appetite in adult Drosophila melanogaster.

Combining Quantitative Food-intake Assays and Forcibly Activating Neurons to Study Appetite in Drosophila

Food consumption is under the tight control of the brain, which integrates the physiological status, palatability, and nutritional contents of the food, ...

Research

JoVE Journal

Behavior

Stereotaxic Microinjection of Viral Vectors Expressing Cre Recombinase to Study the Role of Target Genes in Cocaine Conditioned Place Preference

Microinjecting recombinant adenoassociated viral (rAAV) vectors expressing Cre recombinase into distinct mouse brain regions to selectively knockout genes ...

A Procedure to Study the Effect of Prolonged Food Restriction on Heroin Seeking in Abstinent Rats

In human drug addicts, exposure to drug-associated cues or environments that were previously associated with drug taking can trigger relapse during ...

Uncovering Beat Deafness: Detecting Rhythm Disorders with Synchronized Finger Tapping and Perceptual Timing Tasks

A set of behavioral tasks for assessing perceptual and sensorimotor timing abilities in the general population (i.e., non-musicians) is presented here ...

Design and Implementation of an fMRI Study Examining Thought Suppression in Young Women with, and At-risk, for Depression

Ruminative brooding is associated with increased vulnerability to major depression. Individuals who regularly ruminate will often try to reduce the ...

Combining Multiple Data Acquisition Systems to Study Corticospinal Output and Multi-segment Biomechanics

Transcranial magnetic stimulation techniques allow for an in-depth investigation into the neural mechanisms that underpin human behavior. To date, the use ...

Feeding Experimentation Device (FED): Construction and Validation of an Open-source Device for Measuring Food Intake in Rodents

Feeding Experimentation Device FED: Construction and Validation of an Open-source Device for Measuring Food Intake in Rodents

Food intake measurements are essential for many research studies. Here, we provide a detailed description of a novel solution for measuring food intake in ...

Application of MultiColor FlpOut Technique to Study High Resolution Single Cell Morphologies and Cell Interactions of Glia in Drosophila

Application of MultiColor FlpOut Technique to Study High Resolution Single Cell Morphologies and Cell Interactions of Glia in Drosophila

Cells display different morphologies and complex anatomical relationships. How do cells interact with their neighbors? Do the interactions differ between ...

Reversible Cooling-induced Deactivations to Study Cortical Contributions to Obstacle Memory in the Walking Cat

On complex, naturalistic terrain, sensory information about an environmental obstacle can be used to rapidly adjust locomotor movements for avoidance. For ...

An Automated Method to Determine the Performance of Drosophila in Response to Temperature Changes in Space and Time

An Automated Method to Determine the Performance of Drosophila in Response to Temperature Changes in Space and Time

Temperature is a ubiquitous environmental factor that affects how species distribute and behave. Different species of Drosophila fruit flies have specific ...

In Vivo Protocol of Controlled Subconcussive Head Impacts for the Validation of Field Study Data

Subconcussive hits pose a threat to neuronal health as they have shown to induce neuronal structural damage and functional impairment without causing ...