The authors would like to thank Dr. Tingwei Mi for helping them optimize the two-choice feeding assay. They would also like to thank Samuel Chan and Wyatt Koolmees for their comments on the manuscript. This project was funded by the National Institutes of Health grants R03 DC014787 (Y.V.Z.) and R01 DC018592 (Y.V.Z.) and by the Ambrose Monell Foundation.

1. Assembling the assay chambers
NOTE: While this protocol describes the use of a 35 mm Petri dish (Figure 1A), the desired effect can be achieved using any watertight, smooth-bottomed vessel that can be bisected and covered.
<ol>
	<li>First, bisect a lidded 35 mm Petri dish by fixing a length of plastic (5 mm in width and 3 mm in height) down the midline with waterproof adhesive, forming two watertight compartments. Confirm that the seal is complete to avoid le...

<ol>
	<li>Jiao, Y., Moon, S. J., Montell, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Drosophila+gustatory+receptor+required+for+the+responses+to+sucrose,+glucose,+and+maltose+identified+by+mRNA+tagging.">A Drosophila gustatory receptor required for the responses to sucrose, glucose, and maltose identified by mRNA tagging.</a> Proceedings of the National Academy of Sciences of the United States of America. 104 (35), 14110-14115 (2007).</li><li>Dahanukar, A., Foster, K., van der Goes van Naters, W. M., 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=A+Gr+receptor+is+required+for+response+to+the+sugar+trehalose+in+taste+neurons+of+Drosophila.">A Gr receptor is required for response to the sugar trehalose in taste neurons of Drosophila.</a> Nature Neuroscience. 4 (12), 1182-1186 (2001).</li><li>Ueno, 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=Trehalose+sensitivity+in+Drosophila+correlates+with+mutations+in+and+expression+of+the+gustatory+receptor+gene+Gr5a.">Trehalose sensitivity in Drosophila correlates with mutations in and expression of the gustatory receptor gene Gr5a.</a> Current Biology. 11 (18), 1451-1455 (2001).</li><li>Fujii, 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=Drosophila+sugar+receptors+in+sweet+taste+perception,+olfaction,+and+internal+nutrient+sensing.">Drosophila sugar receptors in sweet taste perception, olfaction, and internal nutrient sensing.</a> Current Biology. 25 (5), 621-627 (2015).</li><li>Wang, Z., Singhvi, A., Kong, P., 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=Taste+representations+in+the+Drosophila+brain.">Taste representations in the Drosophila brain.</a> Cell. 117 (7), 981-991 (2004).</li><li>Thorne, N., Chromey, C., Bray, S., 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=Taste+perception+and+coding+in+Drosophila.">Taste perception and coding in Drosophila.</a> Current Biology. 14 (12), 1065-1079 (2004).</li><li>Slone, J., Daniels, J., 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=Sugar+receptors+in+Drosophila.">Sugar receptors in Drosophila.</a> Current Biology. 17 (20), 1809-1816 (2007).</li><li>Dus, 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=Nutrient+sensor+in+the+brain+directs+the+action+of+the+brain-gut+axis+in+Drosophila.">Nutrient sensor in the brain directs the action of the brain-gut axis in Drosophila.</a> Neuron. 87 (1), 139-151 (2015).</li><li>Toshima, N., Tanimura, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Taste+preference+for+amino+acids+is+dependent+on+internal+nutritional+state+in+Drosophila+melanogaster.">Taste preference for amino acids is dependent on internal nutritional state in Drosophila melanogaster.</a> Journal of Experimental Biology. 215 (16), 2827-2832 (2012).</li><li>Melcher, C., Bader, R., Pankratz, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amino+acids,+taste+circuits,+and+feeding+behavior+in+Drosophila:+towards+understanding+the+psychology+of+feeding+in+flies+and+man.">Amino acids, taste circuits, and feeding behavior in Drosophila: towards understanding the psychology of feeding in flies and man.</a> Journal of Endocrinology. 192 (3), 467-472 (2007).</li><li>Zhang, Y. V., Ni, J., Montell, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+molecular+basis+for+attractive+salt-taste+coding+in+Drosophila.">The molecular basis for attractive salt-taste coding in Drosophila.</a> Science. 340 (6138), 1334-1338 (2013).</li><li>Weiss, L. A., Dahanukar, A., Kwon, J. Y., Banerjee, D., 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=The+molecular+and+cellular+basis+of+bitter+taste+in+Drosophila.">The molecular and cellular basis of bitter taste in Drosophila.</a> Neuron. 69 (2), 258-272 (2011).</li><li>Moon, S. J., Kottgen, M., Jiao, Y., Xu, H., Montell, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+taste+receptor+required+for+the+caffeine+response+in+vivo.">A taste receptor required for the caffeine response in vivo.</a> Current Biology. 16 (18), 1812-1817 (2006).</li><li>Dweck, H. K. M., 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=Molecular+logic+and+evolution+of+bitter+taste+in+Drosophila.">Molecular logic and evolution of bitter taste in Drosophila.</a> Current Biology. 30 (1), 17-30 (2020).</li><li>Lee, 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=Gustatory+receptors+required+for+avoiding+the+insecticide+L-canavanine.">Gustatory receptors required for avoiding the insecticide L-canavanine.</a> Journal of Neuroscience. 32 (4), 1429-1435 (2012).</li><li>Montell, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+taste+of+the+Drosophila+gustatory+receptors.">A taste of the Drosophila gustatory receptors.</a> Current Opinion in Neurobiology. 19 (4), 345-353 (2009).</li><li>Clyne, P. J., Warr, C. G., 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=Candidate+taste+receptors+in+Drosophila.">Candidate taste receptors in Drosophila.</a> Science. 287 (5459), 1830-1834 (2000).</li><li>Liman, E. R., Zhang, Y. V., Montell, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Peripheral+coding+of+taste.">Peripheral coding of taste.</a> Neuron. 81 (5), 984-1000 (2014).</li><li>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=Gustatory+processing+in+Drosophila+melanogaster.">Gustatory processing in Drosophila melanogaster.</a> Annual Review of Entomology. 63, 15-30 (2018).</li><li>Freeman, E. G., Dahanukar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+neurobiology+of+Drosophila+taste.">Molecular neurobiology of Drosophila taste.</a> Current Opinion in Neurobiology. 34, 140-148 (2015).</li><li>Tanimura, T., Isono, K., Yamamoto, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Taste+sensitivity+to+trehalose+and+its+alteration+by+gene+dosage+in+Drosophila+melanogaster.">Taste sensitivity to trehalose and its alteration by gene dosage in Drosophila melanogaster.</a> Genetics. 119 (2), 399-406 (1988).</li><li>Zhang, Y. V., Raghuwanshi, R. P., Shen, W. L., Montell, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Food+experience-induced+taste+desensitization+modulated+by+the+Drosophila+TRPL+channel.">Food experience-induced taste desensitization modulated by the Drosophila TRPL channel.</a> Nature Neuroscience. 16 (10), 1468-1476 (2013).</li><li>Bantel, A. P., Tessier, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Taste+preference+assay+for+adult+Drosophila.">Taste preference assay for adult Drosophila.</a> Journal of Visualized Experiments: JoVE. (115), e54403 (2016).</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> Journal of Visualized Experiments: JoVE. (3), e193 (2007).</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> Proceedings of the National Academy of Sciences of the United States of America. 104 (20), 8253-8256 (2007).</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> Journal of Visualized Experiments: JoVE. (121), e55024 (2017).</li><li>Ro, J., Harvanek, Z. M., Pletcher, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FLIC:+high-throughput,+continuous+analysis+of+feeding+behaviors+in+Drosophila.">FLIC: high-throughput, continuous analysis of feeding behaviors in Drosophila.</a> PLoS One. 9 (6), 101107 (2014).</li><li>Yoshihara, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+recording+of+calcium+signals+from+identified+neurons+and+feeding+behavior+of+Drosophila+melanogaster.">Simultaneous recording of calcium signals from identified neurons and feeding behavior of Drosophila melanogaster.</a> Journal of Visualized Experiments: JoVE. (62), e3625 (2012).</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> Nature Methods. 11 (5), 535-540 (2014).</li><li>Yapici, N., Cohn, R., Schusterreiter, C., Ruta, V., Vosshall, L. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+taste+circuit+that+regulates+ingestion+by+integrating+food+and+hunger+signals.">A taste circuit that regulates ingestion by integrating food and hunger signals.</a> Cell. 165 (3), 715-729 (2016).</li><li>Jiang, L., Zhan, Y., 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=Combining+quantitative+food-intake+assays+and+forcibly+activating+neurons+to+study+appetite+in+Drosophila.">Combining quantitative food-intake assays and forcibly activating neurons to study appetite in Drosophila.</a> Journal of Visualized Experiments: JoVE. (134), e56900 (2018).</li><li>Moon, S. J., Lee, Y., Jiao, Y., Montell, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Drosophila+gustatory+receptor+essential+for+aversive+taste+and+inhibiting+male-to-male+courtship.">A Drosophila gustatory receptor essential for aversive taste and inhibiting male-to-male courtship.</a> Current Biology. 19 (19), 1623-1627 (2009).</li><li>Zhang, Y. V., Aikin, T. J., Li, Z., Montell, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+basis+of+food+texture+sensation+in+Drosophila.">The basis of food texture sensation in Drosophila.</a> Neuron. 91 (4), 863-877 (2016).</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> Nature Communications. 5, 4560 (2014).</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> Molecular Brain. 8, 87 (2015).</li><li>Simpson, J. H., Looger, L. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+imaging+and+optogenetics+in+Drosophila.">Functional imaging and optogenetics in Drosophila.</a> Genetics. 208 (4), 1291-1309 (2018).</li></ol>

The authors declare no conflicts of interest or competing financial interests.

This method involves several crucial steps where problems can occur. First, make sure flies ingest a sufficient amount of food to provide stable data. If flies eat poorly, ensure that the flies have been wet-starved for at least 24 h, and that the experimental media contains at least a minimal sucrose concentration (2 mM). To further stimulate food consumption, prolong the wet-starvation period beyond 24 h, depending on the flies&#39; physiological condition. If too many flies fail to survive the prolonged starvation, en...

Despite dramatic differences in the anatomical structure of taste organs between flies and mammals, the flies&#39; behavioral responses to many tastant substances are strikingly similar to those of mammals. For example, flies prefer sugar1,2,3,4,5,6,7,8, amino acids9,10, and low salt11, which indicate nutrients, but reject bitter foods12,13,14,15 that are unpalatable or toxic. Over the past two decades, flies have proven to be a highly valuable model organism for advancing the understanding of many fundamental questions related to taste sensation and food consumption, including tastant detection, taste transduction, taste plasticity, and feeding regulation16,17,18,19,20. Remarkably, a number of studies have demonstrated that the taste transduction and neural circuit mechanisms underlying taste perception are analogous between fruit flies and mammals. Therefore, the fruit fly serves as an ideal experimental organism, enabling researchers to uncover evolutionarily conserved concepts and principles that govern food detection and consumption in the animal kingdom.
To investigate taste sensation in flies, it is critical to establish a fast and rigorous assay to objectively measure food preference. Over the years, various feeding methods, such as dye-based assays11,12,13,21,22,23, the fly proboscis extension response assay24, the Capillary Feeder (CAFE) assay25,26, the Fly Liquid-Food Interaction Counter (FLIC) assay27, and other combinatorial methods have been developed to quantitatively measure food preference and/or food intake for fruit flies28,29,30,31. One of the popular feeding paradigms is the dye-based two-choice feeding assay using either a multiwell microtiter plate12,21,32 or, as described here, a small Petri dish11,22 as the feeding chamber. This assay is designed based on the transparency of the fly&#39;s abdomen. During this assay, flies are placed into the feeding chamber and presented with two food options mixed with either red dye or blue dye. Once the assay is complete, fly abdomens appear red or blue depending on which food they have consumed.
Both the Petri-dish and the multiwell-plate dye-based feeding assays are highly robust and yield approximately the same results. Using these two assays, numerous important discoveries and breakthroughs have been made toward deciphering the highly diversified receptors and cells responsible for sensing food tastes and food texture11,12,21,22,32,33. In the dye-based assay, one experimental step requiring considerable time and effort is preparing and loading food into the feeding chamber. To reduce the food preparation and loading time, this assay was modified by replacing the multiwell microtiter plate with a small Petri dish, which is divided into two equal compartments. In the Petri-dish-based assay, two different foods supplemented with blue or red dye are added to the two halves of the dish. Then, ~70 prestarved, 2-4-day-old flies are placed in the dish and allowed to choose between blue and red foods in the dark for about 90 min. The abdomen of each fly is then examined, and the preference index (PI) is calculated.
This Petri-dish-based two-choice feeding assay is affordable, simple, and fast. One multiwell plate requires approximately 110 s to fill, whereas each Petri dish takes only ~20 s. In addition, the multiwell plate requires pipetting small volumes of food into a large number of small wells (e.g., 60 or more wells per plate), which demands considerable precision and attention. Conversely, the Petri-dish-based assay requires only two actions per plate. As the feeding assay can involve a large number of replicates, the Petri-dish-based assay saves a nontrivial amount of time and effort. This assay gives results equivalent to those from the multiwell-based assay and has proven successful in addressing many fundamental questions in taste sensation, including salt taste coding11, taste plasticity modified by food experience22, and the molecular basis of food texture sensation33. In summary, this Petri-dish-based two-choice assay is a powerful tool to investigate how flies perceive external and internal nutrient milieus to elicit appropriate feeding behavior.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>35 mm Petri dish</td>
			<td>Fisher Scientific</td>
			<td>08-772E</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Thomas Scientific</td>
			<td>C756P56</td>
			<td></td>
		</tr>
		<tr>
			<td>Clear adhesive</td>
			<td>Fisher Scientific</td>
			<td>NC9884114</td>
			<td></td>
		</tr>
		<tr>
			<td>Conical centrifuge tubes</td>
			<td>Fisher Scientific</td>
			<td>05-527-90</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissection microscope</td>
			<td>Amscope</td>
			<td>SM-2T-6WB-V331</td>
			<td></td>
		</tr>
		<tr>
			<td>FCF Brilliant Blue</td>
			<td>Wako Chemical</td>
			<td>3844-45-9</td>
			<td></td>
		</tr>
		<tr>
			<td>Fly CO2 anesthesia setup</td>
			<td>Genesee Scientfic</td>
			<td>59-114/54-104M</td>
			<td></td>
		</tr>
		<tr>
			<td>Fly incubator with programmable day/night cycle</td>
			<td>Powers Scientific Inc.</td>
			<td>IS33SD</td>
			<td></td>
		</tr>
		<tr>
			<td>Fly lines</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glass dish (microwave-safe)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>Fisher Scientific</td>
			<td>06-666A</td>
			<td></td>
		</tr>
		<tr>
			<td>Media storage bottle</td>
			<td>Fisher Scientific</td>
			<td>50-192-9998</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic divider cut to fit the dish from a sheet no thicker than 5 mm</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic fly vials</td>
			<td>Genesee Scientific</td>
			<td>32-116</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Millipore Sigma</td>
			<td>S9378</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulforhodamine B</td>
			<td>Millipore Sigma</td>
			<td>S9012</td>
			<td></td>
		</tr>
		<tr>
			<td>Tastant compound of interest</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex mixer</td>
			<td>Benchmark Scientific</td>
			<td>BV1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath</td>
			<td>Fisher Scientific</td>
			<td>FSGPD05</td>
			<td></td>
		</tr>
	</tbody>
</table>

a rapid food-preference assay in drosophila

To select food with nutritional value while avoiding the consumption of harmful agents, animals need a sophisticated and robust taste system to evaluate their food environment. The fruit fly, Drosophila melanogaster, is a genetically tractable model organism that is widely used to decipher the molecular, cellular, and neural underpinnings of food preference. To analyze fly food preference, a robust feeding method is needed. Described here is a two-choice feeding assay, which is rigorous, cost-saving, and fast. The assay is Petri-dish-based and involves the addition of two different foods supplemented with blue or red dye to the two halves of the dish. Then, ~70 prestarved, 2-4-day-old flies are placed in the dish and&#160;allowed to choose between blue and red foods in the dark for about 90 min. Examination of the abdomen of each fly is followed by the calculation of the preference index. In contrast to multiwell plates, each Petri dish takes only ~20 s to fill and saves time and effort. This feeding assay can be employed to quickly determine whether flies like or dislike a particular food.

In this assay, a 35 mm dish was divided into two equal feeding compartments, with each half of the dish containing agarose food coupled with either blue or red dye (Figure 1A). To exclude dye bias, the blue and red dye concentrations were carefully refined to yield an approximate &#34;0&#34; PI when only these two dyes were added (Figure 1B). Once the Petri dish was loaded with tested food, ~70 wet-starved, 2-4-day-old adult flies were transferred to the dish, a...

Watch this Scientific Journal Video about A Rapid Food-Preference Assay in Drosophila at JoVE.com

A Rapid Food-Preference Assay in Drosophila

We present a protocol for a two-choice feeding assay for flies. This feeding assay is fast and easy to run and is suitable not only for small-scale laboratory research, but also for high-throughput behavioral screens in flies.

A Rapid Food-Preference Assay in Drosophila

To select food with nutritional value while avoiding the consumption of harmful agents, animals need a sophisticated and robust taste system to evaluate ...

Our protocol is designed to perform a fine assay for the fruit fly, which is a powerful model organism that enables to design for all the genes, receptors, neurons and a neuro-psych heads that are involved in test sensation and food-consumption. Like humans fly like food that tastes:sweet, slightly-salty, slightly-sour or reject food that tastes bitter, too salty or too sour. The power of this technique comes from the speed and convenience.You can test many different flies in a short time PRH without a complex setup. Our method is an excellent, excellent assay for understanding whether flies like a, just like a particular food, as well as how certain gene products influence taste preference. Establishing whether animals accept or reject certain foods can be challenging.Therefore it's important to establish a standard protocol for testing animal taste preference. To prepare starvation vials for the assay, loosely compact a piece of tissue at the bottom of each empty plastic fly vial per fly gene type to be tested. Such that the paper fills this space without forming a dense mass, at about three milliliters of pure water to each vial to completely saturate the tissues without standing water.Taking care that there are no large droplets of excess water on the walls of the vials. Alternatively five milliliters of 1%Agros without sucrose can be substituted for the soaked paper, 24 hours before the experiment carbon dioxide anesthetized two to four day old flies and sort the flies into groups of approximately 70. Then add each group of flies to a starvation vile and label each vial with the genotype and time of starvation initiation.Before performing an experiment, prepare a range of dilutions for each dye using the same food with each different dye color. Combined 0.5 grams of Agros with 50 milliliters of pure water in a microwave safe vessel and heat the Agro solution until it has dissolved stirring as necessary. Dissolve each food component, including sucrose and any experimental compounds in water at a 100 fold or higher concentration of the final tested concentration.And mix the Agro dye and desired experimental compound in conical, polypropylene centrifuge tubes. After mixing place the tubes in the 60 degrees Celsius water bath until distribution and add one milliliter of one color of the experimental food and dye solutions to one side of the first assay dish. Allow the Agros to cool until firm before adding one milliliter of the control food solution, labeled with the second dye color to the other side of the dish.Then repeat the assay dish preparation, with the opposite control and experimental dye solution pair. Use the results to identify two dye concentrations that yield a preference index of zero. When no experimental compound is added.To perform a two-way feeding assay. First temporarily paralyzed one experimental fly vile for three to five minutes on ice until no obvious motor activities such as flying and climbing are observed. Once the flies have been immobilized, gently invert the vial and tap to transfer the flies into the assay chamber then quickly placed the lid onto the chamber.When all of the groups have been transferred move all of the assay chambers to a dark and closed space for 90 minutes. At the end of the assay invert the chambers at a minus 20 degrees Celsius freezer, for about an hour. Before placing each chamber under a stereo microscope to examine the abdominal color of the flies in each experimental group.Count a fly, if the abdomen is more than 50%colored indicating a robust feeding, discard any flies in which the abdomen contains only a tiny food spot, which is indicative of poor eating. When all of the flies have been counted use the equation to quantify the food preference index for each group. In this assay, a 35 millimeter dish was divided into two week we'll feed in compartments containing Agro's food, coupled with red or blue dye.To exclude dye bias, the blue and red dye concentrations were carefully refined to yield an approximate zero preference when only these two dyes were added, 90 minutes after wet starved adult fly loading bly abdominal colors appeared as blue or red. If the animal predominantly consumed blue or red food, respectively, if a fly consumed both blue and red, the abdomen appeared purple. Only flies that ingested a considerable amount of food were scored, while flies with an insufficient food intake were not counted.Comparing this Petri dish based assay to the multi-well plate based assay revealed that the two feeding methods gave essentially the same assaying feeding results in response to sweet, bitter, and salty food in wild type flies. Notably, however it is much faster to prepare and distribute food in a Petri dish than in a 60 well multi-well plate. Be sure to identify what dye concentration to use especially after making a new diet batch.This concentration can be different between fly lines. Our pair today is based two-choice assay is very powerful too. For you asking how the flies, sense both internal-external frame damaged to real state appropriate feeding and behavior.

a-rapid-food-preference-assay-in-drosophila

Research

JoVE Journal

Neuroscience

5.8K Görüntüleme.  Monell Chemical Senses Center. Protokolümüz, test hissi ve gıda tüketiminde yer alan tüm genler, reseptörler, nöronlar ve nöro-psikolojik kafalar için tasarım yapmayı sağlayan güçlü bir model organizma olan meyve sineği için ince bir test yapmak üzere tasarlanmıştır. İnsanların tadı olan yiyecekler gibi uçması gibi:tatlı, hafif tuzlu, hafif ekşi veya acı, çok tuzlu veya çok ekşi tadı olan yiyecekleri reddedin. Bu tekniğin gücü hız ve kolaylıktan gelir.Karmaşık bir kurulum olma...