We thank Sarah Wu and Camille Graham for developing early phases of the cold probe assay, the Bloomington Drosophila Stock Center for fly stocks, and Galko lab members for critically reading the manuscript. This work was supported by NIH NRSA (NIH F31NS083306) to HNT, and by NIH R01NS069828, R21NS087360 and a University of Texas MD Anderson Clark Fellowship in Basic Research to MJG.

1. Preparation of Larvae
<ol>
	<li>Raise stocks or genetic crosses in a 25 &#186;C incubator.
	<ol>
		<li>If culturing a cross, use 20-25 virgin females and 15-20 males per vial containing regular cornmeal fly media. Allow females to lay eggs for approximately 48 h before transferring them to a new vial of food.</li>
	</ol>
	</li>
	<li>4-5 days after egg lay, collect 3rd instar larvae of the desired genotype by gently squirting a stream of water into the mushy food and larvae, and pour out the contents into ...

<ol>
	<li>Grueber, W. B., Jan, L. Y., Jan, Y. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tiling+of+the+Drosophila+epidermis+by+multidendritic+sensory+neurons.">Tiling of the Drosophila epidermis by multidendritic sensory neurons.</a> Development. 129 (12), 2867-2878 (2002).</li><li>Gao, F. B., Brenman, J. E., Jan, L. Y., Jan, Y. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genes+regulating+dendritic+outgrowth,+branching,+and+routing+in+Drosophila.">Genes regulating dendritic outgrowth, branching, and routing in Drosophila.</a> Genes Dev. 13 (19), 2549-2561 (1999).</li><li>Sweeney, S. T., Broadie, K., Keane, J., Niemann, H., O'Kane, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+expression+of+tetanus+toxin+light+chain+in+Drosophila+specifically+eliminates+synaptic+transmission+and+causes+behavioral+defects.">Targeted expression of tetanus toxin light chain in Drosophila specifically eliminates synaptic transmission and causes behavioral defects.</a> Neuron. 14 (2), 341-351 (1995).</li><li>Hwang, R. 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=Nociceptive+neurons+protect+Drosophila+larvae+from+parasitoid+wasps.">Nociceptive neurons protect Drosophila larvae from parasitoid wasps.</a> Curr Biol. 17 (24), 2105-2116 (2007).</li><li>Im, S. H., Galko, M. 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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=The+TRP+Channels+Pkd2,+NompC,+and+Trpm+Act+in+Cold-Sensing+Neurons+to+Mediate+Unique+Aversive+Behaviors+to+Noxious+Cold+in+Drosophila.">The TRP Channels Pkd2, NompC, and Trpm Act in Cold-Sensing Neurons to Mediate Unique Aversive Behaviors to Noxious Cold in Drosophila.</a> Curr Biol. , (2016).</li><li>Kernan, M., Cowan, D., Zuker, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+dissection+of+mechanosensory+transduction:+mechanoreception-defective+mutations+of+Drosophila.">Genetic dissection of mechanosensory transduction: mechanoreception-defective mutations of Drosophila.</a> Neuron. 12 (6), 1195-1206 (1994).</li><li>Tsubouchi, A., Caldwell, J. C., Tracey, W. 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I., Laurent, G., Benzer, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=painless,+a+Drosophila+gene+essential+for+nociception.">painless, a Drosophila gene essential for nociception.</a> Cell. 113 (2), 261-273 (2003).</li><li>Babcock, D. T., Landry, C., Galko, 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=Cytokine+signaling+mediates+UV-induced+nociceptive+sensitization+in+Drosophila+larvae.">Cytokine signaling mediates UV-induced nociceptive sensitization in Drosophila larvae.</a> Curr Biol. 19 (10), 799-806 (2009).</li><li>Chattopadhyay, A., Gilstrap, A. V., Galko, M. 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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+sensory+feedback+circuit+coordinates+muscle+activity+in+Drosophila.">A sensory feedback circuit coordinates muscle activity in Drosophila.</a> Mol Cell Neurosci. 35 (2), 383-396 (2007).</li><li>Zhong, L., Hwang, R. Y., Tracey, W. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pickpocket+is+a+DEG/ENaC+protein+required+for+mechanical+nociception+in+Drosophila+larvae.">Pickpocket is a DEG/ENaC protein required for mechanical nociception in Drosophila larvae.</a> Curr Biol. 20 (5), 429-434 (2010).</li><li>Xiang, 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=Light-avoidance-mediating+photoreceptors+tile+the+Drosophila+larval+body+wall.">Light-avoidance-mediating photoreceptors tile the Drosophila larval body wall.</a> Nature. 468 (7326), 921-926 (2010).</li><li>Neely, G. 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=TrpA1+regulates+thermal+nociception+in+Drosophila.">TrpA1 regulates thermal nociception in Drosophila.</a> PLoS One. 6 (8), e24343 (2011).</li><li>Zhou, Y., Cameron, S., Chang, W. T., Rao, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+directional+change+after+mechanical+stimulation+in+Drosophila.">Control of directional change after mechanical stimulation in Drosophila.</a> Mol Brain. 5, 39 (2012).</li><li>Im, S. H., 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=Tachykinin+acts+upstream+of+autocrine+Hedgehog+signaling+during+nociceptive+sensitization+in+Drosophila.">Tachykinin acts upstream of autocrine Hedgehog signaling during nociceptive sensitization in Drosophila.</a> Elife. 4, e10735 (2015).</li><li>Babcock, D. T., 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=Hedgehog+signaling+regulates+nociceptive+sensitization.">Hedgehog signaling regulates nociceptive sensitization.</a> Curr Biol. 21 (18), 1525-1533 (2011).</li><li>Berrigan, D., Pepin, D. 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The assay described here can be used to qualitatively and quantitatively assess nociception or nociceptive sensitization in larvae of&#160;various genetic backgrounds, environmental influences, and/or damage-induced conditions. Since this assay allows for focal application of a cold stimulus, with this tool one can assess the function of a subset of peripheral sensory neurons specifically in responding to cold temperatures. Interestingly, these cold-evoked behaviors seem to utilize different classes of sensory neurons th...

Drosophila has proven to be highly useful for the identification of novel conserved genes and neuronal circuits that underlie complex behaviors. Flies provide a sophisticated genetic toolkit and a simplified nervous system that allow for precise genetic and neuronal manipulation1,2,3,4 to dissect the cellular and molecular bases of nociception5,6,7. Larvae are particularly useful for these analyses, given that behavioral assays for gentle touch8,9,10, noxious heat11,12,13 and mechanical sensation of noxious stimuli4,11 have already been established, and the transparent larval cuticle allows for live or fixed imaging of the epidermis and underlying sensory neurons. Recently, an assay for noxious cold has also been developed7, which we describe in more detail here.
Using a fine, conical-tipped cold probe, we show that Drosophila larvae exhibit a set of cold-specific reactive behaviors, distinct from behaviors observed during normal locomotion, following gentle touch, or after harsh mechanical or high temperature stimuli7,8,11. The cold-specific behaviors include a robust full-body contraction (CT), a 45-90&#186; raise of the posterior segments (PR) and a simultaneous raise of the anterior and posterior segments into a U-Shape (US). The prevalence of these behaviors increases with decreasing temperatures but each peaks at slightly different cold temperatures. Recent work suggests that CT responses are mediated by different peripheral sensory neurons than those that respond to noxious heat or harsh mechanical stimuli7.
Much like vertebrate nociceptors, Drosophila multiple dendritic (md) peripheral sensory neurons have complex dendritic structures that arborize over the epidermis1. md neurons are present in every larval body segment, projecting their axons to the ventral nerve cord14. md sensory neurons are separated into four different classes (I-IV) based on dendritic morphology and have varying sensory functions4,9,10,15,16,17. While class IV neurons are required for larval lateral body roll responses to high temperatures or harsh mechanical stimuli4, class III neurons are required for gentle touch responses9,10 and are not only activated by cold, but also are required for the cold-evoked behavioral responses7. Both class III and class IV neurons utilize discrete transient receptor potential (TRP) channels to facilitate behavioral responses to noxious7,11,18 and non-noxious stimuli9,10,17,19. Further, larval nociception is sensitized following injury, at the cellular20 and behavioral levels12,21.
The assay described here allows for the quantification of either normal, or potentially altered behavioral responses to cold temperatures ranging from noxious cold (&#8804; 10 &#186;C), innocuous cool (11-17 &#186;C), to ambient temperatures (18-22 &#186;C). The cold temperatures used in this assay are capable of directly activating class III sensory neurons, eliciting robust, reproducible calcium increases and cold-evoked behavioral responses, which can be qualitatively and quantitatively analyzed7. This assay can be applied to larvae of virtually any genotype as well as to&#160;larvae exposed to diverse environmental conditions (altered nutrition, injury, pharmacological agents) to determine both genetic and environmental factors that impact cold nociception, nociceptive sensitization or nociceptive plasticity. Given that thermosensation is ubiquitous across many species, this assay provides a valuable tool for the study of nociception and may uncover novel gene targets or neuronal interactions that will improve our understanding of vertebrate nociception.
The custom-built cold probe (see cold probe, Table of Materials) utilizes a closed loop temperature controlled Peltier device, which cools the aluminum shaft and conical tip through thermal conduction. A thermistor is embedded inside the aluminum conical tip&#160;reports the real-time temperature on the control unit. A heat sink and fan are attached to the thermoelectric module to regulate the Peltier effect&#39;s heat load (Qc) so the desired temperature range of (22-0 &#176;C) can be achieved (see Thermal Control Unit, Table of Materials). The noxious cold stimulus of the cold probe tip is applied by hand to the dorsal midline, to segment(s) equidistant from anterior and posterior ends (roughly segment A4, see Figure 1A) of the larva. In response to cold stimuli, larvae generally produce one of three cold-evoked behaviors within a 10 s&#160;cutoff: a full body contraction (CT), a 45-90&#186; raise of anterior and posterior segments into a U-Shape (US), or a raise of the posterior segments (PR) (described in Results). None of these behaviors are performed during normal peristaltic locomotion or foraging behavior. These behaviors are also distinct from gentle touch responses and the aversive rolling response to high temperature or noxious mechanical stimuli.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Cold Probe</td>
			<td style="width:71px;">Pro-Dev Engineering</td>
			<td style="width:119px;">Custom-built on demand</td>
			<td style="width:167px;">Part numbers and construction details can be provided on request</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Thermal Control Unit</td>
			<td style="width:71px;">TE Technology</td>
			<td style="width:119px;">Custom Built enclosure</td>
			<td style="width:167px;">Part numbers and construction details can be provided on request</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Zeiss Stemi 2000 microscope</td>
			<td style="width:71px;">Zeiss</td>
			<td style="width:119px;">NT55-605</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Fiber-Lite MI-150 High Intensity Illuminator</td>
			<td style="width:71px;">Dolan-Jenner Industries.</td>
			<td style="width:119px;">A20500</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Schott Dual Gooseneck 23 inch Fiber Optic Light Guide</td>
			<td style="width:71px;">Schott North America, Inc.</td>
			<td style="width:119px;">Schott A08575</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="147">
			<td height="147" style="height:147px;width:216px;">Forceps</td>
			<td style="width:71px;">FST</td>
			<td style="width:119px;">FS-1670</td>
			<td style="width:167px;">Used to sort and handle larvae. Be sure to smooth and blunt forceps tips slightly to lower the risk of accidently puncturing or injuring the larvae</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Paintbrush</td>
			<td style="width:71px;">Dick Blick Art Materials</td>
			<td style="width:119px;">06762-1002</td>
			<td style="width:167px;">Used to sort and handle larvae. It is helpful if the paintbrush is damp during use.</td>
		</tr>
		<tr height="20">
			<td height="40" style="height:40px;width:216px;">35 X 10 mm Polystyrene Petri Dish</td>
			<td rowspan="2" style="width:71px;">Falcon</td>
			<td rowspan="2" style="width:119px;">351008</td>
			<td rowspan="2" style="width:167px;"></td>
		</tr>
		<tr height="20">
			<td height="40" style="height:40px;width:216px;">60 X 10 mm Polystyrene Petri Dish</td>
			<td rowspan="2" style="width:71px;">Falcon</td>
			<td rowspan="2" style="width:119px;">351007</td>
			<td rowspan="2" style="width:167px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Piece of black vinyl (at least 2 x 2 inches)</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Used to provide contrast and orient larvae to the cold probe</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Fisherbrand Scoopula Spatula</td>
			<td style="width:71px;">Fisher Scientific</td>
			<td style="width:119px;">14-357Q</td>
			<td style="width:167px;">Used to move food</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Kimtech Science Kimwipes</td>
			<td style="width:71px;">Fisher Scientific</td>
			<td style="width:119px;">06-666A</td>
			<td style="width:167px;">Used to dry the larvae and cold probe if there is excess moisture</td>
		</tr>
	</tbody>
</table>

novel assay for cold nociception in drosophila larvae

How organisms sense and respond to noxious temperatures is still poorly understood. Further, the mechanisms underlying sensitization of the sensory machinery, such as in patients experiencing peripheral neuropathy or injury-induced sensitization, are not well characterized. The genetically tractable Drosophila model has been used to study the cells and genes required for noxious heat detection, which has yielded multiple conserved genes of interest. Little is known however about the cells and receptors important for noxious cold sensing. Although, Drosophila does not survive prolonged exposure to cold temperatures (&#8804;10 &#186;C), and will avoid cool, preferring warmer temperatures in behavioral preference assays, how they sense and possibly avoid noxious cold stimuli has only recently been investigated.
Here we describe and characterize the first noxious cold (&#8804;10 &#186;C) behavioral assay in Drosophila. Using this tool and assay, we show an investigator how to qualitatively and quantitatively assess cold nociceptive behaviors. This can be done under normal/healthy culture conditions, or presumably in the context of disease, injury or sensitization. Further, this assay can be applied to larvae selected for desired genotypes, which might impact thermosensation, pain, or nociceptive sensitization. Given that pain is a highly conserved process, using this assay to further study&#160;thermal nociception will likely glean important understanding of pain processes in other species, including vertebrates.

Drosophila larvae move with a peristaltic motion that includes occasional pauses, head turns, and changes in direction22. In response to focal application of a noxious cold stimulus however, larvae exhibit a set of unique behaviors, unlike the aversive lateral roll to noxious heat and mechanical stimuli. These behaviors are also different from responses to gentle touch8,9,<sup class="xre...

Watch this Scientific Journal Video about Novel Assay for Cold Nociception in Drosophila Larvae at JoVE.com

Novel Assay for Cold Nociception in Drosophila Larvae

Here we demonstrate a novel assay to study cold nociception in Drosophila larvae. This assay utilizes a custom-built Peltier probe capable of applying a focal noxious cold stimulus and results in quantifiable cold-specific behaviors. This technique will allow further cellular and molecular dissection of cold nociception.

Novel Assay for Cold Nociception in Drosophila Larvae

How organisms sense and respond to noxious temperatures is still poorly understood. Further, the mechanisms underlying sensitization of the sensory ...

The overall goal of this noxious cold assay is to be able to quantitate and assess changes in innocuous to noxious cold detection. This method can help answer key questions in the nociception field, including facilitating identification of novel, conserved, cold nociception genes and modulators of pain responses in disease and or injury. The main advantage of this technique is it allows for precise manipulation of the noxious cold stimulus and quantification of cold evoked responses over a variety of environmental and genetics contexts.Generally individuals new to this method will need to practice consistent application of the probe before beginning an experiment. We first had the idea for this method when we found the that drosophila larvae respond to noxious heat and we became curious about whether they do the same to noxious cold. Raise stocks or genetic crosses of drosophila in a 25 degrees Celsius incubator.Note, if culturing a cross, use 20 to 25 virgin females and 15 to 20 males per vial containing regular corn meal fly media and culture for approximately 48 hours before transferring flies to a new vial of food. Five days after the culture is started, collected third instar larvae of the desired genotype by gently squirting a stream of water into the mushy food and larvae. Then pour out the contents into a medium sized clean Petri Dish.Next, gently sort larvae by size, using forceps to preclude larger, wandering third instar, or small, sickly larvae from being tested. Discard larvae containing any undesired genetic markers or balancers. Have another lab member label containers where sorted larvae will be placed to keep the experimenter blind to the experimental condition or genotype of the larvae.Use a scoopula to transfer a small amount of fresh food into a clean labeled Petri Dish filled halfway with room temperature water. Finally, use forceps to gently move the sorted larvae onto the food to prevent starvation or dessication, if testing is anticipated to take more than 20 minutes. Begin by turning on the cold probe unit and allow it a few minutes to cool to the desired temperature.Wipe away any excess moisture on the probe with a laboratory wipe. When not in immediate use, place an insulating cap on the probe to both insulate and keep the tip clean and prevent damage. Next, place a middle third instar larva onto a thin piece of dark movable vinyl to help with contrast visualization and alignment of the probe.Then, place this piece of vinyl with the larva under a bright field microscope. Adjust the microscope and light unit to medium brightness to provide contrast and prevent the larva from drying out too quickly. Using a damp paintbrush, ensure that the larva is moist from the Petri Dish water so that it will not stick to the vinyl and remove any excess water surrounding it using a KimWipe.Advanced the probe by hand towards the larva at a 90 degree angle to the anteroposterior body axis, using the vinyl to move the larva into correct position. The orient the tip of the probe to gently lay across the mid-dorsal surface of the larva with the probe at approximately a 45 degree angle to the microscope stage. Upon probe contact, start a timer.Apply enough downward pressure to slightly indent the surface of the larval cuticle, while still allowing forward or backward movement. Next, hold the probe in place for up to 10 seconds or until a cold evoked behavioral response is observed, whichever occurs first. Then, remove the probe.Record the observed behavioral response and latency of the response. Take note of any non-responders or larvae that do not respond within 10 seconds. Finally, discard the larva and prepare the next.Repeat the procedure until the desired number of test larvae is reached. After contact with the cold probe, results from this experiment indicate that the larvae respond with the following cold-evoked behaviors, crunching their anterior and posterior segments towards the center of their body in a contraction, CT, raising of their anterior and posterior segments into the air to make a U-Shape, US, raising only the posterior segments into the air, PR.Furthermore, different behaviors peak over varying cold ranges such that PR and US peak at three to eight degrees Celsius, while CT peaks around nine to 14 degrees Celsius. Lastly, when comparing latencies of the different cold behaviors, these data show that CT responses were significantly different from PR and US at three degrees Celsius and 10 degrees Celsius and from US at 20 degrees Celsius.Once mastered, this technique can be completed in approximately 30 to 40 minutes for one set of 30 larvae. While attempting this procedure, it's important to be aware of abnormal locomotion, the moisture level of the larva, and the pressure and placement of the cold probe onto the larva. Visual demonstration of this method is critical as improper application of the cold probe could result in different dose response curves or a lack of the cold response behavior.Following this procedure, other methods can be used, such as fluorescent light imaging, gene expression analysis and behavioral assays. All will determine how cold exposure effects cellular activity, morphology, gene expression, or other behaviors. This technique paves the way for researchers in the field of cold nociception to study the genetic, environmental, and disease effects in drosophila.After watching this video, you should have a good understanding of how to use the cold probe tool and assay to analyze cold-evoked responses and understand the cellular and genetic mechanisms of cold nociception.

novel-assay-for-cold-nociception-in-drosophila-larvae

Research

JoVE Journal

Neuroscience

Local and Global Methods of Assessing Thermal Nociception in Drosophila Larvae

In this article, we demonstrate assays to study thermal nociception in Drosophila larvae. One assay involves spatially-restricted (local) stimulation of thermal nociceptors1,2 while the second involves a wholesale (global) activation of most or all such neurons3. Together, these techniques allow visualization and quantification of the behavioral functions of Drosophila nociceptive sensory neurons.
The Drosophila larva is an established model system to study thermal nociception, a sensory response to potentially harmful temperatures that is evolutionarily conserved across species1,2. The advantages of Drosophila for such studies are the relative simplicity of its nervous system and the sophistication of the genetic techniques that can be used to dissect the molecular basis of the underlying biology4-6 In Drosophila, as in all metazoans, the response to noxious thermal stimuli generally involves a "nocifensive" aversive withdrawal to the presented stimulus7. Such stimuli are detected through free nerve endings or nociceptors and the amplitude of the organismal response depends on the number of nociceptors receiving the noxious stimulus8. In Drosophila, it is the class IV dendritic arborization sensory neurons that detect noxious thermal and mechanical stimuli9 in addition to their recently discovered role as photoreceptors10. These neurons, which have been very well studied at the developmental level, arborize over the barrier epidermal sheet and make contacts with nearly all epidermal cells11,12. The single axon of each class IV neuron projects into the ventral nerve cord of the central nervous system11 where they may connect to second-order neurons that project to the brain.
Under baseline conditions, nociceptive sensory neurons will not fire until a relatively high threshold is reached. The assays described here allow the investigator to quantify baseline behavioral responses or, presumably, the sensitization that ensues following tissue damage. Each assay provokes distinct but related locomotory behavioral responses to noxious thermal stimuli and permits the researcher to visualize and quantify various aspects of thermal nociception in Drosophila larvae. The assays can be applied to larvae of desired genotypes or to larvae raised under different environmental conditions that might impact nociception. Since thermal nociception is conserved across species, the findings gleaned from genetic dissection in Drosophila will likely inform our understanding of thermal nociception in other species, including vertebrates.

Local and Global Methods of Assessing Thermal Nociception in Drosophila Larvae

In this article, we demonstrate assays to study thermal nociception in Drosophila larvae. One assay involves spatially-restricted (local) stimulation of thermal nociceptors1,2 while the second involves a wholesale (global) activation of most or all such neurons3. Together, these techniques allow visualization and quantification of the behavioral functions of Drosophila nociceptive sensory neurons.

In this article, we demonstrate assays to study thermal nociception in Drosophila larvae. One assay involves spatially-restricted (local) stimulation of ...

Visualization of Proprioceptors in Drosophila Larvae and Pupae

Proprioception is the ability to sense the motion, or position, of body parts by responding to stimuli arising within the body. In fruitflies and other insects proprioception is provided by specialized sensory organs termed chordotonal organs (ChOs) 2. Like many other organs in Drosophila, ChOs develop twice during the life cycle of the fly. First, the larval ChOs develop during embryogenesis. Then, the adult ChOs start to develop in the larval imaginal discs and continue to differentiate during metamorphosis.
The development of larval ChOs during embryogenesis has been studied extensively 10,11,13,15,16. The centerpiece of each ChO is a sensory unit composed of a neuron and a scolopale cell. The sensory unit is stretched between two types of accessory cells that attach to the cuticle via specialized epidermal attachment cells 1,9,14. When a fly larva moves, the relative displacement of the epidermal attachment cells leads to stretching of the sensory unit and consequent opening of specific transient receptor potential vanilloid (TRPV) channels at the outer segment of the dendrite 8,12. The elicited signal is then transferred to the locomotor central pattern generator circuit in the central nervous system.
Multiple ChOs have been described in the adult fly 7. These are located near the joints of the adult fly appendages (legs, wings and halters) and in the thorax and abdomen. In addition, several hundreds of ChOs collectively form the Johnston's organ in the adult antenna that transduce acoustic to mechanical energy 3,5,17,4.
In contrast to the extensive knowledge about the development of ChOs in embryonic stages, very little is known about the morphology of these organs during larval stages. Moreover, with the exception of femoral ChOs 18 and Johnston's organ, our knowledge about the development and structure of ChOs in the adult fly is very fragmentary.
Here we describe a method for staining and visualizing ChOs in third instar larvae and pupae. This method can be applied together with genetic tools to better characterize the morphology and understand the development of the various ChOs in the fly.

Visualization of Proprioceptors in Drosophila Larvae and Pupae

A method to immunostain and visualize chordotonal organs in larvae and pupae of Drosophila melanogaster is described.

Proprioception is the ability to sense the motion, or position, of body parts by responding to stimuli arising within the body. In fruitflies and other ...

Appetitive Associative Olfactory Learning in Drosophila Larvae

In the following we describe the methodological details of appetitive associative olfactory learning in Drosophila larvae. The setup, in combination with genetic interference, provides a handle to analyze the neuronal and molecular fundamentals of specifically associative learning in a simple larval brain.
Organisms can use past experience to adjust present behavior. Such acquisition of behavioral potential can be defined as learning, and the physical bases of these potentials as memory traces1-4. Neuroscientists try to understand how these processes are organized in terms of molecular and neuronal changes in the brain by using a variety of methods in model organisms ranging from insects to vertebrates5,6. For such endeavors it is helpful to use model systems that are simple and experimentally accessible. The Drosophila larva has turned out to satisfy these demands based on the availability of robust behavioral assays, the existence of a variety of transgenic techniques and the elementary organization of the nervous system comprising only about 10,000 neurons (albeit with some concessions: cognitive limitations, few behavioral options, and richness of experience questionable)7-10.
Drosophila larvae can form associations between odors and appetitive gustatory reinforcement like sugar11-14. In a standard assay, established in the lab of B. Gerber, animals receive a two-odor reciprocal training: A first group of larvae is exposed to an odor A together with a gustatory reinforcer (sugar reward) and is subsequently exposed to an odor B without reinforcement 9. Meanwhile a second group of larvae receives reciprocal training while experiencing odor A without reinforcement and subsequently being exposed to odor B with reinforcement (sugar reward). In the following both groups are tested for their preference between the two odors. Relatively higher preferences for the rewarded odor reflect associative learning - presented as a performance index (PI). The conclusion regarding the associative nature of the performance index is compelling, because apart from the contingency between odors and tastants, other parameters, such as odor and reward exposure, passage of time and handling do not differ between the two groups9.

Appetitive Associative Olfactory Learning in Drosophila Larvae

Drosophila larvae are able to associate odor stimuli with gustatory reward. Here we describe a simple behavioral paradigm that allows the analysis of appetitive associative olfactory learning.

In the following we describe the methodological  details of appetitive associative olfactory learning in Drosophila larvae. The setup, in combination with ...

Light Preference Assay to Study Innate and Circadian Regulated Photobehavior in Drosophila Larvae

Light acts as environmental signal to control animal behavior at various levels. The Drosophila larval nervous system is used as a unique model to answer basic questions on how light information is processed and shared between rapid and circadian behaviors. Drosophila larvae display a stereotypical avoidance behavior when exposed to light. To investigate light dependent behaviors comparably simple light-dark preference tests can be applied. In vertebrates and arthropods the neural pathways involved in sensing and processing visual inputs partially overlap with those processing photic circadian information. The fascinating question of how the light sensing system and the circadian system interact to keep behavioral outputs coordinated remains largely unexplored. Drosophila is an impacting biological model to approach these questions, due to a small number of neurons in the brain and the availability of genetic tools for neuronal manipulation. The presented light-dark preference assay allows the investigation of a range of visual behaviors including circadian control of phototaxis.

Light Preference Assay to Study Innate and Circadian Regulated Photobehavior in Drosophila Larvae

Here we describe a light-dark preference test for Drosophila larva. This assay provides information about innate and circadian regulation of light sensing and processing photobehavior.

Light acts as environmental signal to control animal behavior at various levels. The Drosophila larval nervous system is used as a unique model to answer ...

Optogenetic Perturbation of Neural Activity with Laser Illumination in Semi-intact Drosophila Larvae in Motion

Drosophila larval locomotion is a splendid model system in developmental and physiological neuroscience, by virtue of the genetic accessibility of the underlying neuronal components in the circuits1-6. Application of optogenetics7,8 in the larval neural circuit allows us to manipulate neuronal activity in spatially and temporally patterned ways9-13. Typically, specimens are broadly illuminated with a mercury lamp or LED, so specificity of the target neurons is controlled by binary gene expression systems such as the Gal4-UAS system14,15. In this work, to improve the spatial resolution to "sub-genetic resolution", we locally illuminated a subset of neurons in the ventral nerve cord using lasers implemented in a conventional confocal microscope. While monitoring the motion of the body wall of the semi-intact larvae, we interactively activated or inhibited neural activity with channelrhodopsin16,17 or halorhodopsin18-20, respectively. By spatially and temporally restricted illumination of the neural tissue, we can manipulate the activity of specific neurons in the circuit at a specific phase of behavior. This method is useful for studying the relationship between the activities of a local neural assembly in the ventral nerve cord and the spatiotemporal pattern of motor output.

Optogenetic Perturbation of Neural Activity with Laser Illumination in Semi-intact Drosophila Larvae in Motion

Here we describe a protocol for optogenetic manipulation of motoneuronal activity while monitoring changes in motor output (muscle contraction) in semi-intact Drosophila larvae using lasers within a conventional confocal microscope. This technique enables researchers to achieve local perturbation of neural activity in a few neuromeres to elucidate the dynamics of motor circuits.

Drosophila larval locomotion is a splendid model system in developmental and physiological neuroscience, by virtue of the genetic accessibility of the ...

A Single-fly Assay for Foraging Behavior in Drosophila

For many animals, hunger promotes changes in the olfactory system in a manner that facilitates the search for appropriate food sources. In this video article, we describe an automated assay to measure the effect of hunger or satiety on olfactory dependent food search behavior in the adult fruit fly Drosophila melanogaster. In a light-tight box illuminated by red light that is invisible to fruit flies, a camera linked to custom data acquisition software monitors the position of six flies simultaneously. Each fly is confined to walk in individual arenas containing a food odor at the center. The testing arenas rest on a porous floor that functions to prevent odor accumulation. Latency to locate the odor source, a metric that reflects olfactory sensitivity under different physiological states, is determined by software analysis. Here, we discuss the critical mechanics of running this behavioral paradigm and cover specific issues regarding fly loading, odor contamination, assay temperature, data quality, and statistical analysis.

A Single-fly Assay for Foraging Behavior in Drosophila

In this video article, we describe an automated assay to measure the effect of hunger or satiety on olfactory dependent food search behavior in the adult fruit fly Drosophila melanogaster.

For many animals, hunger promotes changes in the olfactory system in a manner that facilitates the search for appropriate food sources. In this video ...

Straightforward Assay for Quantification of Social Avoidance in Drosophila melanogaster

Drosophila melanogaster is an emerging model to study different aspects of social interactions. For example, flies avoid areas previously occupied by stressed conspecifics due to an odorant released during stress known as the Drosophila stress odorant (dSO). Through the use of the T-maze apparatus, one can quantify the avoidance of the dSO by responder flies in a very affordable and robust assay. Conditions necessary to obtain a strong performance are presented here. A stressful experience is necessary for the flies to emit dSO, as well as enough emitter flies to cause a robust avoidance response to the presence of dSO. Genetic background, but not their group size, strongly altered the avoidance of the dSO by the responder flies. Canton-S and Elwood display a higher performance in avoiding the dSO than Oregon and Samarkand strains. This behavioral assay will allow identification of mechanisms underlying this social behavior, and the assessment of the influence of genes and environmental conditions on both emission and avoidance of the dSO. Such an assay can be included in batteries of simple diagnostic tests used to identify social deficiencies of mutants or environmental conditions of interest.

Straightforward Assay for Quantification of Social Avoidance in Drosophila melanogaster

Here, we present a protocol to quantify the avoidance of stressed individuals. This paradigm is powerful yet user-friendly and can be used to assess the influence of genes and environment on one kind of social interaction in Drosophila melanogaster.

Drosophila melanogaster is an emerging model to study different aspects of social interactions. For example, flies avoid areas previously occupied by ...

A Simple and Inexpensive Method for Determining Cold Sensitivity and Adaptation in Mice

Cold hypersensitivity is a serious clinical problem, affecting a broad subset of patients and causing significant decreases in quality of life. The cold plantar assay allows the objective and inexpensive assessment of cold sensitivity in mice, and can quantify both analgesia and hypersensitivity. Mice are acclimated on a glass plate, and a compressed dry ice pellet is held against the glass surface underneath the hindpaw. The latency to withdrawal from the cooling glass is used as a measure of cold sensitivity.
Cold sensation is also important for survival in regions with seasonal temperature shifts, and in order to maintain sensitivity animals must be able to adjust their thermal response thresholds to match the ambient temperature. The Cold Plantar Assay (CPA) also allows the study of adaptation to changes in ambient temperature by testing the cold sensitivity of mice at temperatures ranging from 30 &#176;C to 5 &#176;C. Mice are acclimated as described above, but the glass plate is cooled to the desired starting temperature using aluminum boxes (or aluminum foil packets) filled with hot water, wet ice, or dry ice. The temperature of the plate is measured at the center using a filament T-type thermocouple probe. Once the plate has reached the desired starting temperature, the animals are tested as described above.
This assay allows testing of mice at temperatures ranging from innocuous to noxious. The CPA yields unambiguous and consistent behavioral responses in uninjured mice and can be used to quantify both hypersensitivity and analgesia. This protocol describes how to use the CPA to measure cold hypersensitivity, analgesia, and adaptation in mice.

The Cold Plantar Assay (CPA) measures cold responsiveness between 30 &#176;C and 5 &#176;C, and can also measure cold adaptation. This protocol describes how to use the CPA to measure cold hypersensitivity, analgesia, and adaptation in mice.

Cold hypersensitivity is a serious clinical problem, affecting a broad subset of patients and causing significant decreases in quality of life.  The cold ...

Foraging Path-length Protocol for Drosophila melanogaster Larvae

The Drosophila melanogaster larval path-length phenotype is an established measure used to study the genetic and environmental contributions to behavioral variation. The larval path-length assay was developed to measure individual differences in foraging behavior that were later linked to the foraging gene. Larval path-length is an easily scored trait that facilitates the collection of large sample sizes, at minimal cost, for genetic screens. Here we provide a detailed description of the current protocol for the larval path-length assay first used by Sokolowski. The protocol details how to reproducibly handle test animals, perform the behavioral assay and analyze the data. An example of how the assay can be used to measure behavioral plasticity in response to environmental change, by manipulating feeding environment prior to performing the assay, is also provided. Finally, appropriate test design as well as environmental factors that can modify larval path-length such as food quality, developmental age and day effects are discussed.

Foraging Path-length Protocol for Drosophila melanogaster Larvae

We provide a detailed protocol for a Drosophila melanogaster foraging path-length assay. We discuss the preparation and handling of test animals, how to perform the assay and analyze the data.

The Drosophila melanogaster larval path-length phenotype is an established measure used to study the genetic and environmental contributions to behavioral ...

Taste Preference Assay for Adult Drosophila

Olfactory and gustatory perception of the environment is vital for animal survival. The most obvious application of these chemosenses is to be able to distinguish good food sources from potentially dangerous food sources. Gustation requires physical contact with a chemical compound which is able to signal through taste receptors that are expressed on the surface of neurons. In insects, these gustatory neurons can be located across the animal's body allowing taste to play an important role in many different behaviors. Insects typically prefer compounds containing sugars, while compounds that are considered bitter tasting are avoided. Given the basic biological importance of taste, there is intense interest in understanding the molecular mechanisms underlying this sensory modality. We describe an adult Drosophila taste assay which reflects the preference of the animals for a given tastant compound. This assay may be applied to animals of any genetic background to examine the taste preference for a desired soluble compound.

Taste Preference Assay for Adult Drosophila

Taste is an important sensory process which facilitates attraction to beneficial substances and avoidance of toxic substances. This protocol describes a simple ingestion assay for determining Drosophila gustatory preference for a given chemical compound.

Olfactory and gustatory perception of the environment is vital for animal survival.  The most obvious application of these chemosenses is to be able to ...