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 a medium-sized, clean petri dish (60 mm x 15 mm).</li>
	<li>Next, gently sort larvae by size using forceps or a paintbrush to preclude larger &#34;wandering 3rd instar&#34; or small sickly larvae from being tested. Discard larvae containing any undesired genetic markers or balancers.</li>
	<li>Have a fellow lab member label dishes or containers where sorted larvae will be placed so that the experimenter can be &#34;blind&#34; to the experimental condition or genotype of the larvae if applicable. The experimenter can apply decoded labels to collected data after the experiment using a key generated by a lab-member.</li>
	<li>Using a scoopula, transfer a dime-sized amount of fresh food into a (35 mm x 10 mm or 60 mm x 15 mm) clean, labeled Petri dish filled half-way with room temperature water.</li>
	<li>Gently move the sorted larvae onto the food (to prevent starvation or desiccation if testing is anticipated to take more than 20 min) using forceps or paintbrush.</li>
</ol>
2. Cold Probe Assay
<ol>
	<li>Turn on the cold probe unit allowing a few min for it to cool to the desired temperature. If setting to lower temperatures, condensation will likely form along the probe.</li>
	<li>Wipe away any excess moisture with a laboratory wipe before application to the larva. When not in immediate use, place insulating cap on probe to both insulate and to keep the tip clean and prevent damage.</li>
	<li>Place a mid 3rd instar larva onto a thin piece of dark moveable vinyl (typically, use a small piece cut from a notebook binder) under a bright field microscope. The black vinyl aids in contrast visualization and in moving the larva without touching it to align it properly with the probe.</li>
	<li>Adjust the microscope (see Table of Materials) and light unit (see Table of Materials) to medium brightness (50-75% max brightness) to provide contrast and prevent the larva from drying out too quickly.</li>
	<li>Discard any larvae that do not first exhibit normal peristaltic locomotion as they&#160;could confound the results. The larva should be moist from the Petri dish of water otherwise the larva will stick to the vinyl inhibiting normal locomotion. Water should not puddle around the larva.</li>
	<li>Advance the probe by hand towards the larva at a 90&#186; angle to the anteroposterior body axis, using the vinyl to move the larva into correct position (see Figure 1A).</li>
	<li>Orient the tip of the probe to gently lay across the mid dorsal surface of the larva with the probe at approximately a 45&#186; angle to the microscope stage.</li>
	<li>Upon probe contact, start a laboratory timer. Apply enough downward pressure to slightly indent the surface of the larval cuticle while still allowing forward or backward movement.</li>
	<li>Hold the probe in place for up to 10 s&#160;or until a cold-evoked behavioral response is observed - whichever occurs first. Then remove the probe.</li>
	<li>Record the observed behavioral response and the response latency. Larvae that do not respond within 10 s&#160;are considered &#34;non-responders&#34;. Latency can also be recorded for responders and used to measure changes in response robustness/amplitude.</li>
	<li>Discard larva and prepare the next.</li>
	<li>Repeat steps 2.3-2.11 until the desired number of test larvae is reached (three sets of n = 20-40 larvae were used here).</li>
</ol>

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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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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. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+Maggots+Move+-+Allometry+and+Kinematics+of+Crawling+in+Larval+Diptera.">How Maggots Move - Allometry and Kinematics of Crawling in Larval Diptera.</a> J. Insect Physiol. 41 (4), 329-337 (1995).</li><li>Galko, M. J., Krasnow, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+and+genetic+analysis+of+wound+healing+in+Drosophila+larvae.">Cellular and genetic analysis of wound healing in Drosophila larvae.</a> PLoS Biol. 2 (8), E239 (2004).</li><li>Burra, S., Wang, Y., Brock, A. R., Galko, M. 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A United States patent application (CL) is pending on the design of the cold probe. Additional information on details of cold probe part numbers and construction, as well as additional consulting on tool design will be provided upon request.

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><tbody><tr><td>Cold Probe</td><td>Pro-Dev Engineering</td><td>Custom-built on demand</td><td>Part numbers and construction details can be provided on request</td></tr><tr><td>Thermal Control Unit</td><td>TE Technology</td><td>Custom Built enclosure</td><td>Part numbers and construction details can be provided on request</td></tr><tr><td>Zeiss Stemi 2000 microscope</td><td>Zeiss</td><td>NT55-605</td><td></td></tr><tr><td>Fiber-Lite MI-150 High Intensity Illuminator</td><td>Dolan-Jenner Industries.</td><td>A20500</td><td></td></tr><tr><td>Schott Dual Gooseneck 23 inch Fiber Optic Light Guide</td><td>Schott North America, Inc.</td><td>Schott A08575</td><td></td></tr><tr><td>Forceps</td><td>FST</td><td>FS-1670</td><td>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><td>Paintbrush</td><td>Dick Blick Art Materials</td><td>06762-1002</td><td>Used to sort and handle larvae. It is helpful if the paintbrush is damp during use.</td></tr><tr><td>35 mm x 10 mm Polystyrene Petri dish</td><td>Falcon</td><td>351008</td><td></td></tr><tr><td>60mm x 10 mm Polystyrene Petri dish</td><td>Falcon</td><td>351007</td><td></td></tr><tr><td>Piece of black vinyl (at least 2 inches x 2 inches)</td><td></td><td></td><td>Used to provide contrast and orient larvae to the cold probe</td></tr><tr><td>Fisherbrand Scoopula Spatula</td><td>Fisher Scientific</td><td>14-357Q</td><td>Used to move food</td></tr><tr><td>Kimtech Science Kimwipes</td><td>Fisher Scientific</td><td>06-666A</td><td>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 ...

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

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7.7K Views.  UT MD Anderson Cancer Center. 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.

Video: Novel Assay for Cold Nociception in Drosophila Larvae

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 ...

Novel Whole-tissue Quantitative Assay of Nitric Oxide Levels in Drosophila Neuroinflammatory Response

Neuroinflammation is a complex innate immune response vital to the healthy function of the central nervous system (CNS). Under normal conditions, an intricate network of inducers, detectors, and activators rapidly responds to neuron damage, infection or other immune infractions. This inflammation of immune cells is intimately associated with the pathology of neurodegenerative disorders, such as Parkinson&#39;s disease (PD), Alzheimer&#39;s disease and ALS. Under compromised disease states, chronic inflammation, intended to minimize neuron damage, may lead to an over-excitation of the immune cells, ultimately resulting in the exacerbation of disease progression. For example, loss of dopaminergic neurons in the midbrain, a hallmark of PD, is accelerated by the excessive activation of the inflammatory response. Though the cause of PD is largely unknown, exposure to environmental toxins has been implicated in the onset of sporadic cases. The herbicide paraquat, for example, has been shown to induce Parkinsonian-like pathology in several animal models, including Drosophila melanogaster. Here, we have used the conserved innate immune response in Drosophila to develop an assay capable of detecting varying levels of nitric oxide, a cell-signaling molecule critical to the activation of the inflammatory response cascade and targeted neuron death. Using paraquat-induced neuronal damage, we assess the impact of these immune insults on neuroinflammatory stimulation through the use of a novel, quantitative assay. Whole brains are fully extracted from flies either exposed to neurotoxins or of genotypes that elevate susceptibility to neurodegeneration then incubated in cell-culture media. Then, using the principles of the Griess reagent reaction, we are able to detect minor changes in the secretion of nitric oxide into cell-culture media, essentially creating a primary live-tissue model in a simple procedure. The utility of this model is amplified by the robust genetic and molecular complexity of Drosophila melanogaster, and this assay can be modified to be applicable to other Drosophila tissues or even other small, whole-organism inflammation models.

Novel Whole-tissue Quantitative Assay of Nitric Oxide Levels in Drosophila Neuroinflammatory Response

Levels of the inflammatory cell-signaling molecule nitric oxide (NO) are commonly assayed using Griess reagent. In this protocol, we have created a modified Griess assay utilizing live Drosophila brain tissue in order to detect the secretion of NO in a simple, quantifiable and highly repeatable method.

Neuroinflammation is a complex innate immune response vital to the healthy function of the central nervous system (CNS). Under normal conditions, an ...

Immunology and Infection

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 ...

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 ...

An Improved Assay and Tools for Measuring Mechanical Nociception in Drosophila Larvae

Published assays for mechanical nociception in Drosophila have led to variable assessments of behavior. Here, we fabricated, for use with Drosophila larvae, customized metal nickel-titanium alloy (nitinol) filaments. These mechanical probes are similar to the von Frey filaments used in vertebrates to measure mechanical nociception. Here, we demonstrate how to make and calibrate these mechanical probes and how to generate a full behavioral dose-response from subthreshold (innocuous or non-noxious range) to suprathreshold (low to high noxious range) stimuli. To demonstrate the utility of the probes, we investigated tissue damage-induced hypersensitivity in Drosophila larvae. Mechanical allodynia (hypersensitivity to a normally innocuous mechanical stimulus) and hyperalgesia (exaggerated responsiveness to a noxious mechanical stimulus) have not yet been established in Drosophila larvae. Using mechanical probes that are normally innocuous or probes that typically elicit an aversive behavior, we found that Drosophila larvae develop mechanical hypersensitization (both allodynia and hyperalgesia) after tissue damage. Thus, the mechanical probes and assay that we illustrate here will likely be important tools to dissect the fundamental molecular/genetic mechanisms of mechanical hypersensitivity.

An Improved Assay and Tools for Measuring Mechanical Nociception in Drosophila Larvae

The goal of this protocol is to show how to perform an improved assay for mechanical nociception in Drosophila larvae. We use the assay here to demonstrate that mechanical hypersensitivity (allodynia and hyperalgesia) exists in Drosophila larvae.

Published assays for mechanical nociception in Drosophila have led to variable assessments of behavior. Here, we fabricated, for use with Drosophila ...

Behavior

A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae

Many animals, including the fruit fly, Drosophila melanogaster, are capable of discriminating minute differences in&#160;environmental temperature, which enables them to seek out their preferred thermal landscape. To define the temperature preferences of larvae over a defined linear range, we developed an assay using a temperature gradient. To establish a single-directional gradient, two aluminum blocks are connected to independent water baths, each of which controls the temperature of individual blocks. The two blocks set the lower and upper limits of the gradient. The temperature gradient is established by placing an agarose-coated aluminum plate over the two water-controlled blocks so that the plate spans the distance between them. The ends of the aluminum plate that is set on the top of the water blocks defines the minimum and maximum temperatures, and the regions in-between the two blocks form a linear temperature gradient. The gradient assay can be applied to&#160;larvae of different ages and can be used to identify mutants that exhibit phenotypes, such as those with mutations affecting genes encoding TRP channels and opsins, which are required for temperature discrimination.

A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae

Here, we present a protocol to determine the preferred environmental temperature of Drosophila larvae using a continuous thermal gradient.

Many animals, including the fruit fly, Drosophila melanogaster, are capable of discriminating minute differences in&#160;environmental temperature, which ...

Behavioral Assays for Optogenetic Manipulation of Neural Circuits in Drosophila melanogaster

Optogenetics has become a fundamental technique in neuroscience, enabling precise control of neuronal activity through light stimulation. This study introduces easy-to-implement setups for applying optogenetic methods in Drosophila melanogaster. Two optogenetic tools, CsChrimson, a red-light-activated cation channel, and GtACR2, a blue-light-activated anion channel, were employed in four experimental approaches. Three of these approaches involve single-fly experiments: (1) a blue-light optogenetic thermotactic positional preference assay targeting temperature-sensitive heating cells, (2) a red-light optogenetic positional preference assay activating bitter sensing neurons, and (3) a proboscis extension response assay activating the sweet-sensing neurons. The fourth approach (4) is a fly maze setup to assess avoidance behaviors using multiple flies. The ability to manipulate neural activity temporally and spatially offers powerful insights into sensory processing and decision-making, underscoring the potential of optogenetics to advance our knowledge of neural function. These methods provide an accessible and robust framework for future research in neuroscience to enhance the understanding of specific neural pathways and their behavioral outcomes.

This paper presents methods for optogenetic manipulation in Drosophila melanogaster, utilizing CsChrimson and GtACR2 to activate and silence specific neurons. Four experiments are described to utilize optogenetics to explore thermotactic and gustatory behaviors, providing insights into the underlying neural mechanisms governing these processes.

Optogenetics has become a fundamental technique in neuroscience, enabling precise control of neuronal activity through light stimulation. This study ...

Local Heat Probe Assay: A Method to Assess Nociception of High Temperatures in Drosophila Larvae

Source: Chattopadhyay, A., et al. <a href="https://www-jove-com.remotexs.ntu.edu.sg/video/3837/" target="_blank">Local and Global Methods of Assessing Thermal Nociception in Drosophila Larvae</a>. J. Vis. Exp. (2012).
Drosophila larvae have dedicated sensory neurons&#8211;nociceptors&#8211;whose response to potentially harmful thermal stimuli triggers aversive&#8211;or so-called &#34;nocifensive&#34;&#8211;behaviors in the animal. This video describes a method to assess thermal nociception by recording larval behavior in response to local application of a heat probe onto the cuticle. This method is, therefore, called the local heat probe assay.

Source: Chattopadhyay, A., et al. Local and Global Methods of Assessing Thermal Nociception in Drosophila Larvae. J. Vis. Exp. (2012).
Drosophila larvae ...

Novel Assay for Cold Nociception in Drosophila Larvae

Summary

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Local and Global Methods of Assessing Thermal Nociception in Drosophila Larvae

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Novel Whole-tissue Quantitative Assay of Nitric Oxide Levels in Drosophila Neuroinflammatory Response

Appetitive Associative Olfactory Learning in Drosophila Larvae

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

A Single-fly Assay for Foraging Behavior in Drosophila

An Improved Assay and Tools for Measuring Mechanical Nociception in Drosophila Larvae

A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae

Behavioral Assays for Optogenetic Manipulation of Neural Circuits in Drosophila melanogaster

Local Heat Probe Assay: A Method to Assess Nociception of High Temperatures in Drosophila Larvae