We would like to thank Chris Wreden and Michelle Bland for comments on the manuscript and for technical help.

1. Preparation of Larvae
<ol>
	<li>One week before recording behavior, set up a cross (minimum of 25 virgins and 5 males). Maintain all crosses and progeny at 25 &#176;C. 
	NOTE: The temperature of culture conditions can be altered, but the time line described below would need to be adjusted to account for changes in developmental speed.</li>
	<li>5 days before recording, first thing in the morning, place the cross into a collection cage with an agar/juice cap and a dab (0.5-1 ml) of yeast paste in the center of t...

<ol>
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The authors have nothing to disclose.

A microfluidic device was built to make linear agarose channels that can accommodate Drosophila larvae (Figure 1). When Drosophila larvae are placed in these linear agarose channels their behavioral repertoire is limited to crawling, which allows for detailed observation of the dynamics of larval structures over the crawl cycle.
A successful recording occurs when a larva perform a series of rhythmic strides (Figure 3). If this does not occur,...

The overall goal of this method is to study Drosophila larval crawling in detail. Experiments on locomotion have played an important role in developing and testing theories on motor control2. Traditionally locomotion has been studied in aquatic animals (e.g., leech, lamprey, tadpole)3. The repetitive nature of locomotion in these animals has allowed for the study of rhythmogenesis, for analysis of the biophysical events driving locomotion, and for monitoring the neural firing patterns that accompany locomotion.
The use of Drosophila larvae for studies of locomotion presents a unique combination of advantages over other model systems: facile genetics, well-characterized development, a body that is optically clear at first and second instars, and an ongoing transmission electron microscopic reconstruction of the entire nervous system4-6. However, Drosophila larval locomotion on flat open surfaces is somewhat complex including pauses, turns, and meandering crawls7. This publication presents a method to use linear agarose channels to guide Drosophila larval locomotor behavior such that larvae perform sustained, straight, rhythmic crawling behavior.
Studying Drosophila larval behavior in agarose channels, instead of behavior on flat open surfaces, has several advantages. First, it allows researchers to specifically select crawling behavior from the many movements that are part of the larval behavioral repertoire. Second, by adjusting the width of the channel versus the larval body size, crawling speed can be adjusted. Third, channels allow for the larva to be viewed from dorsal, ventral, or lateral side depending on how the larva is loaded and oriented within the channel. This versatility in larval orientation allows for any structure of interest to be continually visible during crawling. Fourth, channels are amenable for use with a wide variety of microscopes and objectives. For example, linear channels can be used for low-resolution imaging on bright-field stereoscopes and/or for high-resolution imaging on spinning-disc confocal microscopes1. Fifth, this method can be used in combination with optogenetic/thermogenetic neuronal manipulations in any genetic background. Finally, because both the larval body (at first and second instars) and agarose channels are optically clear, channels can be used when studying the dynamic movements, or changes in fluorescent intensity of larval structures labeled by genetically-encoded fluorescent probes.
The method described is appropriate for detailed kinematic studies of first and second instar Drosophila larval behavior. This publication analyzes the dynamic changes in fluorescent intensity of the CNS during forward larval crawling to demonstrate the use of channels and as a precursor to neuronal calcium imaging.

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		<tr height="21">
			<td height="21" style="height:21px;width:211px;">6 oz square Drosophila bottle</td>
			<td style="width:101px;">Scimart</td>
			<td style="width:119px;">DR-103</td>
			<td style="width:212px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">agar</td>
			<td style="width:101px;">sigma</td>
			<td style="width:119px;">A1296</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">sucrose</td>
			<td style="width:101px;">sigma</td>
			<td style="width:119px;">S9378</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">apple juice</td>
			<td></td>
			<td></td>
			<td>not from concentrate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Tegosept</td>
			<td>Fisher</td>
			<td>T2300</td>
			<td>methyl-p-hydroxybenzoate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">35 x 10 mm round petri dish</td>
			<td style="width:101px;">Fisher</td>
			<td align="right">351008</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">baker&#39;s yeast</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">PDMS casting mold</td>
			<td style="width:101px;">FlowJem</td>
			<td style="width:119px;"></td>
			<td>can be requested from authors</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">isopropyl alcohol</td>
			<td style="width:101px;">Fisher</td>
			<td style="width:119px;">A417-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">laboratory wipes</td>
			<td style="width:101px;">Fisher</td>
			<td style="width:119px;">06-666-11</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">canned air</td>
			<td style="width:101px;">Fisher</td>
			<td style="width:119px;">18-431</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">10 cm petri dish</td>
			<td style="width:101px;">BioPioneer</td>
			<td style="width:119px;">GS82-1473-001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">agarose</td>
			<td style="width:101px;">Fisher</td>
			<td style="width:119px;">50-444-176</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">razor blade</td>
			<td style="width:101px;">Fisher</td>
			<td style="width:119px;">12-640</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">forceps</td>
			<td style="width:101px;">FST</td>
			<td style="width:119px;">11241-40</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">22 x 40 cover glass, #1.5</td>
			<td style="width:101px;">Fisher</td>
			<td style="width:119px;">50-365-605</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Fiji (version 1.51d)</td>
			<td style="width:101px;">NIH</td>
			<td style="width:119px;"></td>
			<td>fiji.sc</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">Excel 2016</td>
			<td style="width:101px;">Microsoft</td>
			<td></td>
			<td>www.microsoftstore.com</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:211px;">MATLAB R2016</td>
			<td style="width:101px;">Mathworks</td>
			<td style="width:119px;"></td>
			<td>www.mathworks.com</td>
		</tr>
	</tbody>
</table>

using linear agarose channels to study drosophila larval crawling behavior

Drosophila larval crawling is emerging as a powerful model to study neural control of sensorimotor behavior. However, larval crawling behavior on flat open surfaces is complex,&#160;including: pausing, turning, and meandering. This complexity in the repertoire of movement hinders detailed analysis of the events occurring during a single crawl stride cycle. To overcome this obstacle, linear agarose channels were made that constrain larval behavior to straight, sustained, rhythmic crawling. In principle, because agarose channels and the Drosophila larval body are both optically clear, the movement of larval structures labeled by genetically-encoded fluorescent probes can be monitored in intact, freely-moving larvae. In the past, larvae were placed in linear channels and crawling at the level of whole organism, segment, and muscle were analyzed1. In the future, larvae crawling in channels can be used for calcium imaging to monitor neuronal activity. Moreover, these methods can be used with larvae of any genotype and with any researcher-designed channel. Thus the protocol presented below is widely applicable for studies using the Drosophila larva as a model to understand motor control.

This article describes a method for guiding Drosophila larval behavior using agarose channels and for measuring the dynamics of larval structures over a crawl cycle. Larvae in linear channels perform sustained bouts of rhythmic crawling (Figure 3). Because both larvae and channels are optically clear, channels can be used with larvae expressing fluorescent probes expressed in any structure of interest. We recorded larvae expressing GFP in all neurons (elav-Ga...

Watch this Scientific Journal Video about Using Linear Agarose Channels to Study Drosophila Larval Crawling Behavior at JoVE.com

Using Linear Agarose Channels to Study Drosophila Larval Crawling Behavior

The Drosophila larva is a powerful model system to study neural control of behavior. This publication describes the use of linear agarose channels to elicit sustained bouts of linear crawling and methods to quantify the dynamics of larval structures during repetitive crawling behavior.

Using Linear Agarose Channels to Study Drosophila Larval Crawling Behavior

Drosophila larval crawling is emerging as a powerful model to study neural control of sensorimotor behavior. However, larval crawling behavior on flat ...

The overall goal of this procedure is to observe larval stage Drosophila crawling in a linear agarose channel to study the development of neural circuits. This method can help answer key questions in the fields of neuro ethology and developmental biology, such as understanding the neural codes that generate motor patterns and identifying key genetic and cellular processes that scope neuronal circuits for movement control. The main advantage of this technique is that it restricts the larval behavior repertoire so that the researchers can study a single multi pattern in detail.Demonstrating the procedure will be Zarion Marshall a technician from my laboratory. First it is important to assess the larva's health. Three to four days before recording, replace the collection plate of the adult cage.Proceed to do this daily and at the same time of day. Count the eggs and newly hatched larvae on the plate. The expected number of eggs is between 500 and 2, 000.Adjust the number of adults in the cage as needed. We examine the plate 24 hours later to determine whether the larvae are healthy. Most of the eggs should have hatched into larvae, and the larvae should have crawled into the yeast paste.Signs of poor health include a large number of unhatched eggs, dead larval bodies away from the yeast paste, and larvae with unusually dark patches in the abdomen which is an indicator of an immune reaction. If the larvae appear unhealthy, change the cage using freshly prepared plates, and check the adults genotype. For the experiment collect newly hatched second instar larvae from one to two day old plates.All these stages can be used in the analysis. For this protocol, have a linear channel PDMS casting mold. Clean the casting mold with isopropyl alcohol.Once it is dried, place the mold into a ten centimeter lid or similar container. Then fill the mold with three percent agarose cooled to 55 degrees Celsius. Pour the agarose carefully to avoid trapping air bubbles in the mold.The mold should be just covered by the agarose. Once solidified, remove the agarose channels from the mold. Trim the edges of the disc shaped channels, and then immerse the channels in water.They can be stored in water at four degrees Celsius for up to seven days. Before using the channels, allow them to warm to room temperature. Select a channel that matches the width of the larva.The channels range from 100 to 300 microns in width and are all 150 microns deep. Then use a clean razor blade to cut a single channel from the prepared disc. With forceps transfer the channel to an appropriately sized glass cover slip or slide with the grooved side up.Next, use fine forceps to gently pick up a larva without squeezing it. A finely tipped paintbrush also works well. If squeezed, pain reflexes such as rolling or hunching may dominate the larva's behavior in the channel.Now wash the larva by briefly submerging it in water, and then place it into the cut channel gently teasing it into position. Once in the channel, adjust the orientation of the larva to make the structure of interest easy to image. Then place one or two drops of water at either end of the channel to fill the channel with water.If any air bubbles get trapped, gently lift the sides of the channel to remove them. To further adjust the orientation of the larva, gently nudge the channel to roll the larva around. The larva is now ready to be imaged.Larvae in linear channels perform sustained bouts of rhythmic crawling. Fluorescent probes are easily examined. For example, larvae expressing GFP in their neurons from the GAL4 driver show dynamic changes in fluorescent intensities emanating from the nerve cord during the crawl cycle.The CNS moves forward at nearly the same time as the larval head and tail as a wave of muscle contraction passes along the body axis, the CNS moves in and out of the plane of focus, causing the fluorescence of the nerve cord to change. The changes in fluorescence were quantified from three crawl strides for three larvae. The dynamics of the nerve cord fluorescence over the stride cycle followed a reproduce able pattern that could be used for phenotyping.After watching this video, you should have an understanding of how to collect larvae for behavior, to prepare agarose channels, and to load the larvae into the channels to visualize the linear crawling behavior. While attempting this procedure, it is important to remember to handle the larvae gently.

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7.2K 조회수.  University of Chicago. The overall goal of this procedure is to observe larval stage Drosophila crawling in a linear agarose channel to study the development of neural circuits. This method can help answer key questions in the fields of neuro ethology and developmental biology, such as understanding the neural codes that generate motor patterns and identifying key genetic and cellular processes that scope neuronal circuits for movement control. The main advantage of this technique is that it restricts the larval be...