This protocol is an excerpt from Tong et al, <a href="https://www.jove.com/video/50226/microfluidic-based-electrotaxis-for-on-demand-quantitative-analysis">Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of Caenorhabditis elegans&#39; Locomotion</a>, J. Vis. Exp. (2013).
1. Electrotaxis Experiment
<ol>
	<li>Place the microchannel on the stage (preferably XY-movable) of a microscope with a mounted camera connected to a monitor (Figure 1).</li>
	<li>Connect the power supply or amplifier&#39;s output wires to the microchannel&#39;s electrodes. A simple DC power supply is sufficient if only a DC signal is desired, but an amplifier connected to a function generator allows application of pulsed DC and AC signals as well.</li>
	<li>Attach the microchannel&#39;s output tube to a disposable syringe. Submerge the mouth of the inlet tube in M9 physiological buffer and gently aspire liquid into the channel by applying a negative pressure inside the syringe (either manually or using a syringe pump). When the inlet and outlet tubes are both filled with M9, disconnect the syringe from the tube. Level both tubes to the same height to prevent hydrostatically driven flow.</li>
	<li>Apply a DC voltage to the channel and ensure that resistance (R= V/I) is around 0.6 M&#937; (for a 50 mm long, 0.3 mm wide and ~0.1 mm deep microchannel).</li>
	<li>If satisfied with the channel&#39;s integrity, follow the above steps to load worms from a diluted suspension into the channel.</li>
	<li>Disconnect the syringe and hydrostatically manipulate the flow by adjusting the tubes&#39; relative height. Use this method to place a worm in the center of the channel and then lay both tubes flat at the same elevation.</li>
	<li>Set the power supply to the appropriate voltage: 4-12 V/cm for L3 stage animals, 4-10 V/cm for L4s, and 2-4 V/cm for young adults. Activate the electric signal and allow 1 min of pre-exposure for the worm to acclimatize to the field. The worm should begin moving towards the cathode. When the minute has passed, use the camera to begin recording.</li>
	<li>For AC and pulsed DC experiments, the maximum responsive electric field can be adopted from above and frequency and duty cycle of the signal can be modulated as desired.</li>
	<li>When experiment is finished, remove all liquid (and worms) from the channel, rinse it with dH20, and leave the device on a hot plate at 125 &#176;C to dry.</li>
	<li>Extract locomotory data from recorded videos manually using NIH ImageJ (<a href="http://rsbweb.nih.gov/ij/" target="_blank">http://rsbweb.nih.gov/ij/</a>) or custom MATLAB-based worm tracking software.</li>
</ol>

electrotaxis assay: a method to observe locomotion in c. elegans

Electrotaxis Assay: A Method to Observe Locomotion in C. elegans

Source: Tong, J, et al. <a href="https://www.jove.com/video/50226/microfluidic-based-electrotaxis-for-on-demand-quantitative-analysis">Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of Caenorhabditis elegans&#39; Locomotion.</a> J. Vis. Exp. (2013).
Researchers can trigger on-demand movement in C. elegans by applying an electric field that worms sense and respond to. This video introduces electrotactic behavior and shows a sample protocol that is done in a microfluidic device.

<img alt="Microfluidics setup diagram with CCD camera, power supplies, syringe pump, inverted microscope." src="/files/ftp_upload/20162/20162fig1.jpg" data-altupdatedat="1753371239000" data-alt="Figure 1" /> 
Figure 1. Schematic of microfluidic screening platform for nematode electrotaxis assay.

Source: Tong, J,&#160;et al. Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of&#160;Caenorhabditis elegans&#39; Locomotion.&#160;J. ...

- Without sensory stimuli, C. elegans movement is generally forward and is interrupted by reversals and turns-- random reorienting maneuvers that result in a change of direction. C. elegans are electroreceptive. That is, they can sense electric fields. When exposed to a mild direct current or DC, worms move in a straight uninterrupted path in the direction of the negative electrode or cathode, a behavior termed electrotaxis. To more accurately observe the worm's locomotion, place the animal in a microfluidic device and apply a DC electric field. Reverse the direction of the field, and the worm will turn the opposite way-- towards the direction of the cathode. Apply an alternating current, AC, and the worm will stop. The alternating change in the field's direction overwhelms the worm's neuromotor systems, resulting in the worm's immobilization. Reapply the DC field, and the worm will resume forward motion towards the cathode. In the following example protocol, we will see a setup demonstrating an electrotaxis assay in a microfluidic device. - Begin this step by placing the just assembled micro-channel onto an xy- movable stage of a microscope with a mounted camera connected to a monitor. Connect the power supply to the micro-channel's electrodes. After confirming that the resistance of the micro-channel is around 0.6 mega-ohms, attach the output tube of the micro-channel to a disposable syringe. Then submerge the mouth of the inlet tube into a solution of nematodes suspended in M9 physiological buffer. Apply negative pressure inside the syringe to aspirate liquid into the channel. When the inlet and outlet tubes are both filled, disconnect the syringe and hydro-statically manipulate the flow by adjusting the tube's relative height to place a worm in the center of the channel. Then lay both tubes flat at the same elevation. To maintain zero flow inside the micro-channel when switching worm samples during an electrotaxis experiment, after leveling both the inlet tubes to the same elevation, if there is still flow make small adjustments to the tube's height relative to each other. - If we are ever unsure of whether the flow is really zero, we can induce a reversal in the worm's movement by changing the polarity of the electric field and then evaluating the worm's linear velocity as it turns around. - Now, set the power supply to the appropriate voltage. Activate the electric signal, and allow one minute of pre-exposure for the worm to acclimatize to the field, during which time the worm should begin moving towards the cathode. When the minute has passed, begin recording. When the experiment is finished, remove all the liquid and worms from the channel. Rinse the chamber with de-ionized water and leave the device on a hot plate at 125 degrees Celsius to dry.

electrotaxis-assay-a-method-to-observe-locomotion-in-c-elegans

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Caenorhabditis elegans (worm)

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2.1K Views. - Without sensory stimuli, C. elegans movement is generally forward and is interrupted by reversals and turn...

Electrotaxis Assay: A Method to Observe Locomotion in C. elegans

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Protocol

<img title="figure-results-1" alt="Microfluidics setup diagram with CCD camera, power supplies, syringe pump, inverted microscope." src="/files/ftp_upload/20162/20162fig1.jpg" data-altupdatedat="1753371239000" data-alt="Figure 1" /> 
Figure 1. Schematic of microfluidic screening platform for nematode electrotaxis assay.

Electrotaxis Assay: A Method to Observe Locomotion in C. elegans

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