Effect of pulse direct current signals on electrotactic movement of nematodes Caenorhabditis elegans and Caenorhabditis briggsae

Abstract

The nematodes (worms) Caenorhabditiselegans and Caenorhabditisbriggsae are well-known model organisms to study the basis of animal development and behaviour. Their sinusoidal pattern of movement is highly stereotypic and serves as a tool to monitor defects in neurons and muscles that control movement. Until recently, a simple yet robust method to initiate movement response on-demand did not exist. We have found that the electrical stimulation in a microfluidic channel, using constant DC electric field, induces movement (termed electrotaxis) that is instantaneous, precise, sensitive, and fully penetrant. We have further characterized this behaviour and, in this paper, demonstrate that electrotaxis can also be induced using a pulse DC electric signal. Worms responded to pulse DC signals with as low as 30% duty cycle by moving towards the negative electrode at the same speed as constant DC fields (average speed of C. elegans = 296 ± 43 μm/s and C. briggsae = 356 ± 20 μm/s, for both constant and pulse DC electric fields with various frequencies). C. briggsae was found to be more sensitive to electric signals compared to C. elegans. We also investigated the turning response of worms to a change in the direction of constant and pulse DC signals. The response for constant DC signal was found to be instantaneous and similar for most worms. However, in the case of pulse DC signal, alterations in duty cycle affected the turning response time as well as the number of responding worms. Our findings show that pulse DC method allows quantitative measurement of response behaviour of worms and suggest that it could be used as a tool to study the neuronal basis of such a behaviour that is not observed under constant DC conditions.

Electrotaxis of oral squamous cell carcinoma cells in a multiple-electric-field chip with uniform flow field

“…1,2 Many different cell types and organisms show electrotactic response to dcEF, including neural stem cell, 3 induced pluripotent stem cells, 4 mesenchymal stem cells, 5,6 fibroblasts, [7][8][9] keratinocytes, 10,11 neurons, 2 and C. elegans. 12,13 The physiological dcEF with strength of tens to hundreds of mV per mm (mVÁmm À1 ) originates from the difference in transepithelial potential (TEP), which is supposedly formed by the differential distribution of ion channels on polarized epithelial cells. 1, 14 In recent years, many groups have reported that cancer cells also show electrotactic behavior.…”

Galvanotaxis of Caenorhabditis elegans: current understanding and its application in improving research

“…Worms exhibited normal life cycle, reproductive behavior and locomotion post-exposure to EF and upon post-paralysis events [34]. Rezai et al (2011) developed a microfluidic device to study the electro-sensation behavior of the worms (C. elegans and C. briggsae) (Figure 3) and showed that the worms response not only to constant DC electric field but also to pulse DC electric field [35].…”

Recent Developments in Electrotaxis Assays

“…Electrotaxis of C. elegans has been studied in direct current, alternating current, or pulse EF. [21][22][23] Research using C. elegans often requires sorting worms by their stages or separating normal worms and mutants. Besides various existing sorting methods, electrotaxis provides a simple and effective way to sort C. elegans.…”