Zebrafish Larva’s Response and Habituation to Electric Signal: Effects
of Voltage, Current and Pulsation Studied in a Microfluidic Device
Abstract
We previously showed that electric current can cause zebrafish larvae to
move towards the anode pole along a microchannel. For a semi-mobile
larva, we observed that zebrafish response to electricity depended on
the current magnitude. The effects of electric signal direction, voltage
magnitude and habituation to repeated exposures to electric pulses were
not characterized. Here, this knowledge gap was addressed by exploiting
these parameters in a microfluidic device with a head-trap to immobilize
a zebrafish larva and a downstream chamber for tail movement and
phenotypic characterization of response duration (RD) and tail beat
frequency (TBF). We first assessed larvae’s response to electric current
direction (at 3µA) and voltage magnitude. Changing the current direction
significantly altered the RD and TBF with long and low-frequency
responses seen when the anode was positioned at larvae’s tail. The
electric voltage drop across the fish body had a significant effect on
larvae’s locomotion with long RD and low TBF observed at 5.6V in the
range of 1.3-9V. We also demonstrated that the zebrafish locomotor
response to repeated 3µA current pulses diminished with dependency on
the interstimulus interval. However, the diminished response was fully
recovered after a 5-min resting period or introduction of a novel light
stimulus (i.e. habituation-dishabituation strategy). Therefore, electric
response suppression in zebrafish was attributed to the habituation as a
form of non-associative learning. Our microfluidic platform has broad
application potential in behavioral neuroscience to study cognitive
phenotypes, fundamental studies on the biological roots of electric
response, and pharmacological screening.