A Microfluidic System for Stable and Continuous EEG Monitoring from Multiple Larval Zebrafish

Abstract

Along with the increasing popularity of larval zebrafish as an experimental animal in the fields of drug screening, neuroscience, genetics, and developmental biology, the need for tools to deal with multiple larvae has emerged. Microfluidic channels have been employed to handle multiple larvae simultaneously, even for sensing electroencephalogram (EEG). In this study, we developed a microfluidic chip capable of uniform and continuous drug infusion across all microfluidic channels during EEG recording. Owing to the modular design of the microfluidic channels, the number of animals under investigation can be easily increased. Using the optimized design of the microfluidic chip, liquids could be exchanged uniformly across all channels without physically affecting the larvae contained in the channels, which assured a stable environment maintained all the time during EEG recording, by eliminating environmental artifacts and leaving only biological effects to be seen. To demonstrate the usefulness of the developed system in drug screening, we continuously measured EEG from four larvae without and with pentylenetetrazole application, up to 60 min. In addition, we recorded EEG from valproic acid (VPA)-treated zebrafish and demonstrated the suppression of seizure by VPA. The developed microfluidic system could contribute to the mass screening of EEG for drug development to treat neurological disorders such as epilepsy in a short time, owing to its handy size, cheap fabrication cost, and the guaranteed uniform drug infusion across all channels with no environmentally induced artifacts.

Modelling epilepsy in the mouse: challenges and solutions

“…Seizures can be elicited using convulsants such as PTZ or kainic acid, or by genetic manipulation, and typically involve hyperactive swimming followed by loss of posture ( Afrikanova et al, 2013 ; Baraban et al, 2013 ). Electrographic seizures can be detected using EEG, which has been developed for use in both larval ( Lee et al, 2020 ) and adult ( Cho et al, 2017 ) forms. Seizure activity can also be directly visualised in the transparent larvae using transgenic reporters ( Burrows et al, 2020 ).…”

THE ZEBRAFISH ANIMAL MODEL (Danio rerio) USED FOR DIFFERENT THERAPEUTIC APPROACHES FOR THE SUPPRESSION OF EPILEPTIC CRISIS: A SYSTEMATIC REVIEW

“…There are also studies that have established that the zebrafish brain regions show functions homologous to their mammalian counterparts, despite important neuroanatomical differences (9)(10)(11)(13)(14)(15)(16)(17)(19)(20)(21)24,27,28,42,43).…”

“…The microfluidic EEG system that can detect EEG of several larvae simultaneously, creating a microfluidic chip to hold the larva in a stable way and change the liquid uniformly in all channels (9).…”

“…Through the branch-shaped microfluidic channels, the liquid could be filled uniformly with the same gradient along the channels, even with the larvae contained within it (9).…”

“…Brains of more complex mammals and organisms for the purposes of genetic modeling, including zebrafish, have been widely studied and zebrafish has gained great popularity in behavioral neuroscience and research in psychopharmacology (9) In addition, the zebrafish model system offers large-scale screening and resembles the complexity of the central nervous system (CNS) (10). Interestingly, the genetic compositions of zebrafish are comparable to humans with 70% genetic similarity, while 84% of the genes known for human diseases are widely expressed in zebrafish (11).…”