Differential Electrographic Signatures Generated by Mechanistically-Diverse Seizurogenic Compounds in the Larval Zebrafish Brain

Abstract

We assessed similarities and differences in the electrographic signatures of local field potentials evoked by different pharmacological agents in zebrafish larvae. We then compared and contrasted these characteristics with what is known from electrophysiological studies of seizures and epilepsy in mammals, including humans. Ultimately, our aim was to phenotype neurophysiological features of drug-induced seizures in larval zebrafish for expanding knowledge on the translational potential of this valuable alternative to mammalian models. Local field potentials were recorded from the midbrain of 4-day old zebrafish larvae exposed to a pharmacologically diverse panel of seizurogenic compounds, and the outputs of these recordings were assessed using frequency domain analysis. This included analysis of changes occurring within various spectral frequency bands of relevance to mammalian CNS circuit pathophysiology. From these analyses, there were clear differences in the frequency spectra of drug-exposed local field potentials, relative to controls, many of which shared notable similarities with the signatures exhibited by mammalian CNS circuits. These similarities included the presence of specific frequency components comparable to those observed in mammalian studies of seizures and epilepsy. Collectively, the data presented provide important information to support the value of larval zebrafish as an alternative model for the study of seizures and epilepsy.These data also provide further insight into the electrophysiological characteristics of seizures generated in non-mammalian species by the action of neuroactive drugs. Significance StatementIn this study we offer novel insight into the frequency domain of the local field potentials (LFPs) for a range of seizurogenic compounds in zebrafish larvae. We make a direct comparison of seizurogenic compounds with varying mechanisms of action and, where possible, compare the effects of these compounds in zebrafish larvae with those recorded in mammals in terms of the frequency components of their LFPs. This study adds to the mounting body of evidence supporting the use of the larval zebrafish as a powerful alternative model organism for seizure and epilepsy research.

Establishment of innovative ZebVortrack behavioral analysis system for quantitative epileptic seizure assessment in larval zebrafish

“…Pinion induced seizures in 4dpf zebra sh using different pro-convulsants and recorded their EEG. The local eld potentials (LFP) of the larval zebra sh were similar to the characteristics exhibited by the mammalian central nervous system 7 . In addition, pro-convulsant agents can cause behavioral disorders of zebra sh, such as unstable swimming, hyperactivity, loss of posture, and the overexcitation of neurons 10 .…”

“…Danio rerio, is an emerging model animal with a small size, easy reproduction, transparent embryos, and a short growth cycle 4 , and it is easier to raise than standard experimental animals. The following features make zebra sh a useful model in the study of seizures as well as to conduct highthroughput drug screening 5,6 , such as access to local eld potential (LFP) recordings 7 , in vivo brain imaging via activity-dependent bioluminescent/ uorescent reporters 8 , the ever-expanding genetic toolbox 9 . A past research reported that larval zebra sh treated with pro-convulsant agents develop seizure-like behavior in three main stages 10 : stage I is characterized by increased swimming speed, stage II by fast swirly swimming, and stage III by the loss of body balance and rollover.…”

Zebrafish as an Innovative Tool for Epilepsy Modeling: State of the Art and Potential Future Directions

“…In particular, the monitoring of the local field potential in ZF brains has been widely performed to investigate the possible electrographic effects or changes in ZF treated with different drugs and convulsants [31,63,82,88,119]. Even if these kinds of measurements are extensively employed in ZF, the precise electrographic characteristics of electrographic seizures in these organisms after treatment with different compounds/drugs are little known [120]. These electrographic measurements are often applied to larvae.…”

“…Zebrafish larvae between 3 and 7 dpf are usually embedded in 1.2-2% low-melting-point agarose prepared in an embryo medium. One or two glass microelectrodes filled with NaCl (2 M) or with artificial cerebrospinal fluid (124 mM NaCl, 10 mM glucose, 2 mM KCl, 2 mM MgSO 4 , 2 mM CaCl 2 , 1.25 mM KH 2 PO 4 , and 26 mM NaHCO 3 NaCl) are inserted through the epidermis, into the intracranial space, into the midbrain or optic tectum or forebrain [31,63,77,78,82,87,88,91,92,[119][120][121][122][123][124]. Then, the larvae are usually treated with different doses of chemicals/drugs, and the activity is measured for 10-30 min and the obtained seizure events are compared to one of the control samples (untreated larvae).…”

“…During the development, the monitoring of seizure characteristics was poorly evaluated even with electrographic recordings coupled with a reduction of neuronal cell proliferation [49,51]. One study investigated both the impact of different concentrations of KA on the motor activity of ZF in the early stages and the impact of the pretreatment with KA in juvenile animals [120]. ZF treated with KA exhibited different behavior depending on the stage of development analyzed.…”