Tail Coiling Assay in Zebrafish (Danio rerio) Embryos: Stage of Development, Promising Positive Control Candidates, and Selection of an Appropriate Organic Solvent for Screening of Developmental Neurotoxicity (DNT)

Andréia De Oliveira,Tamires Brigante,Danielle Oliveira

doi:10.3390/w13020119

Abstract

It is relatively recent that tail coiling assay in zebrafish (Danio rerio) embryos has been proposed as an alternative method to screen for developmental neurotoxicity (DNT) induced by chemicals. Despite the considerable use of the method, there is no consensus related to the most suitable age of embryos and other experimental parameters. Non-exposed embryos were videotaped for tail-coiling activity from 18 to 54 h post-fertilization (hpf) and after exposure to positive control candidates (caffeine, fluoxetine, and tricaine (MS-222)) and organic solvents (acetone, dimethyl-sulfoxide (DMSO), and ethanol) from 26.0 to 28.5 hpf. Results demonstrated that embryos from 22 to 29 hpf presented a constant coiling activity, with no significant differences between the activity measurements. We also found that stimulant properties of caffeine and the anesthetic effects of MS-222 induced hyperactivity and hypoactivity, respectively. Finally, even using DMSO at 1%, it seems to be safer as a solvent for neurotoxicity evaluation by tail coiling assay. The period from 26.0 to 28.5 hpf was appropriate for a fast protocol of tail coiling assay. Caffeine and MS-222 were demonstrated to be promising positive control candidates, whereas DMSO was considered the most appropriate solvent choice for tail coiling assay.

Highlights

It is well-known that the developing nervous system presents higher sensitivity to some chemical exposure when compared to the adult nervous system
When we shortened the period between measurements and monitored the coiling activity from to 30 hpf every 1 h, results demonstrated that there were no significant differences between measurements from burst activity, mean burst duration, or burst counts per minute (Figure 3a–c)
We reported tail coiling activity through the percentage of time spent in activity (“burst activity”), and the percentage of time the embryo was immobile (“inactivity”), which was useful for monitoring the hypoactivity

Summary

Introduction

It is well-known that the developing nervous system presents higher sensitivity to some chemical exposure when compared to the adult nervous system. This fact occurs because normal development of the nervous system commonly requires spatial and temporal coordination of critical events, such as proliferation, migration, differentiation, synaptogenesis, myelination, and apoptosis, that can be impaired by toxicants [1,2]. The large number of animals, long duration of tests, and intensive use of resources have been raising criticism and drawing attention to the need for more realistic test protocols for regulatory purposes, especially in terms of cost-effectiveness [6,7,8]

Methods

Results

Discussion

Conclusion