Assessment of Larval Zebrafish Locomotor Activity for Developmental Neurotoxicity Screening

Zebrafish Larvae Rapidly Recover from Locomotor Effects and Neuromuscular Alterations Induced by Cholinergic Insecticides

“…It is currently challenging to identify chemicals with the potential to interfere with the developing nervous system because rodent-based test strategies, such as the OECD test guideline 426, are time- and resource-intensive, unspecific, and ethically challenging. , In light of the high number of chemicals with neurotoxic potential that remain untested, − there is currently an urgent need for new developmental neurotoxicity (DNT) test strategies involving alternative methods . While for human DNT testing, 3D neuronal/glial microphysiological systems are on the verge of being developed as standard methods, , zebrafish behavioral assays are currently the focus of both eco-neurotoxicological , and human DNT test strategies. , One test, which is commonly applied by many laboratories, is the zebrafish light–dark transition (LDT) test . It measures the larvae’s locomotor reactions to light changes, which are characterized by low activity during light phases, a rapid activity increase upon transition to complete darkness, and high activity during darkness.…”

“…16 While for human DNT testing, 3D neuronal/glial microphysiological systems are on the verge of being developed as standard methods, 17,18 zebrafish behavioral assays are currently the focus of both eco-neurotoxicological 19,20 and human DNT test strategies. 21,22 One test, which is commonly applied by many laboratories, is the zebrafish light−dark transition (LDT) test. 23 It measures the larvae's locomotor reactions to light changes, which are characterized by low activity during light phases, a rapid activity increase upon transition to complete darkness, and high activity during darkness.…”

Developmental Neurotoxicity and Behavioral Screening in Larval Zebrafish with a Comparison to Other Published Results

“…Moreover, our definition of normal appears to be stricter than some other laboratories: not only did the larva need to present without malformations, but the swim bladder had to be inflated. If the animal appeared normal with an uninflated swim bladder, that animal was not included in the behavioral analysis, as it is known that a zebrafish larva with an uninflated swim bladder does not behave normally in some assays [ 69 , 70 ]. In fact, if they do not inflate their swim bladder by 9 dpf, there is a high likelihood the larva will die [ 81 ].…”

“…We are assuming that any changes in swimming activity during the behavioral assessment is due to nervous system function and not changes in physical locomotor ability precipitated by teratological changes. To accomplish this, each animal was carefully assessed for any morphological changes, including swim bladder inflation as swim bladder inflation status has been shown to affect behavioral endpoints [ 69 , 70 ].…”

“…Morphological assessments focused on the following: craniofacial (abnormal eyes or head), spinal (stunted, curved, or kinked tail), abdominal region (edema or emaciation), thoracic region (distention or heart malformations), swim bladder inflation, and position in the water column (floating or lying on side). All dead, unhatched, malformed larvae, and those with uninflated swim bladders, were eliminated from any behavioral analysis; malformed 6 dpf zebrafish larvae, as well as normal appearing larvae with uninflated swim bladders, do not behave normally in our behavioral paradigm [ 65 , 69 ]. Following the assessments, larvae were anaesthetized using cold shock and then euthanized with 20% ( v / v ) bleach solution.…”