Browsing by Author "Gelderblom, Michelle"

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    Understanding the effect of protocol variations in the zebrafish light/dark transition test
    (Stellenbosch : Stellenbosch University, 2023-03) Gelderblom, Michelle; Smith, Carine; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Dept. of Medicine. Division of Clinical Pharmacology.
    ENGLISH ABSTRACT: Anxiety disorders have devastating individual and societal costs, and are a major contributor to years lost to disability worldwide. They appear to be increasing in prevalence, both in South Africa and the world at large. Although there are medications to treat anxiety, there is a need for more treatment options. Anxiety is often not treated effectively due to treatment resistance or non-compliance to medication due to side effects. One of the best options for identifying novel anxiolytics is to use animal models. Zebrafish are useful for screening of potential anxiolytic treatments because they are the most well-studied vertebrate model that shares the size, cost and fecundity benefits of invertebrate models. The light/dark transition test (LDTT) is the most widely used zebrafish larvae behavioural test. It has many applications in pharmacology, particularly in toxicology and screening for potential pharmaceuticals, including treatments for anxiety disorders. It is likely to be one of the first tests used when screening for neuroactivity in zebrafish larvae. During the test, zebrafish larvae are exposed to a period of light followed by an abrupt transition to darkness which produces a hyperlocomotion response that responds to anxiolytics and anxiogenics. The design of the LDTT varies between studies, but it is unclear how common protocol variations affect the comparison of results and contextualisation of data generated using slightly varied protocols. Through both prospective experiments and retrospective data analysis, the effect of age (from 2 dpf to 5 dpf), lighting conditions during rearing (standard or continuous darkness), capture order, repeated light/dark cycles, repeated light/dark transition tests, duration of the light period (1 minute or 10 minutes), light intensity during the light period, and breeding stocks on the response to the light/dark transition test was measured. All experiments consisted of an acclimation period, and at least one cycle consisting of a light period and a dark period. Experiments were recorded using the DanioVision system and activity was measured automatically using the EthoVision XT software. Variations in age, time of day, light period and breeding stock had a significant impact on the response to the light/dark transition test and should therefore be carefully controlled. Light conditions during rearing did not have a statistically significant effect, but more research is needed to confirm that variations in light-rearing do not affect response to the light/dark transition test. Finally, capture order, repeated cycles, repeated light/dark transition tests and light/dark transition intensity did not have a significant effect, suggesting that they can vary according to logistical requirements without affecting results. This opens up the use of repeated measurements that facilitate identifying neuroactivity when the amount of time it will take for the onset of action is unknown. This informs both experimental design, and which studies are comparable. It will also facilitate the use of the light/dark transition test to screen for potential anxiolytics.