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Browsing by Author "Hagen, Ethan V."

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    Exploring the impact of acute solvent exposure on larval zebrafish behaviour
    (2025) Hagen, Ethan V.; Harper, Matthew M. M.; Zhang, Yanbo; Hamilton, Trevor
    Zebrafish (Danio rerio) are commonly used to test the impact of pharmacological and toxicological compounds. Larval zebrafish are extensively used because of high throughput procedures allowing simultaneous behavioural measurement in 24-, 48-, or 96-well plates. Often solvents are used as a vehicle for poorly soluble or insoluble compounds, however, the impact of dimethyl sulfoxide (DMSO), methanol, and ethanol after acute administration is not well characterized. Here we investigated the impact of 30-min exposures of DMSO, methanol, and ethanol (0.01%, 0.1%, and 1.0% vol/vol) on 5-day old larval zebrafish locomotion and startle responses. We found no effect of DMSO on distance moved and thigmotaxis in a spontaneous swimming test, and no effect on dark-, light-, or tap-startle responses compared to controls. Methanol and ethanol, both at 1.0% increased the distance moved, and ethanol decreased the dark startle response at 1.0%. Neither ethanol nor methanol had any impact on time in thigmotaxis zone, light- or tap-startle responses. Results from this study suggest that with acute exposure to experimental compounds requiring a solvent, the least impact on behaviour would occur with DMSO, followed by methanol, then ethanol.
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    From colours to cravings: exploring conditioned colour preference to ethanol in zebrafish
    (2025) Hagen, Ethan V.; Zhang, Yanbo; Hamilton, Trevor
    Conditioned preference paradigms like conditioned colour preference tests (CCP) can be used to investigate addictive drug seeking in zebrafish (Danio rerio), but many aspects of this procedure require further study. Conditioned preference can be tested with either biased or unbiased conditioning methods, each with their own strengths and weaknesses. The present study used unbiased stimuli to test seeking behaviour in ethanol-exposed zebrafish at different durations of drug withdrawal. Zebrafish were exposed to one of two equally preferred colours (red or yellow) while dosed with 0.8 % vol/vol ethanol or with habitat water (controls) for 1 h each day for 21 days. Next, fish experienced withdrawal for either 2-, 4-, or 8-days then were tested in a two-way red and yellow task for 10 min with their movement recorded via motion-tracking software. Fish conditioned to red showed a main effect of ethanol and a significant preference for red compared to yellow at 8-days of withdrawal but not at 2-days or 4-days of withdrawal. Fish conditioned to yellow did not show any colour preference during the 2-, 4-, or 8-days of withdrawal, but did show a main effect of withdrawal duration. This work expands our understanding of CCP paradigms in zebrafish and highlights the capacity of zebrafish to develop an association to red but not yellow under our experimental conditions.
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    Innate colour preference in zebrafish (Danio rerio)
    (2023) Hagen, Ethan V.; Zhang, Yunhui; Hamilton, Trevor
    Innate (natural) colour preference in animals is used for a variety of behavioural neuroscience purposes in many animal models. In zebrafish, colour preference is often used in combination with place preference testing and some memory tests. However, baseline colour preference seems to differ in the few studies examining this innate behaviour. This necessitates a protocol for reliable colour preference testing to establish preferences prior to using more complex behavioural paradigms. This procedure involves an aquatic plus maze with a central neutral zone and 4 coloured zones: red, green, yellow, blue. Adult zebrafish spent significantly more time in the blue zone compared to the red and yellow zones. There were no sex differences in colour preference. This procedure is a rapid, affordable, straightforward, and effective method to establish baseline colour preference.
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    Plating larval zebrafish prior to the day of experimentation has no impact on spontaneous swimming and startle responses
    (2025) Harper, Matthew M. M.; Hagen, Ethan V.; Zhang, Yanbo; Hamilton, Trevor
    Behavioural testing in larval zebrafish often involves pipetting the larvae into well plates for individual testing. Transferring larvae into plates the day prior to experimentation can increase efficiency of testing. Furthermore, pharmacological and toxicological studies can require a prolonged dosing period requiring the larvae to be pre-plated into the well plate the day prior to experimentation. Here, we compared the behavioural impact of pre-plating larval zebrafish at 4 days post-fertilization (dpf) to fish transferred at 5 dpf on the day of testing. Motion-tracking software was used to examine locomotion and zone preference, and responses to light, dark, and mechanical startle stimuli. We found no significant differences in distance moved, time spent in the thigmotaxis zone (outside edge of the arena), high mobility, immobility, light startle, dark startle, and mechanical startle responses. This data suggests that pre-plating larval zebrafish one day prior to testing does not have a significant impact on behaviour in a spontaneous swim task, dark startle test, light startle test, or mechanical startle test. Pre-plating larval zebrafish can increase the efficiency of behavioural testing. • Compare plating larvae one day prior to testing to plating day of testing. • Test the behaviour in a spontaneous swimming test, and measure light-, dark-, and mechanical-startle responses. • There were no significant differences in locomotion or startle responses.
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    Repeated microdoses of LSD do not alter anxiety or boldness in zebrafish
    (2024) Hagen, Ethan V.; Schalomon, Melike; Zhang, Yunhui; Hamilton, Trevor
    The therapeutic use of lysergic acid diethylamide (LSD) has resurfaced in the last decade, prompting further scientific investigation into its effectiveness in many animal models. Zebrafish (Danio rerio) are a popular model organism in medical sciences and are used to examine the repeated administration of pharmacological compounds. Previous zebrafish research found acute LSD altered behaviour and cortisol levels at high (250 µg/L) but not low (5–100 µg/L) levels. In this study, we used a motion tracking system to record and analyze the movement patterns of zebrafish after acute and repeated 10-day LSD exposure (1.5 µg/L, 15 µg/L, 150 µg/L) and after seven days of withdrawal. The open-field and novel object approach tests were used to examine anxiety-like behaviour, boldness, and locomotion. In the acute experiments we observed a significant decrease in high mobility with 1.5 µg/L, 15 µg/L, and 150 µg/L of LSD compared to the control and a decrease in velocity with 1.5 and 15 µg/L. In repeated experiments, there were no significant differences in the levels of anxiety, boldness, or locomotion between all LSD groups and controls immediately after 10-day treatment or after withdrawal.