Understanding the impacts of antipsychotic pharmaceuticals on behaviour in fish

With the increasing global population, expanded market access, advances in pharmaceuticals, and broadening therapeutic applications, active pharmaceutical ingredients (APIs) are increasingly detected in environmental matrices. APIs enter the environment predominantly via treated and untreated wastewater sources, resulting in persistent and widespread exposure as they disperse through ecosystems; yet the ecological implications of their presence in the environment remain poorly understood. Among these APIs, neuroactive pharmaceuticals, and particularly antipsychotic drugs (APDs), represent an emerging environmental concern due to their pseudo-presence, bioaccumulative potential and potency in modulating central nervous system (CNS) targets. APDs act on evolutionarily conserved monoaminergic, adrenergic, histaminergic, and muscarinic receptors expressed in neural and peripheral tissues across taxa. Despite these risks, APDs remain understudied compared to other neuroactive pharmaceutical classes (e.g. antidepressants), with their ecological implications on complex biological systems and food webs, largely unknown. Behavioural endpoints have emerged as particularly sensitive measures for assessing effects of neuroactive agents, hence the development of the field of behavioural ecotoxicology. Behavioural sensitivity is thought to serve as an ‘early warning sign’ of underlying physiological changes which may not manifest acutely. Nevertheless, if environmental responsiveness is altered at sublethal levels through behaviour (e.g. leading to inappropriate reactions to environmental cues) a significant risk to fitness can manifest. Behavioural ecotoxicology is especially pertinent for APDs which are known to induce a range of on-target and often severe and involuntary off-target (including extrapyramidal symptoms) behavioural effects. This thesis explores the risks posed by APDs through behavioural assessments in zebrafish (Danio rerio), covering diverse compounds from all three generations of APDs. Across the life stages covered here (embryos, larvae, and adults), APDs produced compound- and concentration- specific behavioural signatures at several fitness-related endpoints, including tail coiling, touch response, locomotion, feeding, and aversion, suggesting plausible ecological consequences for exposed fish. Broad screenings identified clear differences in developmental toxicity, with quetiapine emerging as the compound of greatest concern, exhibiting the lowest sublethal no-observed-effect concentration (NOEC), one order of magnitude below its lethal threshold (NOEC). Liquid chromatography-tandem mass spectrometry also confirmed bioavailability of all tested compounds to the developing embryos. These initial findings additionally highlighted the value of refined sensitive behavioural screening tools for detecting subtle neuroactive effects that may be otherwise overlooked in conventional fish embryo testing. More sophisticated light-dark locomotor paradigms revealed illumination-dependent behavioural signatures that were partially mirrored by neural activity patterns measured using fluorescence light-sheet microscopy. Compounds that did not significantly alter neural activity, such as haloperidol, produced minimal locomotor disruption, whereas agents inducing robust activity and connectivity changes exhibited correspondingly stronger behavioural phenotypes, supporting some predictive validity of the imaging readouts. Fluorescence-based neural activity further distinguished pharmacological classes, with older typical APDs having a more limited global impact, in contrast to newer atypical APDs which generated broader, concentration-dependent neural profiles. Among these atypicals, quetiapine, risperidone and aripiprazole produced the most extensive changes across key regions of interest. These agents were later assessed on the attraction-aversion axis, finding reliable changes to feeding behaviour, including a reduction in feeding efficiency for quetiapine. Following these high-coverage assessments and subsequent analyses, the focus was narrowed to detailed investigations of one agent (quetiapine) at environmentally realistic concentrations, providing novel insights into the uptake and chronic exposure dynamics of this compound, although behavioural effects were not detected within the risk-balancing phenotype under these conditions. Effects within this thesis were primarily found at concentrations several orders of magnitude above typical environmental detections (in surface or effluent water); however, environmentally relevant margins were narrowed for more targeted analysis. Significant behavioural responses in feeding assays occured at concentrations overlapping those reported for quetiapine (2 – 20× the highest measured environmental concentration [MEC]) and approaching the upper range of risperidone MEC (10× that measured in surface water), suggesting that localised exposure hotspots may present a specific ecological risk. Collectively, the results underscore important considerations for environmental risk assessment, emphasizing compound-specific, concentration-dependent, and life stage-sensitive risks. The research acknowledges further complexities of real-world environments that include environmental stressors, mixtures and transgenerational impacts, which whilst outside the scope of this thesis, could interact with APDs to enhance the effects found here, and ultimately emphasising the growing importance of addressing these factors as global APD prescriptions continue to rise.<p></p>

Author dc:creator

• Gaby Wasser (21040784)

• antipsychotic
• zebrafish
• behaviour
• pharmaceuticals

Statement dc:rights

• All rights reserved
• Open Access after 2030-05-25

Identifier

10779/exe.32400207.v1

OAI identifier oai:identifier

oai:figshare.com:article/32400207