Major depressive disorder (MDD) remains a leading cause of global morbidity and mortality, and many patients do not respond to existing treatments. The authors investigated whether the volume-regulated anion channel (VRAC) contributes to depression- and anxiety-related molecular and behavioural phenotypes, using zebrafish as an experimental model. VRAC requires the LRRC8A subunit for function; the zebrafish ortholog of this obligatory subunit is lrrc8aa.
The study manipulated VRAC function through two primary strategies described by the authors. First, VRAC was pharmacologically inhibited (details of the inhibitors and concentrations were reported in the original article). Second, the team used morpholino-mediated knockdown of lrrc8aa to reduce VRAC function genetically. Behavioural assays were performed in zebrafish larvae to assess anxiety- and depression-like phenotypes, and transcriptomic analysis was carried out on lrrc8aa-deficient larvae to identify molecular pathway changes. In adult zebrafish, the investigators applied a chronic unpredictable stress paradigm and tested pharmacological modulation of VRAC in that context.
Both approaches that reduced VRAC function—pharmacological inhibition and morpholino-mediated knockdown of lrrc8aa—produced behavioural phenotypes interpreted as anxiety-like and depression-like in zebrafish larvae. In addition to behavioural changes, VRAC disruption altered expression of genes previously associated with affective disorders. The authors interpret these findings as evidence that diminished VRAC activity can contribute to behavioural features relevant to human mood disorders.
The report includes transcriptomic profiling of larvae deficient in lrrc8aa. This analysis revealed dysregulation of pathways implicated in neuronal signalling and in cellular stress responses. According to the authors, these molecular changes provide mechanistic context linking reduced VRAC function to altered neural signalling and to stress-related cellular processes that are relevant to affective disorder biology.
The authors tested pharmacological activation of VRAC using zinc pyrithione (ZPT). Administration of ZPT improved the behavioural abnormalities observed after VRAC disruption and partially restored gene expression changes in larvae. These findings are presented by the authors as evidence that boosting VRAC activity can reverse both behavioural and some molecular consequences of VRAC loss.
In adult zebrafish exposed to a chronic unpredictable stress protocol, treatment with ZPT produced antidepressant- and anxiolytic-like effects that the authors report were comparable to those produced by the tricyclic antidepressant imipramine. ZPT treatment also normalized elevated expression of monoamine oxidase (mao) observed in stressed adult fish. The authors therefore propose that pharmacological activation of VRAC can modulate stress-related behavioural and molecular endpoints in adult animals as well as in larvae.
Taken together, the findings reported by the authors indicate that reduced VRAC function contributes to depression- and anxiety-related behavioural and molecular phenotypes in zebrafish and identify VRAC as a potential target for the development of novel antidepressant therapies. The study integrates behavioural, genetic, pharmacological, and transcriptomic data to support this conclusion.
It is important to note that this work is presented as a preprint on bioRxiv and has not been peer reviewed; the authors also declared no competing interests. The research was supported by the Indian Council of Medical Research. Specific experimental details, such as exact pharmacological agents, dosages, behavioural assay parameters, and full transcriptomic datasets, are reported in the original manuscript and supplementary material linked in the source. Where those specific methodological details are not restated here, they were not reported in the summary source used for this rewrite.
This preclinical study supports a model in which diminished activity of VRAC—mediated by loss of the LRRC8A ortholog lrrc8aa or by pharmacological inhibition—can produce both molecular signatures and behavioural changes relevant to anxiety and depression in zebrafish. Conversely, pharmacological activation of VRAC with zinc pyrithione (ZPT) reversed behavioural abnormalities, partially restored gene-expression changes, and produced effects in stressed adult fish comparable to imipramine, including normalization of mao expression. The authors propose VRAC as a candidate target for future antidepressant development, while noting that the findings are preclinical and presented in a non–peer-reviewed preprint.