Simple mazes have provided numerous tasks for assessing working memory. The discrete nature of choices in the T-maze has provided a robust protocol with sensitivity to cognitive deficits, whilst the continuous Y-maze reduces manual handling and pre-trial training. We have combined these attributes to develop a new behavioural task for assessing working memory, the Free-movement pattern (FMP) Y-maze. Using sequentially recorded left and right turns we demonstrate that zebrafish and mice use a single dominant strategy predominantly consisting of alternations between left and right choices trial-to-trial. We further tested this protocol with Drosophila and discovered an alternative invertebrate search strategy. Finally, a virtual human FMP Y-maze confirmed a common strategy among all tested vertebrate species, validating the translational power of the task for human research. The FMP Y-maze combines robust investigation of working memory and high translational power, generating a simple task with far-reaching impact.

Numerous neurodegenerative and psychiatric disorders are associated with deficits in executive functions such as working memory and cognitive flexibility. Progress in developing effective treatments for disorders may benefit from targeting these cognitive impairments, the success of which is predicated on the development of animal models with validated behavioural assays. Zebrafish offer a promising model for studying complex brain disorders, but tasks assessing executive function are lacking. The Free-movement pattern (FMP) Y-maze combines aspects of the common Y-maze assay, which exploits the inherent motivation of an organism to explore an unknown environment, with analysis based on a series of sequential two-choice discriminations. We validate the task as a measure of working memory and executive function by comparing task performance parameters in adult zebrafish treated with a range of glutamatergic, cholinergic and dopaminergic drugs known to impair working memory and cognitive flexibility. We demonstrate the cross-species validity of the task by assessing performance parameters in adapted versions of the task for mice and Drosophila , and finally a virtual version in humans, and identify remarkable commonalities between vertebrate species’ navigation of the maze. Together, our results demonstrate that the FMP Y-maze is a sensitive assay for assessing working memory and cognitive flexibility across species from invertebrates to humans, providing a simple and widely applicable behavioural assay with exceptional translational relevance.

When exposed to ethanol, Drosophila melanogaster display a variety of addiction-like behaviours similar to those observed in mammals. Sensitivity to ethanol can be quantified by measuring the time at which 50% of the flies are sedated by ethanol exposure (ST50); an increase of ST50 following multiple ethanol exposures is widely interpreted as development of tolerance to ethanol. Sensitivity and tolerance to ethanol were measured after administration of the gamma-aminobutyric acid receptor B (GABAB ) agonist (SKF 97541) and antagonist (CGP 54626), when compared with flies treated with ethanol alone. Dose-dependent increases and decreases in sensitivity to ethanol were observed for both the agonist and antagonist respectively. Tolerance was recorded in the presence of GABAB drugs, but the rate of tolerance development was increased by SKF 97451 and unaltered in presence of CGP 54626. This indicates that the GABAB receptor contributes to both the sensitivity to ethanol and mechanisms by which tolerance develops. The data also reinforce the usefulness of Drosophila as a model for identifying the molecular components of addictive behaviours and for testing drugs that could potentially be used for the treatment of alcohol use disorder (AUD).

Ethanol is a psychoactive substance causing both short- and long-term behavioural changes in humans and animal models. We have used the fruit fly Drosophila melanogaster to investigate the effect of ethanol exposure on the expression of the Gαq protein subunit. Repetitive exposure to ethanol causes a reduction in sensitivity (tolerance) to ethanol, which we have measured as the time for 50% of a set of flies to become sedated after exposure to ethanol (ST50). We demonstrate that the same treatment that induces an increase in ST50 over consecutive days (tolerance) also causes a decrease in Gαq protein subunit expression at both the messenger RNA and protein level. To identify whether there may be a causal relationship between these two outcomes, we have developed strains of flies in which Gαq messenger RNA expression is suppressed in a time- and tissue-specific manner. In these flies, the sensitivity to ethanol and the development of tolerance are altered. This work further supports the value of Drosophila as a model to dissect the molecular mechanisms of the behavioural response to alcohol and identifies G proteins as potentially important regulatory targets for alcohol use disorders.

Aims: Ethanol induced behaviours are mediated via the GABA-B receptor, but mechanisms remain unclear. Drosophila melanogaster respond to alcohol by developing addiction-like behaviours such as changes to ethanol sensitivity (tolerance). The aim of this study was to determine the effect of GABA-B receptor drugs on the development of alcohol tolerance in male adult Drosophila to further elucidate the role of GABA-B receptors. Methods: The GABA-B receptor agonist (SKF-97451) and antagonist (CGP-54626) were administered orally for 24h before a three-day assay to challenge ethanol tolerance in wild type and GABA-B receptor mutant flies. ST50, defined as 50% of flies sedated from ethanol exposure, was used as a measure of sensitivity on each day. Results are n=6 with 10 flies per assay. Results: Both agonist and antagonist increased the ST50 in WT and GABA-B R1 KO when compared to control. Notably, the GABA-B R2 KO did not respond to either agonist or antagonist and differed significantly from the R1 KO and WT response suggesting a complex mechanism of action. Conclusion: The data provides evidence that the GABA-B receptors are involved in modulating the process of ethanol tolerance in Drosophila melanogaster. Further work with different mutant flies and drug delivery protocols will probe the role of these receptors in alcohol addiction.

Alcohol is one of the most widely used and socially accepted psychoactive substances in the world, and its misuse was accountable for 3.3 million alcohol related deaths in the world in 2015. Whilst it is known that ethanol enhances the actions of the GABA-B receptor, the role of the stimulation of this receptor in inducing acute and chronic effects, remains to be investigated and identified. The fruit fly, Drosophila melanogaster, offers the possibility to investigate behaviours such as preference and tolerance to alcohol, and to challenge them with pharmacological agents. In this study, the GABA-B receptor agonist (SKF 97451) and antagonist (CGP 54626) were used to challenge the development of tolerance and the onset of preference to alcohol in wild type flies and in mutant lines with putative disruptions of GABAB receptor 1 or 2 subunit genes. The results indicate that the GABA-B receptors are indeed part of a complex mechanism that result in alcohol induced behavioural changes. The data support the usefulness of the Drosophila model and the need for further investigations.