Brewing Anxiety: Caffeine-Induced Thigmotaxis in Zebrafish Larvae.

BACKGROUND

Thigmotaxis, or edge preference, is widely used as a measure of anxiety in vertebrate model systems. However, variability in this behavior limits its utility as a scalable measure for anxiolytic drug discovery. In the current study, we examine caffeine-induced thigmotaxis, using 5-day-old zebrafish larvae as a model system.

METHOD: We modified our imaging system and AI-assisted analysis for measurements of behavior in six-well plates. The imaging system was used to measure thigmotaxis and several other behaviors, including overall activity, scoot and burst swimming, and responses to acoustic and visual stimuli.

RESULT: Caffeine (100 mg/L) caused the zebrafish larvae to exhibit increased edge preference, decreased activity, increased scooting, and decreased bursting behavior. Coadministration with diazepam (0.25 mg/L), a central nervous system depressant, significantly reduced caffeine-induced thigmotaxis and increased locomotor activity.

CONCLUSION

These findings support edge preference as a reliable measure of anxiety and reconcile existing conflicting results regarding diazepam's anxiolytic efficacy in zebrafish larvae, suggesting that anxiolytic effects are most pronounced against a heightened anxiety baseline. These findings also establish a robust platform for high-throughput identification of anxiolytic compounds with potential relevance for treating anxiety and related stress in humans.