The Influence of Tetrahydrocannabinol (THC) on anxiety-like behavior in zebrafish larvae: A light-dark assay study

Cannabis is a commonly used illicit substance, often consumed for its potential to promote relaxation and alleviate anxiety. This study employed the light-dark transition test to examine the effects of acute delta-9-tetrahydrocannabinol (THC) exposure on anxiety-like behavior in larval zebrafish. At 7 days post-fertilization, zebrafish larvae were exposed to one of several treatments: egg water (control), 1% dimethyl sulfoxide (DMSO, vehicle control), 100 mg/L caffeine in egg water, 10 mg/L alprazolam in DMSO, and 0.01 and 0.1 mg/L THC in DMSO for 2 hours. Their behavior was then recorded during alternating light and dark periods to measure the distance traveled in each condition. Both egg water and DMSO controls demonstrated significantly higher activity levels in the dark compared to the light (p = 0.003 and 0.011, respectively). THC exposure exhibited a biphasic effect in the dark period relative to the DMSO control: lower concentrations of THC (0.01 mg/L) increased distance traveled, whereas higher concentrations (0.1 mg/L) decreased it, though these effects were not statistically significant. Additionally, larvae exposed to 0.01 mg/L THC showed higher locomotion in both light and dark periods compared to those exposed to alprazolam, but this difference was not significant. These findings suggest that THC has both anxiolytic and anxiogenic effects in the light-dark transition assay, aligning with some existing research on THC's impact on anxiety. Further studies are needed to draw more definitive conclusions, but this research provides valuable insights into THC's effects on anxiety-like behavior.