Early Developmental Exposure to Δ9-Tetrahydrocannabinol Causes Hyperactivity In Larval Zebrafish That Persists Into Adulthood

Due to the increasing availability of Δ9-tetrahydrocannabinol (THC), evaluation of the potential adverse behavioral effects following exposure to this cannabinoid during early development is crucial. Following exposure to 0.08, 0.4, or 1 µM THC as larvae (6-96 hours post fertilization), this study measured the latent behavioral effects caused by THC through testing the fish at the following life stages: larval photomotor response (LPR) at 120 hpf, and open field testing (OFT) at 3 weeks post fertilization (juvenile), 11 wpf (onset of sexual maturity) and 24 wpf (adulthood). During the LPR test, hyperactivity in the dark phase was evident in larval zebrafish exposed to 0.4 µM THC. Further, open field tests were conducted at 3 and 11 wpf where dose-dependent hyperactivity and increased thigmotaxis were apparent across the two highest concentrations of THC-exposed zebrafish. Adult zebrafish were also tested 6 months post fertilization. The OFT revealed a significant difference in terms of behavior between male and females as well as significant increases in velocity amongst fish exposed to 0.4 or 1 µM THC of both sexes. These results suggest that exposure to THC during critical periods of development can cause behavioral alterations that persist in zebrafish into adulthood