Inhibiting the endocannabinoid degrading enzymes FAAH and MAGL during zebrafish embryogenesis alters sensorimotor function.

The endocannabinoid system (eCS) plays a critical role in a variety of homeostatic and developmental processes. Although the eCS is known to be involved in motor and sensory function, the role of endocannabinoid (eCB) signaling in sensorimotor development remains to be fully understood. In this study, the catabolic enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) were inhibited either simultaneously or individually during the first ∼24 h of zebrafish embryogenesis, and the properties of contractile events and escape responses were studied in animals ranging in age from 1 day post-fertilization (dpf) to 10 weeks. This perturbation of the eCS resulted in alterations to contractile activity at 1 dpf. Inhibition of MAGL using JZL 184 and dual inhibition of FAAH/MAGL using JZL 195 decreased escape swimming activity at 2 dpf. Treatment with JZL 195 also produced alterations in the properties of the 2 dpf short latency C-start escape response. Animals treated with JZL 195 exhibited deficits in escape responses elicited by auditory/vibrational stimuli at 5 and 6 dpf. These deficits were also present during the juvenile developmental stage (8- to 10-week-old fish), demonstrating a prolonged impact to sensory systems. These findings demonstrate that eCS perturbation affects sensorimotor function, and underscores the importance of eCB signaling in the development of motor and sensory processes.

The endocannabinoid system's involvement in motor development relies on cannabinoid receptors, TRP channels, and Sonic Hedgehog signaling.

The endocannabinoid system (eCS) plays critical roles in locomotor function and motor development; however, the roles of non-canonical cannabinoid receptor systems such as transient receptor potential (TRP) channels and the Sonic Hedgehog (SHH) signaling pathway in conjunction with the eCS in sensorimotor development remains enigmatic. To investigate the involvement of canonical and non-canonical cannabinoid receptors, TRP channels, and the SHH pathway in the development of sensorimotor function in zebrafish, we treated developing animals with pharmacological inhibitors of the CB1R, CB2R, TRPA1/TRPV1/TRPM8, and a smoothened (SMO) agonist, along with inhibitors of the eCS catabolic enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) during the first ~24 h of zebrafish embryogenesis. Locomotor function was examined by assessing touch-evoked escape swimming at 2 days post-fertilization. We report that FAAH inhibition had no effect on swimming while MAGL inhibition using JZL 184 reduced swimming distance and the dual FAAH/MAGL inhibitor JZL 195 impaired swimming distance and mean swimming velocity. The CB1R antagonist AM 251 prevented locomotor deficits caused by eCS perturbation but the CB2R antagonist AM 630 did not. Inhibition of TRPA1/TRPV1/TRPM8 using AMG 9090 rescued the locomotor reductions caused by FAAH/MAGL inhibition, but not by MAGL inhibition alone. The SMO agonist purmorphamine attenuated the effects of JZL 184 and JZL 195 on swimming distance, but not mean velocity. Together, these findings provide one of the first investigations examining the interactions between the eCS and its non-canonical receptor systems in vertebrate motor development.