ZFIN ID: ZDB-PUB-190627-7
Altered Swimming Behaviors in Zebrafish Larvae Lacking Cannabinoid Receptor 2
Acevedo-Canabal, A., Colón-Cruz, L., Rodriguez-Morales, R., Varshney, G.K., Burgess, S., González-Sepúlveda, L., Yudowski, G., Behra, M.
Date: 2019
Source: Cannabis and cannabinoid research   4: 88-101 (Journal)
Registered Authors: Behra, Martine, Burgess, Shawn, Varshney, Gaurav
Keywords: AM-360, JWH-133, PTZ, VPA, cannabinoid receptor 2 knockout, zebrafish larva
MeSH Terms: none
PubMed: 31236475 Full text @ Cannabis Cannabinoid Res
Background and Objectives: The cannabinoid receptor 2 (CB2) was previously implicated in brain functions, including complex behaviors. Here, we assessed the role of CB2 in selected swimming behaviors in zebrafish larvae and developed an in vivo upscalable whole-organism approach for CB2 ligand screening. Experimental Approach: Using CRISPR-Cas9 technology, we generated a novel null allele (cnr2upr1 ) and a stable homozygote-viable loss-of-function (CB2-KO) line. We measured in untreated wild-type and cnr2upr1/upr1 larvae, photo-dependent (swimming) responses (PDR) and center occupancy (CO) to establish quantifiable anxiety-like parameters. Next, we measured PDR alteration and CO variation while exposing wild-type and mutant animals to an anxiolytic drug (valproic acid [VPA]) or to an anxiogenic drug (pentylenetetrazol [PTZ]). Finally, we treated wild-type and mutant larvae with two CB2-specific agonists (JWH-133 and HU-308) and two CB2-specific antagonists, inverse agonists (AM-630 and SR-144528). Results: Untreated CB2-KO showed a different PDR than wild-type larvae as well as a decreased CO. VPA treatments diminished swimming activity in all animals but to a lesser extend in mutants. CO was strongly diminished and even more in mutants. PTZ-induced inverted PDR was significantly stronger in light and weaker in dark periods and the CO lower in PTZ-treated mutants. Finally, two of four tested CB2 ligands had a detectable activity in the assay. Conclusions: We showed that larvae lacking CB2 behave differently in complex behaviors that can be assimilated to anxiety-like behaviors. Mutant larvae responded differently to VPA and PTZ treatments, providing in vivo evidence of CB2 modulating complex behaviors. We also established an upscalable combined genetic/behavioral approach in a whole organism that could be further developed for high-throughput drug discovery platforms.