Medium-throughput zebrafish optogenetic platform identifies deficits in subsequent neural activity following brief early exposure to cannabidiol and Δ9-tetrahydrocannabinol

Abstract

In light of legislative changes and the widespread use of cannabis as a recreational and medicinal drug, delayed effects of cannabis upon brief exposure during embryonic development are of high interest as early pregnancies often go undetected. Here, zebrafish embryos were exposed to cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC) until the end of gastrulation (1–10 h post-fertilization) and analyzed later in development (4–5 days post-fertilization). In order to measure neural activity, we implemented Calcium-Modulated Photoactivatable Ratiometric Integrator (CaMPARI) and optimized the protocol for a 96-well format complemented by locomotor analysis. Our results revealed that neural activity was decreased by CBD more than THC. At higher doses, both cannabinoids could dramatically reduce neural activity and locomotor activity. Interestingly, the decrease was more pronounced when CBD and THC were combined. At the receptor level, CBD-mediated reduction of locomotor activity was partially prevented using cannabinoid type 1 and 2 receptor inhibitors. Overall, we report that CBD toxicity occurs via two cannabinoid receptors and is synergistically enhanced by THC exposure to negatively impact neural activity late in larval development. Future studies are warranted to reveal other cannabinoids and their receptors to understand the implications of cannabis consumption on fetal development.

A Review on the Bioactivity of Cannabinoids on Zebrafish Models: Emphasis on Neurodevelopment

“…Considering the deleterious effects of THC and CBD on developing embryos, the impact of these compounds on neural activity has recently been investigated through a novel in vivo assay based on a calcium-modulated photoactivatable ratiometric integrator (CaMPARI) system, which is able to provide a practical read-out of the neural activity in freely swimming larvae [ 3 ].…”

“…For centuries, the cannabis plant ( Cannabis sativa and Cannabis indica ) has been used as a source of food, fiber, and medicine [ 1 , 2 , 3 , 4 ]. In recent decades, scientific interest in cannabis has increased considerably, as its bioactive compounds have shown promising potential in the treatment of numerous musculoskeletal and neurological diseases in humans [ 5 , 6 ].…”

“…Among young people, cannabis is the illicit substance that is most commonly used for recreational purposes [ 5 , 7 , 8 ], thanks to its anxiolytic effect and the associated sense of euphoria [ 9 ]. It is also widely used among pregnant women, mainly to reduce morning sickness, nausea, and vomiting [ 3 , 10 ]. However, because cannabinoids can readily cross the placenta and reach the fetus, they may impact the development of the embryo, which increases the risk of neurological disorders in newborns [ 3 ].…”

“…It is also widely used among pregnant women, mainly to reduce morning sickness, nausea, and vomiting [ 3 , 10 ]. However, because cannabinoids can readily cross the placenta and reach the fetus, they may impact the development of the embryo, which increases the risk of neurological disorders in newborns [ 3 ]. The mechanistic pathways by which cannabis and its metabolites affect neurodevelopment and nervous-system functioning remain poorly understood and need to be further investigated.…”

“…By activating the G α subunit, cannabinoids are able to inhibit voltage-gated calcium channels and potentiate inwardly rectifying potassium channels [ 61 ]. Even though CBD interacts with both cannabinoid receptors, it shows lower affinity compared with THC [ 3 ]. Indeed, CBD seems to be 10 times less active than THC on both CB 1 and CB 2 [ 48 ].…”