“∆9 –Tetrahydrocannabinol (∆9-THC) and cannabidiol (CBD), major psychoactive constituents of marijuana, induce potentiation of pentobarbital-induced sleep in mice.
We have elucidated the mechanism of enhancement of the anesthetic effect of pentobarbital by cannabinoids.
These results suggest that binding of ∆9-THC to the CB1 receptor is involved in the synergism with pentobarbital, and that potentiating effect of CBD with pentobarbital may differ from that of ∆9-THC. We successfully demonstrated that ∆9-THC enhanced the anesthetic effect of pentobarbital through the CB1 receptor.”
https://www.ncbi.nlm.nih.gov/pubmed/30636988
“The pharmacological results indicate the effect of ∆9-THC co-administered with pentobarbital was a synergistic, but not additive, action in mice. Further evidence suggests the CB1 receptor plays an important role as a trigger in potentiating pentobarbital-induced sleep by ∆9-THC.”
https://link.springer.com/article/10.1007%2Fs11419-018-0457-2