The two main receptors in the endocannabinoid system are CB1 and CB2. Where THC directly affects these receptors, CBD has a subtler, more indirect approach. Instead of attaching to these receptors, CBD affects how these receptors signal the body and its chemicals. Furthermore, CBD increases the production of the body’s own cannabinoids by blocking the enzymes that can break them down.
Cannabidiol has low affinity for the cannabinoid CB1 and CB2 receptors, although it can act as an antagonist of CB1/CB2 agonists despite this low affinity. Cannabidiol may be an antagonist of GPR55, a G protein-coupled receptor and putative cannabinoid receptor that is expressed in the caudate nucleus and putamen in the brain. It also may act as an inverse agonist of GPR3, GPR6, and GPR12. CBD has been shown to act as a serotonin 5-HT1A receptor partial agonist. It is an allosteric modulator of the μ- and δ-opioid receptors as well. The pharmacological effects of CBD may involve PPARγ agonism and intracellular calcium release.