Figure 1.

Cannabinoid receptor (CB) anandamide (AEA) binding model. AEA partitions into the cell membrane due to its high lipophilicity (log D7.4 = 5.7). It then diffuses laterally to the binding site of the cannabinoid receptor CB1 (after Tian et al.). Observed binding can then be given by the product of the partition coefficient and the binding affinity, as shown in the figure (after Vauquelin and Packeu). Hence, observed affinity (dissociation constant K_D) is approximately the receptor binding affinity K_D′(200 nmol/l) × K_p⁻¹ (2.1 × 10⁻⁶) = 0.4 pmol/l.