Nuclear magnetic resonance for studying recognition processes between anandamide and cannabinoid receptors

The understanding of the molecular basis of cannabinoid activity has greatly improved since the discovery of CB1 and CB2 receptors. In this paper, the ligand binding processes between the endogenous cannabimimetic ligand, anandamide (AEA), and the cannabinoid receptors from different parts of rat brain were studied by nuclear magnetic resonance spectroscopy. The NMR approach is based on the comparison of selective (R1(SE)) and non-selective (R1(NS)) proton spin-lattice relaxation rates of the ligand in the presence and absence of macromolecular receptors, as well as R1(NS) and R1(SE) temperature dependency analysis. From these studies, the ligand-receptor binding strength was evaluated on the basis of the calculation of the "affinity index". The derivation of the "affinity index" from chemical equilibrium kinetics for all systems allowed the comparison of the ability of anandamide to interact with cannabinoid receptors present in different brain sectors.