Cannabinoid Receptor 1, Brain (CNR1), also known as CB1 receptor, is a type of G protein-coupled receptor found predominantly in the central nervous system. It is the primary receptor for cannabinoids, the active components of cannabis, and plays a key role in the physiological and psychoactive effects of cannabis. CNR1 is primarily localized to neurons in the brain, where it is involved in various functions, including pain sensation, memory, appetite, mood, and cognition.Dopamine Receptor D2 (DRD2) can interact with CNR1 to regulate the distribution of dopamine.Thus a functional ELISA assay was conducted to detect the interaction of recombinant rat CNR1 and recombinant human DRD2.Briefly, CNR1 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to DRD2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-CNR1 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 μL stop solution to the wells and read at 450/630nm immediately. The binding activity of recombinant rat CNR1 and recombinant human DRD2 was shown in Figure 1, the EC50?for this effect is 0.43ug/mL.