IC50: 220 nM (GPR171).

MS21570 significantly attenuates this CNO-mediated increase in food intake. Interestingly, MS21570 causes a significant increase in center time compared to vehicle suggesting an effect on the anxiety-like behavior. Intra-BLA administration of MS21570 leads to an increase in open arm time on the elevated plus maze although there is no effect on locomotor activity during this test. Interestingly, when administered before and immediately following fear conditioning, MS21570 significantly attenuates freezing measured 24 hours later. Behavioral differences between systemic and intra-BLA administration of MS21570 could be due to the pharmacokinetic and pharmacodynamic properties of the drug. Further studies are needed to characterize the GPR171 antagonist.