AP521 is an agonist of human 5-HT1A receptor (IC50s: 135, 94, 254, 5530, 418, 422 and 198 nM for 5-HT1A (rat), 5-HT1A (human), 5-HT1B (rat), 5-HT1B (human), 5-HT1D (human), 5-HT5a (human) and 5-HT7 (rat)). AP521 also decreases the forskolin-induced cAMP accumulation from 10 nM to 10 μM.

AP521 significantly increases the number of shock acceptances at doses between 0.5 to 10 mg/kg. Oral administration of AP521 at 3 and 10 mg/kg significantly decreases freezing time. AP521 significantly increases the time spent on the open arms by approximately 2-fold as compared to the vehicle-treated group [F(3, 36)=4.21, P<0.05 for AP521]. The anxiolytic-like effect of AP521 appears to be dose-related. AP521 significantly increases the extracellular 5-HT level of the medial prefrontal cortex (mPFC) at 10 mg/kg from 0.5 to 1 h after administration. AP521 at 3 mg/kg tends to increase the extracellular 5-HT level, however, this increase is not significant.