AY-NH2 is a peptide agonist of proteinase-activated receptor 4 (PAR4) that induces aggregation of rat and human platelets in vitro (EC50s = 15 and 60 μM, respectively).It reduces expression of glycoprotein (GP) Ib, and increases expression of GPIIb/IIIa on the surface of human platelets.AY-NH2 induces relaxation of isolated rat aortic rings and contraction of rat gastric longitudinal muscle strips (EC50s = 11 and 110 μM, respectively) as well as inhibits calcium mobilization evoked by capsaicin in rat sensory neurons.In vivo, AY-NH2 (1-100 μg) increases latency to paw withdrawal and the nociceptive threshold in response to thermal and mechanical stimuli.AY-NH2 (200 μg) also increases paw thickness in a rat paw edema assay.
