SFNGGP-NH2 is a biologically active peptide that interacts with Protease-Activated Receptor 3 (PAR-3), a high-affinity thrombin receptor. Human cutaneous mast cells express PAR-3 mRNA, implicating a role in itch mechanotransduction, with both histamine-dependent and independent pathways reported. While PAR-3 alone does not induce itch, it may potentiate itch when co-expressed with PAR-4, enhancing thrombin's action. This suggests that PAR-3's primary function is not as a signal transmitter across the membrane, but rather as a cofactor necessary for PAR-4 activation.