TLQP-21 TFA, a VGF-derived peptide endowed of endocrine and extraendocrine properties, is a potent G-protein-coupled receptor complement-3a receptor1 (C3aR1) agonist (EC50: mouse TLQP-21=10.3 μM; human TLQP-21=68.8μM). TLQP-21 TFA activates C3aR1 to induce an increase of intracellular Ca2+. TLQP-21 TFA is used for the research in regulation of nociception and other relevant physiologic functions.