Substance p An 11-amino acid peptide Released from primary afferent nociceptors Biological activities Potentⅴ asodilator Degranulates mast cell Chemoattractant for leukocytes Inflammatory mediatorSubstance P • An 11- amino acid peptide • Released from primary afferent nociceptors • Biological activities: Potent vasodilator Degranulates mast cell Chemoattractant for leukocytes Inflammatory mediator