FIGURE 9.

Functions of tachykinins in the skin. SP and NKA are released from the peripheral endings of primary sensory nerves in the skin. They act on keratinocytes via NK₁R and NK₂R to activate NF-κB and promote release of cytokines and chemokines. SP and NKA act within the vasculature to induce plasma extravasation and to upregulate adhesion factors that stimulate neutrophil adhesion and infiltration. During inflammation, SP and NKA activate mast cells, neutrophils, and Langerhans cells, which amplifies the inflammatory response. Centrally released tachykinins contribute to pain and itch transmission.