Pancreatic oedema occurs early in the development of
acute pancreatitis, and the overall extent of fluid loss correlates with disease severity. The
tachykinin substance P (SP) is released from sensory nerves, binds to the
neurokinin-1 receptor (NK1-R) on endothelial cells and induces plasma extravasation, oedema, and neutrophil infiltration, a process termed
neurogenic inflammation. We sought to determine the importance of neurogenic mechanisms in
acute pancreatitis. Pancreatic plasma extravasation was measured using the intravascular tracers
Evans blue and Monastral blue after administration of specific NK1-R agonists/antagonists in rats and NK1-R(+/+)/(-/-) mice. The effects of NK1-R genetic deletion/antagonism on pancreatic plasma extravasation,
amylase,
myeloperoxidase (MPO), and histology in
cerulein-induced
pancreatitis were characterized. In rats, both SP and the NK1-R selective agonist [Sar(9) Met(O(2))(11)]SP stimulated pancreatic plasma extravasation, and this response was blocked by the NK1-R antagonist
CP 96,345. Selective agonists of the
NK-2 or
NK-3 receptors had no effect. In rats,
cerulein stimulated pancreatic plasma extravasation and serum
amylase. These responses were blocked by the NK1-R antagonist
CP 96,345. In wildtype mice, SP induced plasma extravasation while SP had no effect in NK1-R knockout mice. In NK1-R knockout mice, the effects of
cerulein on pancreatic plasma extravasation and
hyperamylasemia were reduced by 60%, and pancreatic MPO by 75%, as compared to wildtype animals. Neurogenic mechanisms of
inflammation are important in the development of inflammatory oedema in acute interstitial
pancreatitis.