Visceral pain-related acute actions of cerulein on mouse and human sensory neurons

Cerulein is an orthologue of cholecystokinin, which is often used to induce acute pancreatitis in pre-clinical studies. In these models, animals show signs of pain, and this is the most common complaint of patients with acute pancreatitis. However, little is known about how this pain is mediated, the role of cerulein murine pain responses, or its relevance to human pancreatitis pain. We injected 25 or 50 µg/kg cerulein intraperitoneally into male and female mice and assessed pain behaviors using the von Frey test of mechanical hypersensitivity. The excitability of mouse and human visceral dorsal root ganglia (DRG) neurons was assessed using whole-cell patch-clamp electrophysiology. Pharmacology was performed using commercial antagonists of cholecystokinin (CCK) A or B receptors. We show that pain behaviors developed similarly in male and female cerulein-injected mice and that visceral DRG from these mice exhibited increased excitability compared to controls. Direct application of cerulein to T8-L2 mouse and human DRG showed increased excitability compared to controls consistent with DRG from cerulein-injected mice. The actions of cerulein on visceral DRG neurons were attributed to CCK-A, but not CCK-B receptor. A similar response to cerulein was observed in human thoracic DRG neurons. These findings highlight the importance of the cholecystokinin system, particularly the CCK-A receptor, to visceral pain including pancreatitis through direct sensitization of visceral DRG neurons from mice or humans.