Background/aims: Activation of intestinal mast cells and neurons is involved in intestinal inflammation and diarrhea. This study compared the effects of neuronal inhibitors and inhibition of intestinal sensory afferent nerves on the intestinal actions of Clostridium difficile toxin A, an inflammatory enterotoxin, and cholera toxin, a noninflammatory enterotoxin.
Methods: The effects of lidocaine, hexamethonium, atropine, and long-term pretreatment of capsaicin on fluid secretion, mannitol permeability, myeloperoxidase (MPO) activity, and release of rat mast cell protease II (RMCPII) were measured in toxin A- and cholera toxin-exposed loops in vivo.
Results: Lidocaine, hexamethonium, and capsaicin, but not atropine, inhibited toxin A-mediated secretion and MPO activity, but only capsaicin reduced mannitol permeability. Lidocaine, but not capsaicin, reduced secretion and permeability caused by cholera toxin. Toxin A caused release of RMCPII from rat ileum in vivo and in vitro; this was inhibited by lidocaine or capsaicin, whereas cholera toxin had no effect on release of RMCPII.
Conclusions: Neuronal mechanisms are important in the in vivo effects of these two enterotoxins. Capsaicin-sensitive sensory afferent neurons and mast cells are involved in the intestinal mechanism of toxin A, but not cholera toxin.