Neurokinin 1 and 2 receptors mediate cholera toxin secretion in rat jejunum.
BACKGROUND & AIMS: Substance P, a member of the tachykinin family, is a prosecretory neuropeptide distributed widely throughout the enteric nervous system. Implicated in inflammatory states, its role in enterotoxigenic water and electrolyte secretion is unclear. We assessed the effect of substance P antagonists and neurokinin receptor antagonists on cholera toxin-, Escherichia coli heat-labile enterotoxin (LT)-, and heat-stable enterotoxin (STa)-induced water secretion in an in vivo rat jejunal perfusion model. METHODS: Anesthetized adult male Wistar rats were pretreated with substance P antagonists (D-Pro(2), D-Trp(79), substance P, 0.1-3.0 mg/kg; or CP 96,345/4, 0.3-3 mg/kg) or neurokinin (NK)-1 (sendide, 1.0 mg/kg), NK-2 (GR83074, 1.0 mg/kg), or NK-3 ([Trp(7),betaAla(8)]NKA(4-10), 1.0 mg/kg) receptor antagonists. In a subgroup, extrinsic sensory afferents were ablated by pretreatment with capsaicin. Jejunal perfusion, with a plasma electrolyte solution containing a nonabsorbable marker, was undertaken after exposure to cholera toxin (25 microg), LT (25 microg), STa (200 microg/L), or saline. Results: Cholera toxin-induced water and electrolyte secretion was inhibited by the substance P antagonists and the NK-1 and NK-2 receptor antagonists, but not by the NK-3 receptor antagonist or by pretreatment with capsaicin. Neither LT- nor STa-induced secretions were affected by the pretreatments. CONCLUSIONS: Prosecretory pathways involving NK-1 and NK-2 receptors specifically mediate the actions of cholera toxin in the small intestine.[1]References
- Neurokinin 1 and 2 receptors mediate cholera toxin secretion in rat jejunum. Turvill, J.L., Connor, P., Farthing, M.J. Gastroenterology (2000) [Pubmed]
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