RESUMO
Distension of the rat intestine causes a capsaicin-sensitive, pressure-dependent depressor response which is indicative of nociception. A hypersensitivity of jejunal distension which possibly involves tachykinin NK2 receptors and is restricted to areas with mast cell hyperplagia is observed in rats infected 30 days previously with Nippostrongylus brasiliensis. This study aimed to further investigate the role of mast cells, tachykinins and kinins in this intestinal hypersensitivity. The activity of a mast cell stabilizer (doxantrazole), kinin antagonists (des-Arg 10-[Leu9]-kallidin, B1, HOE 140, B2) and tachykinin antagonists (CP 99, 994, NK1, SR 142801, NK3) were tested against the distension-induced depressor responses in control and post-infected rats. The 30-day post-infection-induced hypersensitivity was significantly reduced by the mast cell stabilizer doxantrazole. The hypersensitivity had resolved in 90-day post-infected rats when mast cells levels had normalized. Des-Arg 10-[Leu9]-kallidin and HOE 140 did not inhibit the depressor responses in controls but produced a significant inhibition in 30-day post-infected rats. CP 99,994 inhibited the depressor responses in post-infected rats with an equal potency to that in control rats. SR 142801 was inactive in both groups. In conclusion, mast cells and kinin-mediated nociception appear to be involved in post-infection intestinal hypersensitivity whereas tachykinin NK1 and NK3 receptors do not.
