Aflatoxins are a group of mycotoxins produced by toxigenic strains of Aspergillus flavus, Aspergillus parasiticus and Aspergillus nomius as secondary metabolites. Most of the studies on the aflatoxins have focused mainly on their chronic toxic effects but aflatoxins have also a lot of acute effects on the respiratory, cardiovascular and gastrointestinal systems. In this study the acute gastrointestinal effects of the aflatoxins on rat isolated ileum and the possible mechanisms underlying contractile responses to them were investigated. Aflatoxin increased both of the amplitude and the frequency of spontaneous contractions in a dose-dependent manner. Pretreatment with a cholinergic system inhibitor, atropine sulfate (23.6 nM), a specific sodium-channel blocker, tetrodotoxin (0.3 mu M) and an inhibitor of ACh release from terminal motor neurons, morphine (0.3 mu M) decreased both of aflatoxin induced spontaneous contractions' amplitude and frequency, in contrast a nicotinic ganglionic blocker, hexamethonium chloride (55 mu M) did not change the aflatoxin effect. But the decrease of amplitude was more than the frequency in the presence of these antagonists. In conclusion, these findings of aflatoxin on isolated rat ileum may explain their acute gastrointestinal effects in humans and animals. (C) 2008 Elsevier Ltd. All rights reserved.