A Study on the Effect of Deoxynivalenol on Serotonin Receptor Binding in Pig Brain Membranes

Central serotoninergic (5-hydroxytryptamine, 5HT) pathways are believed to be involved in the mechanisms of anorexia and/or emesis evoked by the trichothecene mycotoxin deoxynivalenol (DON). Using an in vitro membrane receptor binding assay, the competitive potency of DON was investigated against several radioactive ligands that have a high affinity for selective 5HT receptor subgroups. Receptor site densities and displacement profiles in twelve selected regions of pig brain were investigated. Overall, DON possessed only minimal efficacy to competently block any of the 5HT-ligands tested. IC50 values (50% inhibitory concentration) of at least 5 mM DON were required to inhibit binding, and in certain regions concentrations of 100 mM were ineffective. In comparison, several standard 5HT-antagonists showed 10(3)-10(5) times greater capability than DON to displace binding of these ligands. Because these results indicated DON possesses only weak affinity for the 5HT-receptor subtypes investigated here, this suggested that in vivo, unless relatively high concentrations of the toxin are present, its pharmacological effects may be mediated by mechanisms other than a functional interaction with serotoninergic receptors at the central level.