Flavor preferences conditioned by post-oral infusion of monosodium glutamate in rats

► Rats learn to prefer a flavor paired with post-oral infusion of 60 mM MSG over a flavor paired with water. ► Both gastric and duodenal infusion sites were effective, suggesting an intestinal origin of the reinforcing signal. ► Post-oral MSG reinforcement was not enhanced by adding 2 mM IMP to the infusion. ► The post-oral action of MSG could enhance preference for glutamate-rich foods.