Striatal muscarinic receptor antagonism reduces 24-h food intake in association with decreased preproenkephalin gene expression

Cholinergic interneurons of the striatum respond to motivationally relevant stimuli and are involved in appetitive learning. However, there has been relatively little inquiry into the role of striatal acetylcholine in food motivation. Here we show in rats that a single infusion of the muscarinic receptor antagonist scopolamine (0, 5.0 or 10.0 mu g/0.5 mu L bilaterally) potently reduced 24-h food intake following injections into either the ventral or dorsal striatum, without affecting water intake. Furthermore, muscarinic receptor blockade induced reliable and widespread reductions in striatal preproenkephalin, but not preprodynorphin, mRNA expression. These data suggest a novel role for striatal acetylcholine in modulating feeding behavior via its effects on enkephalin gene expression. As prior research indicates a critical role for striatal enkephalin in consummatory behaviors and palatability, we hypothesize that cholinergic interneurons assist in translating hypothalamic energy state signals into food-directed behaviors via their regulation of striatal opioid peptides.