Nucleus accumbens acetylcholine regulates appetitive learning and motivation for food via activation of muscarinic receptors.

These experiments tested whether nucleus accumbens muscarinic or nicotinic acetylcholine receptor activation is required for rats to learn to lever press for sucrose. Muscarinic blockade with scopolamine (1.0 microg/side or 10.0 microg/side), but not nicotinic antagonism with mecamylamine (10.0 microg/side), inhibited learning and performance when applied to the core or shell. Further experiments showed that acute accumbens scopolamine treatment increased locomotor activity and reduced sucrose consumption. However, microanalyses of behavioral events in the instrumental chamber revealed that reductions of lever press performance during muscarinic blockade were not due to gross motor dysfunction. Accumbens core scopolamine was subsequently shown to reduce the amount of work rats would expend under a progressive ratio paradigm. These novel results implicate nucleus accumbens muscarinic receptors in the modulation of appetitive learning, performance, and motivation for food.