Localization of dopamine D2 receptors on cholinergic interneurons of the dorsal striatum and nucleus accumbens of the rat.

Striatal cholinergic interneurons located in the dorsal striatum and nucleus accumbens are amenable to influences of the dopaminergic mesolimbic pathway, which is a pathway involved in reward and reinforcement and targeted by several drugs of abuse. Dopamine and acetylcholine neurotransmission and their interactions are essential to striatal function, and disruptions to these systems lead to a variety of clinical disorders. Dopamine regulates acetylcholine release through dopamine receptors that are localized directly on striatal cholinergic interneurons. The dopamine D2 receptor, which attenuates acetylcholine release, has been implicated in drug relapse and is targeted by therapeutic drugs that are used to treat a variety of neurological disorders including Tourette Syndrome, Parkinson's disease and schizophrenia. The present study provides the first direct evidence for the localization of dopamine D2 receptors on striatal cholinergic interneurons of the rat brain using dual labeling immunocytochemistry procedures. Using light microscopy, dopamine D2 receptors were localized on the cell somata and dendritic and axonal processes of striatal cholinergic interneurons in the dorsal striatum and nucleus accumbens of the rat brain. These findings provide a foundation for understanding the specific roles that cholinergic neuronal network systems and interacting dopaminergic signaling pathways play in striatal function and in a variety of clinical disorders including drug abuse and addiction.