ABSTRACT
The striatum contains a population of cholinergic neurons which can be revealed by acetylcholinesterase histochemistry or choline acetyltransferase immunohistochemistry. Striatal cholinergic neurons receive synaptic inputs from two major extrinsic sources: mesencephalic dopaminergic neurons and glutamatergic neurons arising from the thalamus or, less frequently, from the cerebral cortex. The aspiny neurons also receive glutamatergic inputs and project to cholinergic neurons and medium spiny neurons. Reciprocal regulation of cholinergic neurons by enkephalin is indicated by the prevalent distribution of delta opioid receptors on cholinergic interneurons and the fact that delta opioid agonists inhibit acetylcholine release. Glutamatergic terminals make asymmetrical synaptic contacts with striatal neurons, including medium-sized spiny projection neurons and aspiny interneurons. Glutamatergic regulation of immediate early genes and neuropeptide expression in the striatum may be an essential element of the neuronal adaptation which underlies the delayed or long-term effects of psychotropic agents.
