Dopamine — Acetylcholine Interactions

Abstract

Dopamine-acetylcholine interactions can take place within and outside the striatum. In the striatum, cholinergic neurons are large aspiny interneurons that comprise 1%–3% of the total neuronal population of the striatum in rats (Fibiger 1982; Phelps et al. 1985) and monkeys (Mesulam et al. 1984; Difiglia 1987), and by virtue of their dendritic arborization extend over large territories in the striatum (Woolf 1991). Striatal cholinergic neurons receive direct excitatory glutamatergic inputs from the cortex and in particular from the parafascicular thalamus (Lapper and Bolam 1992) and dopaminergic inputs from substantia nigra pars compacta (Kubota et al. 1987). Striatal cholinergic neurons receive inhibitory and modulatory influences from various interneurons and from γ-aminobutyric acid (GABA)ergic medium-size spiny neurons where they finally converge with DA neurons (Di Chiara et al. 1994a). Acetylcholine, on the other hand, modulates the function of dopamine mesencephalic neurons by an action on nicotinic receptors by virtue of cholinergic projections from pontomesencephalic cell groups (Garzon et al. 1999).