The fact that mesolimbic DA plays a major role in modulating ingestive related behavior is now well documented. However, the neurochemical history of the corpus striatum is replete with suggestions that DA does not act in isolation but combines its action at least in part with that of the cholinergic system [11,48–51]. In addition to a mesencephalic dopamine input, the caudate and accumbens nuclei contain cholinergic interneurons [52–54], and there are numerous indications that the two systems functionally interact in the striatum [55–59]. Moreover, in the clinical arena, the prescription of dopaminergic antagonists (e.g. for the treatment of psychosis) is usually accompanied by co-administration of anticholinergic agents. Given the history of cholinergic-dopaminergic interactions in the striatum and the similar anatomical connectivity of the subjacent nucleus accumbens, it seemed reasonable to explore the possibility that both DA and ACh may have a combined role in the modulation of motivated behaviors.
