Acetylcholinesterase associated with dopaminergic innervation of the neostriatum: histochemical observations of a heterogeneous distribution.

Unilateral injections of 6-hydroxydopamine that damaged the mesotelencephalic dopaminergic projection resulted in decreased acetylcholinesterase (AChE) staining in the ipsilateral neostriatum. This reduction, which was most apparent in the posterior and medial anterior neostriatum, occurred in rats killed 3 days or more after the 6-hydroxydopamine injection. No hemispheric asymmetries of AChE staining were found in the medial nucleus accumbens septi, olfactory tubercle or amygdala. Thus, some of the AChE in the neostriatum appears to be localized to its dopaminergic innervation; however, the enzyme may be heterogeneously distributed throughout this structure's dopaminergic afferent fibers. AChE seems not to be associated with dopaminergic axons innervating the limbic forebrain.