[3H]hemicholinium-3 binding in rabbit striatum: correspondence with patchy acetylcholinesterase staining and a method for quantifying striatal compartments

Comparisons were made of the distribution of acetylcholinesterase (AChE) staining and [3H]hemicholinium-3 binding in adjacent tissue sections through the rabbit striatum. The distribution of these two markers matched closely in all regions examined. Circumscribed AChE-poor zones (striosomes) were visible throughout the rostral one-third of the caudate nucleus and were aligned with areas of low [3H]hemicholinium-3 binding in adjacent sections. Quantitative analysis of the [3H]hemicholinium-3 film autoradiographs revealed a 2- to 3-fold lower binding of [3H]hemicholinium-3 to sites within the striosome compartment compared with the darker background (matrix). Further analysis revealed at least 3 distinct levels of binding throughout the striatum. The results suggest a novel autoradiographic approach for identifying and quantifying striatal heterogeneities. Because [3H]hemicholinium-3 apparently labels the high-affinity choline transport complex associated with cholinergic neurons, the patchy striatal distribution of AChE/[3H]hemicholinium-3 apparently marks zones with differing densities of cholinergic neuron processes.