The localization of acetylcholinesterase in the corpus striatum and substantia nigra of the rat following kainic acid lesion of the corpus striatum: a biochemical and histochemical study.

The distribution of acetylcholinesterase in the corpus striatum and substantia nigra was examined with the use of kainic acid lesions of the corpus striatum and pharmacohistochemical experiments. Histochemically identified acetylcholinesterase-containing neurons in the striatum were among those which were destroyed by kainic acid. Complementary biochemical studies demonstrated that approximately 50% of the total acetylcholinesterase activity in the striatum was localized in these acetylcholinesterase-containing neurons. Intrastriatal injections of kainic acid produced a substantial decrease in the activity of the glutamic acid decar?ylase in the substantia nigra, thus demonstrating that neurons contributing to the striato- and/or pallidonigral pathways had been lesioned. However, nigral acetylcholinesterase activity was not significantly reduced by the striatal kainic acid injections. Furthermore, stereotaxic injections of colchicine along the course of the striatonigral projection failed to produce an accumulation of acetylcholinesterase in these fibers proximal to the injection. In contrast, injections of colchicine into the nigrostriatal projection led to a proximal accumulation of acetylcholinesterase in the fibers of this system, thus confirming the presence of acetylcholinesterase in the ascending dopaminergic neurons.It is concluded that the striato- and pallidonigral projections in the rat do not contain significant levels of acetylcholinesterase. Furthermore, acetylcholinesterase-containing neurons in the striatum appear to be interneurons rather than the source of striatal efferents. It is suggested that some of these acetylcholinesterase-containing neurons may be striatal cholinergic interneurons.