[Efferent connections of the caudate nucleus of the cat studied using retrograde axonal transport of horseradish peroxidase].

The origin of descending efferent pathways from the caudate nucleus was studied by retrograde axonal transport of horseradish peroxidase. Widespread topically organized projections were observed to the paleostriatum and the substantia nigra and less numerous to the thalamus. The main source of these projections were small and medium-size cells. A particular role of the subthalamic nucleus in the descending efferent system of the caudate nucleus is pointed out: this nucleus besides projections to the caudate nucleus itself possesses direct connections with principal output structures of the latter--the the paleostriatum and substantia nigra.