Organization of the striatal projections from the rostral caudate nucleus to the globus pallidus, the entopeduncular nucleus, and the pars reticulata of the substantia nigra in the cat.

Abstract

This study explores the organization of the striatal projections from the rostral caudate nucleus to the output nuclei of the basal ganglia in the cat. Tracer deposits were stereotaxically injected in different dorsoventral, mediolateral, and rostrocaudal sectors of the head of the caudate nucleus using horseradish peroxidase (HRP) conjugated with wheat germ agglutinin (HRP-WGA) either alone or mixed with free HRP. After the injections, a detailed analysis of the terminal labeling was carried out within the globus pallidus (GP), the entopeduncular nucleus (Ep), and the substantia nigra (SN) pars reticulata (SNR). Our findings illustrate how different dorsoventral, mediolateral, and rostrocaudal parts of the rostral caudate nucleus project primarily to similarly positioned but spatially segregated parts of GP. The striatoentopeduncular pathway was also organized topographically, but there was overlapping by projections from different parts of the rostral caudate nucleus. Areas of topographical segregation and zones of overlap were detected in the organization of the striatal projections from the rostral caudate nucleus to SNR. These results raise the possibility of distinct striatal actions upon different sectors of the output nuclei of the basal ganglia and, indirectly, upon their targets in the thalamus and brainstem.