A pallidostriatal projection in the cat and monkey.

Using the retrograde transport of horseradish peroxidase-labeled wheat germ agglutinin, a direct projection from the globus pallidus to the caudate nucleus and putamen was shown in the cat. The retrograde transport of the fluorescent dye Granular blue was used in a squirrel monkey to demonstrate a similar projection from the external pallidal segment to the putamen. No cell-labeling occurs in the cat's entopeduncular nucleus or the monkey's internal pallidal segment. In the cat, the pallidostriatal neurons are found in all parts of the globus pallidus and project throughout the striatum. However, the pallidostriatal projection is topographically organized such that it reciprocates the topography of the striatopallidal projection.