A new subdivision, marginal division, in the neostriatum of the monkey brain

A new subdivision, the "marginal division" (MrD), was discovered at the cau dal border of the striatum and surrounds the rostral edge of the globus pal lidus in the rat brain in our previous studies. The neuronal somata of the MrD are mostly fusiform in shape with their long axes lining dorsoventrally , The MrD is more densely filled with substance P (SP)-, Leucine-enkephalin (L-Enk)-, dynorphin B-, neurotensin-, somatostatin- and cholecystokinin (C CK)-immunoreactive fibers and terminal-like structures than the rest of the striatum. The MrD was confirmed in the cat neostriatum as well. The presen t study intended to explore whether the MrD exists in the monkey neostriatu m (putamen) with Nissl, histochemical and immunohistochemical methods. A ba nd of fusiform neurons were obviously identified at the caudomedial edge of the putamen. These neurons lie outside the lateral medullary lamina and in directly surround the rostrolateral border of the globus pallidus. The abun dance of SP-, L-Enk-, neuropeptide Y-, CCK-, dopamine and serotonin-positiv e fibers and terminal-like structures with a few positive fusiform neurons accumulating at the caudomedial border of the putamen obviously distinguish es this zone from the rest of neostriatum and globus pallidus. The acetylch olinesterase (AChE) positive and nicotinamide adenine dinucleotide phosphat e diaphorase (NADPH-d) containing fusiform neurons are distinctly Visualize d in the same zone. The morphological figure and the location of these neur ons, and the histochemical and immunohistochemical characteristics of this area coincide well with those of the MrD in the rat and cat striatum. This study thus convincingly identifies the existence of the MrD in the monkey n eostriatum. It is fairly asserted that the MrD is a universal structure in the mammalian brain.