EXPERIMENTS were performed to assess the number and parvalbumin (PV) immuno
reactivity of neurons participating in the pallidostriatal projection in ma
caque monkeys. Injection of WGA-HRP into the right caudate nucleus and the
left putamen of a Macaca mulatta and a M. fuscata labeled a large number of
the globus pallidus external segment (GPe) neurons. Counting neurons label
ed with WGA-HRP and those stained with neuronal markers indicated that simi
lar to 30% of GPe neurons project to neostriatum. Approximately 2/3 of the
pallidostriatal neurons are PV-immunoreactive. This study revealed that a s
ignificant number of primate GPe PV immunoreactive neurons pro]ect to the n
eostriatum, and suggest that the pallidostriatal projection should be taken
into account in the analysis of functional roles of the basal ganglia circ
uitry. NeuroReport 10:1467-1472 (C) 1999 Lippincott Williams & Wilkins.