LOCALIZATION OF PARVALBUMIN-IMMUNOREACTIVE STRUCTURES IN PRIMATE CAUDATE-PUTAMEN

To investigate the morphology, distribution, and connections of parval bumin-containing neurones in the caudate-putamen of primates, perfuse- fixed sections were stained to reveal parvalbumin immunoreactivity. In agreement with previous observations, the caudate-putamen was rich in parvalbumin-positive neurones and neuropil. The neuropil staining was uneven such that the dense background staining was interspersed with zones of relatively weak staining. The distribution corresponded to th e striosome/matrix system as defined by substance P or met-enkephalin immunostaining in adjacent sections. Because parvalbumin-positive neur ones are present in regions known to project to the caudate-putamen an d the majority of parvalbumin-positive terminals in the matrix formed asymmetric synapses, it is concluded that the uneven staining is proba bly due to afferents of the neostriatum. The morphology of the parvalb umin-immunoreactive neurones varied between the striosomes and matrix; those in the matrix were smaller and possessed dendritic arborisation s that were relatively uniform, whereas those in the striosomes were g enerally more extensively stained and possessed a greater variation in their dendritic branching patterns. The dendrites frequently crossed the boundary between the striosomes and matrix. A population of giant parvalbumin-immunoreactive neurones was also observed in the putamen. Electron microscopic analysis revealed that, in addition to terminals forming asymmetric synapses, a smaller population formed symmetric syn aptic specialisations and are presumed to be derived from the local pa rvalbumin-immunoreactive neurones. Terminals of the latter group forme d synapses with medium-sized spiny neurones. Because parvalbumin-posit ive neurones receive input from the cortex, they may transmit cortical information to spiny neurones. (C) 1994 Wiley-Liss, Inc.