The neostriatal mosaic: compartmental distribution of calcium-binding protein and parvalbumin in the basal ganglia of the rat and monkey.

TLDR

Calcium‑binding protein (CaBP) and parvalbumin are expressed in the brain and bind calcium in the micromolar range, and prior work has shown that striatal matrix neurons project to the substantia nigra pars reticulata while patch neurons project to the pars compacta. The study examines how the distinct distributions of CaBP and parvalbumin in the basal ganglia may serve as intracellular calcium buffers influencing neuronal response properties. The immunohistochemical distribution of these two proteins was examined in the basal ganglia of rats and rhesus monkeys. CaBP immunoreactivity is confined to matrix‑projecting striatonigral neurons and their afferent fibers in the substantia nigra pars reticulata, whereas parvalbumin labels a subset of substantia nigra pars reticulata neurons, their axons, and some medium‑sized aspiny interneurons in the lateral striatum, reflecting distinct compartmental distributions linked to matrix and patch compartments.

Abstract

Calcium-binding protein (CaBP) and parvalbumin are two proteins that are expressed in brain and bind calcium in the micromolar range. The immunohistochemical distribution of these two proteins was examined in the basal ganglia of rats and rhesus monkeys. In the striatum, CaBP immunoreactivity is localized to a subset of striatonigral projection neurons; CaBP-positive neurons are distributed in areas containing somatostatin-immunoreactive fibers and not in the complementary areas containing dense mu opiate-receptor binding. These biochemical labels mark, respectively, the matrix and patch compartments of the striatum. Previous studies have shown that striatal matrix neurons project to the substantia nigra pars reticulata, whereas striatal patch neurons project to the substantia nigra pars compacta. Consistent with the restricted localization of CaBP in the matrix projection neurons is the confinement of CaBP-immunoreactive afferent fibers to the pars reticulata. CaBP is also localized to a portion of dopaminergic and a few nondopaminergic neurons in the substantia nigra pars compacta and in most dopaminergic neurons in the ventral tegmental area. Parvalbumin immunoreactivity is localized to a subset of substantia nigra pars reticulata neurons and their axons. In the lateral striatum, some medium-sized aspiny interneurons are also parvalbumin immunoreactive. The distinct distributions of CaBP and parvalbumin in the basal ganglia are discussed in terms of their possible roles as intracellular calcium buffer systems related to the physiologic response properties of the neurons in which they are contained.