Immunoreactivity for calcium-binding proteins in the claustrum of the monkey

The claustrum is topographically and reciprocally connected with many diffe rent cortical areas, and anatomical and physiological data suggest it is co mposed of functionally distinct subdivisions. We asked if the distribution of cells immunoreactive for three calcium-binding proteins, parvalbumin, ca lbindin D-28k and calretinin would delineate functional subdivisions in the claustrum. We also asked if, as in cortex, different cell types were immun oreactive for the different proteins. We found that cells with parvalbumin- ir were large, multipolar cells. Cells immunoreactive for calretinin were b ipolar cells with elongated cell bodies and beaded dendrites. There were th ree different types of cells immunoreactive for calbindin. The most numerou s were small cells with round or oval cell bodies and numerous fine, windin g processes. A second type were large multipolar, cells that resembled the parvalbumin-ir cells. The third class were bipolar cells with large, elonga ted cell bodies. Each type of cell resembles a cell type described in earli er Golgi studies, and each has a morphological cortical counterpart. While the different cell types varied in density, each was seen over the anterior -posterior and dorsal-ventral extent of the claustrum.