DISTRIBUTION OF THE CALCIUM-BINDING PROTEINS, CALBINDIN D-28K AND PARVALBUMIN, IN THE SUBICULAR COMPLEX OF THE ADULT-MOUSE

The immunohistochemical localizations of two specific calcium binding proteins, calbindin D-28K (calbindin) and parvalbumin (PV) were examin ed in the subicular complex, that is, the subiculum, presubiculum, and parasubiculum, of the adult mouse and were compared in detail with st aining pattern of the acetylcholinesterase (AChE) histochemistry. The calbindin immunoreactivity exhibited a conspicuous regional and lamina r pattern of distribution, which somewhat resembled the AChE staining pattern but was apparently different from the latter in various points . The PV immunoreactivity also exhibited a characteristic regional dif ference, although less prominent, The subiculum could be divided into two subregions, intensely calbindin-immunoreactive (calbindin-IR) and AChE stained proximal subiculum and only faintly calbindin-IR and AChE stained distal subiculum. In the subiculum most of calbindin-IR neuro ns were pyramidal cells which were clustered in the superficial half o f the cell layer in the proximal subiculum and appeared to be segregat ed from calbindin negative pyramidal cells located in the distal subic ulum and in the basal part of the proximal subiculum. In the presubicu lum calbindin-IR neurons were clustered in layer 2, most of which were supposed to be presubicular pyramidal cells. In the parasubiculum, th e overall immunostaining pattern of PV and calbindin were somewhat com plementary, In the transition area calbindin-IR neurons were clustered but few PV-IR neurons were located, and thus the distribution of immu noreactive neuronal somata was apparently different from the adjacent parts of the parasubiculum, indicating that the transition area might be a separate entity. In addition to calbindin-IR presumable principal neurons, calbindin-IR and PV-IR nonpyramidal cells were scattered thr oughout the subicular complex, Furthermore, these two calcium binding proteins were colocalized in some nonpyramidal cells in the subicular complex. The present study revealed some new aspects of the areal and laminar organization of the subicular complex, which had not been show n by previous classical purely morphological approaches.