Diversity of the calretinin immunoreactivity in the dentate gyrus of gerbils, hamsters, guinea pigs, and laboratory shrews

We have recently reported that calretinin (CR) immunoreactivity in the mous e dentate gyrus (DG) is prominently different from that in the rat and monk ey dentate gyrus. The CR-immunoreactive (IR) neuronal components characteri stic of mouse DG were (1) mossy cells in the ventral hilus, (2) punctate el ements in the inner molecular layer, (3) Cajal-Retzius cells in the molecul ar layer, and (4) immature granule cells at the basal part of the granule c ell layer, which were also IR for highly polysialylated neural cell adhesio n molecule. In this study, we examine the CR-IR elements in the DG of the g erbil, hamster, guinea pig, and laboratory shrew, and compare them with tho se of the rat, monkey, and mouse, reported previously. We show that mossy c ells are distributed throughout the dorsoventral axis in all these animals, but mossy cells in the ventral hilus of the hamster, gerbil, and laborator y shrew are CR-IR, resembling those of the mouse, whereas mossy cells of th e guinea pig are CR negative, like those of the rat. The inner molecular la yer, the target zone of mossy cells, was observed to contain CR-IR punctae in the hamster, gerbil, and laboratory shrew, which corresponds to the CR i mmunoreactivity of the mossy cells. In addition, we observed CR-IR presumed Cajal-Retzius cells in all animals examined. On the other hand, CR-IR imma ture granule cells were encountered in the laboratory shrew, but not in oth er animals. The present study reveals prominent species differences in the CR-IR elements of the DG. (C) 1999 Wiley-Liss, Inc.