Calbindin D28k and parvalbumin immunoreactivity in the rabbit superior colliculus: An anatomical study

The expression pattern of two calcium binding proteins (CaBP), calbindin D2 8k (CB) and parvalbumin (PV), in the superior colliculus (SC) of the adult rabbit, as well as the morphology of the immunoreactive cells were examined . The study was performed on 12 rabbits. Coronal sections from postmortem S C were analyzed by light microscopy, and drawings of CaBP-labeled cells wer e obtained using a drawing tube. No previous information is available on ei ther the CB/PV expression or the morphology of CB/PV positive cells in the SC of the adult rabbit. Therefore, in this study we show that CB neurons an d neuropil form three main tiers: the first located within the stratum zona le (SZ) and the upper part of the stratum griseum superficiale (SGS), the s econd located within the stratum griseum intermedium (SGI), and the third, located within the medial and central areas of the stratum griseum profundu m (SGP). In contrast to this layer labeling, almost no CB-positivity is fou nd within the other collicular layers. On the other hand, the densest conce ntration of PV labeled cells and terminals is found within a single dense t ier that spanned the ventral part of the startum griseum superficiale (SGS) and the dorsal part of the stratum opticum (SO). Anti-PV neurons are also scattered through the deeper layers below the dense tier. In contrast, almo st no anti-PV labeled neurons or neuropil are found within the stratum zona le (SZ) and upper SGS. This distribution represents a new pattern of sublam ination in the SC of this species. All the previously described cell types in other mammals are observed in the rabbit SC: marginal cells, horizontal cells, pyriform cells, narrow-field vertical cells, nide-field vertical cel ls, and stellate/mulipolar cells. Detailed drawings of all these cellular t ypes are represented to show their complete morphology. The results of this study indicate that both CB and PV are present in a variety of neurons, wh ich present a number of homologies between mammals, but have a different lo cation and/or distribution, according to the different species. These findi ngs are thus relevant to better understand the organisation of the SC in ma mmals. Anat Rec 259:334-346, 2000. (C) 2000 Wiley-Liss, Inc.