Calbindin D-28K and NADPH-diaphorase activity are localized in different populations of periglomerular cells in the rat olfactory bulb.

Calbindin D-28k (CaBP) immunocytochemistry and NADPH-diaphorase (ND) histochemistry have been combined in the rat olfactory bulb by successive incubations of the same sections. The outer strata showed a similar neuronal staining pattern for both markers with positive periglomerular neurons (although the CaBP-stained periglomerular cells were six-fold more abundant than the ND-active ones) and larger neurons scattered in the glomerular and external plexiform layers. Both populations of periglomerular cells were distinct but they did not show specific morphological characteristics nor a predominant distribution around ND-positive and negative glomeruli. The colocalization study demonstrates that the larger ND and CaBP-stained juxtaglomerular cells, identified according to their size, location and processes branching patterns as two types of short axon cells (superficial short-axon and Van Gehuchten Cells) were also independent populations.