Immunohistochemical and enzyme histochemical characteristics of short axon cells in the olfactory bulb of the golden hamster.

Short axon (SA) cells in the olfactory bulb are subdivided into six types after Golgi impregnation, although their functional significance is not fully elucidated. In the present study, we examined the golden hamster olfactory bulb by immunohistochemistry to localize neurotransmitters, neuron-specific marker, and nitric oxide synthase (NOS) in the SA cells. Enzyme histochemical staining was also performed to detect the activity of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase, which is identified with NOS. In the main olfactory bulb (MOB), neuropeptide Y (NPY)-, NOS-, and NADPH-diaphorase-positive SA cells were detected in the glomerular layer (GL), vasoactive intestinal polypeptide (VIP)-positive SA cells in the external plexiform layer (EPL), and NPY-, somatostatin (SOM)-, protein gene product 9.5 (PGP 9.5)-, NOS-, and NADPH-diaphorase-positive SA cells in the granule cell layer (GCL). In the accessory olfactory bulb (AOB), VIP- and PGP 9.5-positive SA cells were detected in the mitral/tufted cell layer (MTL), and NPY-, SOM-, NOS-, and NADPH-diaphorase-positive SA cells in the GCL. The common presence of NPY- SOM-, VIP-, PGP 9.5-, NOS-, and NADPH-diaphorase-positive SA cells in both the MOB and the AOB may suggest that respective types of cells with the same immunoreactivity play the same role no matter where these cells are located in the MOB or the AOB.