NADPH-DIAPHORASE HISTOCHEMISTRY REVEALS HETEROGENEITY IN THE DISTRIBUTION OF NITRIC-OXIDE SYNTHASE-EXPRESSING INTERNEURONS BETWEEN OLFACTORY GLOMERULI IN 2 MOUSE STRAINS

The expression of nitric oxide synthase (NOS) in the olfactory bulb wa s compared between two mouse strains, CD-1 and BALB/c, that differ in the connectivity within their olfactory glomeruli, their content of ty rosine hydroxylase, and their response to olfactory deafferentation. L abelled cells were qualitatively and quantitatively analyzed by both i mmunohistochemistry for NOS and histochemistry for nicotinamide adenin e dinucleotide phosphate (NADPH)-diaphorase (ND). Both periglomerular cells and short-axon cells were observed with both techniques employed , and their colocalization in the same neurons demonstrated that ND is a reliable marker for NOS-expressing cells in the mouse olfactory bul b (OB). The histochemical technique differentiates two types of glomer uli: ND-positive and ND-negative, Olfactory glomeruli in the CD-1 stra in were about 7% larger than those in the BALB/c animals. While the de nsity of NOS/ND-containing periglomerular cells was similar between bo th strains studied, more NOS/ND-labelled cells were observed in the ND -positive glomeruli (P = 0.002). Since periglomerular cells in the BAL B/c strain do not receive direct olfactory receptors synapses, the pre sent results indicate that such inputs do not regulate the expression of NOS and ND activity in the periglomerular cells, The different dens ities of NOS/ND-expressing periglomerular cells may indicate that nitr ic oxide is implicated in a differential modulation of the odor respon se within both types of chemically distinct glomeruli in the mouse olf actory bulb. J. Neurosci. Res. 53:239-250, 1998. (C) 1998 Wiley-Liss, Inc.