EXPRESSION OF NOS, PSA-N-CAM AND S100 PROTEIN IN THE GRANULE CELL-MIGRATION PATHWAY OF THE ADULT GUINEA-PIG FOREBRAIN

To investigate the possible role of nitric oxide (NO) in adult neuroge nesis and neuron-glial migration in the rostral migratory stream (RMS) , we used a double-labeled immunofluorescence technique together with confocal laser scanning microscopy, and examined the localization of n itric oxide synthase (NOS), the highly polysialylated isoform of neura l cell adhesion molecule (PSA-N-CAM), and the astroglial marker in bra in, S100 protein (S100), throughout the length of the subependymal lay er (SEL) to olfactory bulb (OB) pathway of the adult guinea pig forebr ain. Blast-like, beaded, clustered immature cellular elements stained for PSA-N-CAM and those having a typical astrocytic phenotypes positiv e for S100 protein were densely interlaced throughout the entire lengt h of the SEL. Some S100 positive ependymoglial cells (tanycytes) gave off their basal projections into the closely packed PSA-N-CAM immunopo sitive clusters in the rostral extension of the subependymal zone (SEZ re). The SEL was devoid of NOS immunoreactivity. A dense network of pu nctate, fenestrated and radially oriented immature cellular elements p ositive both for NOS and PSA-N-CAM intermingled and overlapped in the inner part of the internal granular layer (IGr), whereas in the outer past, PSA-N-CAM expression gradually diminished and the cells shifted to mature bipolar, spherical or spindle-shaped granule cells with unif orm cellular contours, which were exclusively immunopositive for NOS. Radially oriented astroglial phenotypes were intertwined with PSA-N-CA M neuronal clusters in the SEL, and were closely apposed to NOS neuron al elements in the IGr. In summary, these results showed a distinct se paration of neurons and glia as revealed by PSA-N-CAM and S100 protein immunostaining, and an inverse spatio-temporal correlation of express ion between PSA-N-CAM (immature neuroblasts) and NOS (mature neurons) in the adult guinea pig RMS. (C) 1998 Elsevier Science B.V.