Migrating neuroblasts of the rostral migratory stream are putative targets for the action of nitric oxide

It has been demonstrated that the gaseous messenger nitric oxide influences cell proliferation and cell migration, and therefore affects adult neurogenesis in mammals. Here, we investigated the putative targets for this action in the rostral migratory stream of the rat. We used immunocytochemical detection of the beta 1 subunit of the enzyme soluble guanylyl cyclase, which can be activated by nitric oxide. Our results under light and electron microscopy demonstrated that the migrating neuroblasts (type A cells) were beta 1-immunopositive. The astrocytes (type B cells), immature precursors (type C cells) and ependymal cells (type E cells) were beta 1-immunonegative. The neurochemical characterization of the soluble guanylyl cyclase-containing cells confirmed these results. In this regard, the beta 1-containing cells expressed doublecortin, a protein expressed by type A cells, and did not express glial fibrillary acidic protein, which is a marker for type B cells. Injection of 5-bromo-2'-deoxyuridine 2 h before killing demonstrated that proliferating cells did not contain soluble guanylyl cyclase. Finally, we found that beta 1-containing type A cells also expressed the A3 subunit of the cyclic nucleotide-gated ion channels. Altogether, the present results indicate that nitric oxide may influence adult neurogenesis acting on the migrating neuroblasts of the rostral migratory stream. In these cells, nitric oxide may activate the enzyme soluble guanylyl cyclase, triggering the production of the second messenger cGMP. In turn, cGMP might induce the opening of cyclic nucleotide-gated ion channels, which are present in these cells.