Distribution of the A3 subunit of the cyclic nucleotide-gated ion channels in the main olfactory bulb of the rat.

Previous data suggest that cyclic GMP (cGMP) signaling can play key roles in the circuitry of the olfactory bulb (OB). Therefore, the expression of cGMP-selective subunits of the cyclic nucleotide-gated ion channels (CNGs) can be expected in this brain region. In the present study, we demonstrate a widespread expression of the cGMP-selective A3 subunit of the cyclic nucleotide-gated ion channels (CNGA3) in the rat OB. CNGA3 appears in principal cells, including mitral cells and internal, medium and external tufted cells. Moreover, it appears in two populations of interneurons, including a subset of periglomerular cells and a group of deep short-axon cells. In addition to neurons, CNGA3-immunoreactivity is found in the ensheathing glia of the olfactory nerve. Finally, an abundant population of CNGA3-containing cells with fusiform morphology and radial processes is found in the inframitral layers. These cells express doublecortin and have a morphology similar to that of the undifferentiated cells that leave the rostral migratory stream and migrate radially through the layers of the OB. Altogether, our results suggest that CNGA3 can play important and different roles in the OB. Channels composed of this subunit can be involved in the processing of the olfactory information taking place in the bulbar circuitry. Moreover, they can be involved in the function of the ensheathing glia and in the radial migration of immature cells through the bulbar layers.