Temporal and spatial pattern of expression of cyclic nucleotide-gated channels in developing rat visual cortex

Cyclic nucleotide gated channels, ligand gated and highly permeable to calc ium, are good candidates for transducing signals received by migrating cell s, growth cones and developing synapses. The level of calcium in growth con es is important for axon guidance. Further, cyclic nucleotides, whose level s can be altered by nitric oxide and other transmitters, are known to alter growth cone motility. We use rat visual cortex as a model in our semi quan titative RT-PCR and in situ hybridization studies to determine the developm ental time course and localization of all three CNG family members (rod, ol factory and cone/testis). We demonstrate that in the cortex, the three chan nel subtypes are each expressed in a distinct temporal and spatial pattern in only sensorimotor and occipital regions of the cortex. Specifically, the rod and olfactory subtypes are present at the time of migration and rapid dendritic outgrowth, and the cone/testis subtype is highly expressed after eye opening. These results suggest CNG channels may play a role in both ear ly and late events in visual cortical development.