NITRIC-OXIDE AND CYCLIC-GMP REGULATE RETINAL PATTERNING IN THE OPTIC LOBE OF DROSOPHILA

The photoreceptors of Drosophila express a nitric oxide-sensitive guan ylate cyclase during the first half of metamorphosis, when postsynapti c elements in the optic robe are being selected. Throughout this perio d, the optic robes show NADPH-diaphorase activity and stain with an an tibody to nitric oxide synthase (NOS). The NOS inhibitor L-NAME, the N O scavenger PTIO, the sGC inhibitor ODQ, and methylene blue, which inh ibits NOS and guanylate cyclase, each caused the disorganization of re tinal projections and extension of photoreceptor axons beyond their no rmal synaptic layers in vitro. The disruptive effects of L-NAME were p revented with the addition of 8-bromo-cGMP. These results suggest NO a nd cGMP act to stabilize retinal growth cones at the start of synaptic assembly.