THE NO CGMP PATHWAY AND THE DEVELOPMENT OF NEURAL NETWORKS IN POSTEMBRYONIC LOBSTERS/

The nitric oxide/cyclic 3',5'-guanosine monophosphate (NO/cGMP) signal ing pathway has been implicated in certain forms of developmental and adult neuronal plasticity. Here we use wholemount immunocytochemistry to identify components of this pathway in the nervous system of postem bryonic lobsters as they develop through metamorphosis. We find that t he synthetic enzyme for NO (nitric oxide synthase, or NOS) and the rec eptor for this transmitter (NO-sensitive soluble guanylate cyclase) ar e broadly distributed in the central nervous system (CNS) at hatching. In the brain, NOS immunoreactivity is intensified during glomerular d evelopment in the olfactory and accessory lobes. Whereas only a few ne urons express NOS in the CNS, many more neurons synthesize cGMP in the presence of NO. NO-sensitive guanylate cyclase activity is a stable f eature of some cells, while in others it is regulated during developme nt. In the stomatogastric nervous system, a subset of neurons become r esponsive to NO at metamorphosis, a time when larval networks are reor ganized into adult motor circuits. cGMP accumulation was occasionally detected in the nucleus of many cells in the CNS, which suggests that cGMP may have a role in transcription. Based on these findings, we con clude that the NO/cGMP signaling pathway may participate in the develo pment of the lobster nervous system. Furthermore, NO may serve as a mo dulatory neurotransmitter for diverse neurons throughout the CNS. (C) 1998 John Wiley & Sons, inc.