Expression of nitric oxide synthase and soluble guanylyl cyclase in the developing olfactory system of Manduca sexta

The gaseous messenger nitric oxide (NO), with its ability to mediate both i ntercellular and intracellular communication, can play important roles in m ediating cellular communication in both the development and the function of the nervous system. The authors investigated the possible role of NO signa ling in the developing olfactory system (antennal lobe) of the moth Manduca sexta. NO synthase (NOS), the enzyme that generates NO, was localized by u sing immunocytochemistry, in situ hybridization, and nicotinamide adenine d inucleotide phosphate-diaphorase (NADPH-d) histochemistry. Although NADPH-d staining appears to be a poor indicator of the presence of NOS in this sys tem, immunocytochemistry and in situ hybridization reveal that NOS is expre ssed in the axons of olfactory receptor neurons throughout development and in the perineurial sheath that covers. the brain early in development. NOS is present in axon terminals as they form protoglomeruli, raising the possi bility that NO mediates cell-cell interactions during antennal lobe develop ment. NO-sensitive soluble guanylyl cyclase (sGC), one of the best characte rized targets of NO, was localized in the developing olfactory system by us ing in situ hybridization and immunocytochemistry for the Manduca sexta sGC alpha 1 subunit. The ability of the developing olfactory system to respond to exogenous NO also was examined by using cyclic guanosine monophosphate immunocytochemistry. sGC is expressed in mechanosensory neurons in the deve loping antenna and in many antennal lobe neurons in both the medial and lat eral cell body clusters. Thus, NOS and sGC are expressed in a pattern that suggests that this signaling pathway may mediate intercellular communicatio n during development of the olfactory system in Manduca sexta. (C) 2000 Wil ey-Liss, Inc.