NADPH-DIAPHORASE HISTOCHEMISTRY AND NITRIC-OXIDE SYNTHASE ACTIVITY IN DEUTOCEREBRUM OF THE CRAYFISH, PACIFASTACUS-LENIUSCULUS (CRUSTACEA, DECAPODA)

The activity of an nitric oxide synthase in the deutocerebrum of the crayfish Pacifastacus leniusculus was investigated with histochemical and biochemical methods. By using the NADPH-diaphorase histochemical reaction, known as a selective marker for NO synthase in mammals, it was possible to localize specific neuronal elements in the crayfish. Pronounced diaphorase-staining was observed in peripheral olfactory sensory cells and in the neuropil of the olfactory lobes. Less intense diaphorase-staining also occured in other deutocerebral neuropils, such as the accessory lobes, the lateral antennular neuropil and in the deutocerebral commissure neuropil. The biochemical assay revealed a calcium/calmodulin-dependent formation of citrulline from L-arginine in brain homogenate. It was also possible to show that the selective NO synthase inhibitor L-NOARG decreased the formation of citrulline. These data indicate a role for NO as an intercellular messenger in the crayfish.