Nitric oxide synthase activity and immunoreactivity in the crayfish Procambarus clarkii

The presence, characteristics and localization of nitric oxide synthase (NO S) in the eyestalk ganglia of the crayfish (Procambarus clarkii) were inves tigated. Biochemical assay indicated that NOS activity was significantly in hibited by N-G-nitro-L-arginine (a NOS inhibitor), fluphenazine-N-2-chloroe thane (a calmodulin inhibitor) as well as by omitting beta-NADPH or Ca2+ fr om the incubations. Immunohistochemical studies localized NOS immunoreactiv ity (IR) to the first chiasma and the sinus gland. Finally, a NOS-immunorea ctive protein (138 kDa) was detected by Western blot analysis. These data d emonstrate for the first time the existence in crustacean eyestalk ganglia of NOS with biochemical characteristics similar to mammalian constitutive N OS. The localization of NOS-IR suggests that NO may be involved in regulati ng visual processes and neuroendocrine function in crustaceans. NeuroReport 11:1273-1276 (C) 2000 Lippincott Williams & Wilkins.