Localization of NADPH-Diaphorase and Nitric Oxide Synthase Activity in the Eyestalk of the Crayfish, Procambarus clarkii

Abstract

Localization of NADPH-diaphorase and nitric oxide synthase activity in the eyestalk of the crayfish, Procambarus clarkii. Zoological Studies 41(3): 244-250. The distribution of nitric oxide synthase (NOS) in the eyestalk tissues of the crayfish, Procambarus clarkii, was studied using NADPH-diaphorase (NADPH-d) histo-chemistry and an NOS biochemical assay. In the retina, NADPH-d activity was detected in the rhabdom of the ommatidium and axons of retinular cells that terminate in the lamina ganglionaris. In the eyestalk ganglia, NADPH-d was localized to the fibers in the 1st chiasma that connect the lamina ganglionaris and medulla exter-na, and 2 prominent fiber tracts that appear to originate from the medulla terminalis, project distally, and termi-nate in the synaptic layers of the medulla interna. In addition, NADPH-d-positive somata were found in the periphery of the medulla externa. Specific staining of NADPH-d activity was eliminated by DPIP, an inhibitor of NOS-associated NADPH-d. The distribution pattern of NADPH-d activity described above is much broader than that of NOS-immunoreactivity reported in a previous study (Lee et al. 2000). Biochemical analysis revealed that the regions (the medulla interna and medulla terminalis) where only NADPH-d activity (but not NOS-immunoreactivity) was detected also contained significant levels of NOS activity, suggesting that the observed NADPH-d activity is associated with NOS. The combined results indicate that, in contrast to a highly restricted pattern suggested by immunohistochemical data, NOS is widely distributed in the crayfish eyestalk and implicates NO in the processing of visual information.