HISTOCHEMICAL MAPPING OF NADPH DIAPHORASE IN THE NERVOUS-SYSTEM OF THE PARASITIC NEMATODE ASCARIS-SUUM

NADPH diaphorase has recently been discovered to be responsible for ne uronal nitric oxide (NO) synthase activity in mammals. It thus serves as a histochemical marker for the localization of NO synthase in the n ervous system. The histochemical technique was used to map out potenti al NO-producing neurones in the nervous system of the parasitic nemato de, Ascaris suum. Positive staining for NADPH diaphorase was present i n various parts of the central nervous system, in particular within se lective cell bodies and fibres in the ventral ganglion, the retrovesic ular ganglion, ventral and dorsal cords and sublateral lines. Intense staining was also present in the motorneurone commissures, indicating a potential role for NO as a neurotransmitter at the neuromuscular jun ction. NADPH disphorase-positive neurones were not confined to the cen tral nervous system. Selective staining was also present in the enteri c nervous system, in particular the pharynx and in the peripheral nerv ous system innervating the sensory organs.