NITRIC-OXIDE SYNTHASE DISTRIBUTION IN THE GOLDFISH MAUTHNER CELL

NADPH-diaphorase histochemical staining was used to assess the distrib ution of the enzyme nitric oxide synthase (NOS) in the goldfish brain, with the emphasis on the Mauthner (M-) cell, a reticulospinal neuron, and its inputs. Labeling was specific for certain cell types, includi ng the M-cell, which stained heavily. The reaction product in this neu ron was uniformly distributed along its axon, soma, and ventral and la teral dendrites. Afferents which synapse with the M-cell were also NAD PH-diaphorase positive, including an identified class of inhibitory in terneurons and the large myelinated club endings (LMCE) of eighth nerv e fibers. The presence of NADPH-diaphorase in a lower level brainstem circuit that undergoes activity-dependent long-term potentiation of bo th excitatory and inhibitory synapses and is accessible for morpho-fun ctional correlations provides the opportunity to elucidate the mechani sm and role of nitric oxide at the single cell level. (C) 1997 Elsevie r Science Ireland Ltd.