Nitric oxide in the amphibian (Ambystoma tigrinum) lateral line.

Nicotinamide adenine dinucleotide phosphate reduced-diaphorase (NADPH-d) histochemistry was investigated in the axolotl (Ambystoma tigrinum) lateral line. Hair cells of neuromast organs of the head skin and neurons of the postotic ganglia showed a significant NADPH-d reaction. Multiunit recording of neuromast afferent activity was also performed. Nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) produced an initial slight excitation followed by a significant inhibition of the resting discharge of neuromast afferent neurons. In contrast N(G)-nitro-L-arginine (L-NOARG) produced non-significant actions on the afferent neurons discharge. These findings suggest that afferent neurons and hair cells of the lateral line produce nitric oxide that plays an active role in the mechanisms sustaining basal spike discharge in afferent neurons.