Identification and distribution of nitric oxide synthase in the brain of adult zebrafish

Nitric oxide (NO) is proposed to be involved in developmental and plastic p rocesses. We investigated the presence and distribution of nitric oxide syn thase (NOS) in the zebrafish (Danio rerio) using molecular and histochemica l techniques. A partial gene sequence corresponding to the neuronal NOS iso form (nNOS) was identified, and in situ hybridization revealed cellular nNO S mRNA expression throughout the brain of adult zebrafish, distributed in d istinct central nuclei and in proliferation zones, NOS immunoreactivity and nicotinamide adenine dinucleotide phosphate diaphorase activity partly coi ncided with the nNOS mRNA expression, however was present also in additiona l neuronal and non-neuronal cell types. The results indicate the occurrence of different NOS isoforms in the adult brain, of which nNOS may participat e in neurotransmission, and in mechanisms related to the continuous growth and neuronal plasticity of the teleost brain. (C) 2000 Elsevier Science Ire land Ltd, All rights reserved.