The role of nitric oxide and neuronal nitric oxide synthase in zebrafish (Danio rerio) shoaling

Nitric oxide (NO)—the product of arginine metabolism catalyzed by nitric oxide synthases (NOS)—is a well-known neurotransmitter which plays an important role in metabolism and amino acid transportation in the nervous system. In particular, it can inhibit monoamine neurotransmitter transportation which affects animal behavior, especially social behavior. Shoaling—is a one kind of social behavior. It is a behavior that individual fish choose to join with their group within two factors; food and predation risk. Shoaling fish has quickly responded to predator and increased the change in feeding competition. In addition, shoaling also effect to stress response on stock density of aquaculture system. The effect of NO molecular signaling on the dopamine pathway was investigated using zebrafish (Danio rerio) as a model organism. Our aim was to understand the role of NOS and NO in shoaling behavior, which is typical of zebrafish. The concentration of NO in the zebrafish brain was modulated using a knockout for the neuronal NOS gene, and NO production was induced through treatment with L-arginine. The existence of NO in the zebrafish brain was confirmed by using a fluorescent probe. Dopamine concentration in the brain was measured by UPLC tandem mass spectrometer. We measured shoaling cohesion of all individual fish of D. rerio, using average distance between all pairs of fish (nearest neighbor distance) and analyzed tracking by Zebralab ViewPoint software. Collectively, our results suggest that a lower level of NO was associated with a higher level of dopamine, which in turn leads to the shoaling behavior.