Immuno-protective effect of neuropeptide Y immersion on the juvenile tilapia infected by Streptococcus agalactiae.

Neuropeptide Y (NPY), an important neurotransmitter, is widely distributed in the nervous systems of vertebrates. Multiple functions of NPY in mammals include the regulation of brain activity, emotion, stress response, feeding, digestion, metabolism and immune function. In the present study, we used synthetic NPY to immerse juvenile tilapia, thus firstly exploring the dose and time effect of this immersion. The results showed that the expression level of y8b and serum glucose increased after NPY immersion. When juvenile tilapia was challenged with Streptococcus agalactiae (S. agalactiae), no matter before or after the administration of NPY-immersion, it was found that NPY immersion could inhibit the expression of il-1β induced by S. agalactiae in telencephalon, hypothalamus, spleen and head kidney, and then promote the expression of il-10. In addition, NPY-immersion could reduce the activity of serum SOD but increase that of lysozyme, and ameliorate tissue damage in the head kidney and spleen of juvenile tilapia caused by S. agalactiae infection. This study firstly proposes the potential of NPY to be an immune protect factor in juvenile fish, and the results can provide a reference for the application of immersion administration in the immune protection of juvenile fish.