What nemo’s father say a fish can breathe out here fish use this organ system to

A fish breathes by taking water into its mouth and forcing it out through the gill passages. As water passes over the thin walls of the gills, dissolved oxygen moves into the blood and travels to the fish's cells.

dopamine..

"it was found that some people who were taking the drug l-dopa to raise their levels of dopamine were developing schizophrenic-like symptoms supporting research a strength of the dopamine hypothesis is that there are many studies which have shown support for the neurochemical explanation."