Siamese fighting fish
A psychology study used male Siamese fighting fish to investigate the effects of fluoxetine, an SSRI used primarily as an antidepressant in humans. Siamese fighting fish were selected as prime models due to having comparable serotonin transporter pathways, which accounts for their aggression. It was found that when exposed to fluoxetine, male Siamese fighting fish exhibited less aggressive behaviour than is characteristic of their species. Similarly, research has found that bettas are responsive to serotonin, dopamine, and GABA.