For example, there is a null mutation model of depression in zebrafish in which modification of the glucocorticoid receptor gene produces depression-like decreases in locomotion, and this can be alleviated with both anxiolytic/antidepressant selective serotonin reuptake inhibitors (SSRI), like fluoxetine, or a sedative anxiolytic drug like diazepam30. This evidence concerns the gene NR3C1 and major depressive disorder.