SLC22A3 and major depressive disorder: In addition, studies using animal models of depression demonstrated antidepressant effects of both pharmacological [34] and antisense blockade [35] of OCT3. As treatment-resistant depression continues to present a significant clinical problem [36], and there is an ongoing search for new antidepressant drugs, these data support the notion of OCT3 as a potential new antidepressant therapy target [31, 37].