Brain monoamines and antidepressant-like responses in MRL/MpJ versus C57BL/6J mice

► MRL mice showed high tissue levels of serotonin and dopamine than C57BL/6 mice. ► 5-HT synthesis, transporter density and release were also higher in MRL mice. ► MRL showed larger behavioral responses to acute antidepressants. ► Higher serotonin tone contributed to greater antidepressant responses in MRL mice.