DVS is the main metabolite of the antidepressant/anxiolytic medication Venlafaxine (Effexor). Like parent compound, DVS is an antidepressant inhibiting both serotonin (5-HT) and norepinephrine (NE) reuptake. However, no studies to date describe the in vivo potency of this drug on monoamines reuptake. Consequently, it appears essential to determine the potency of DVS in human subjects using a wide dose range in order to determine at which dose(s) it starts inhibiting 5-HT and NE reuptake. The investigators are interested in learning whether there is a gender difference in the dose of the study medication at which NE reuptake inhibition occurs.