The current investigators have studied the NE reuptake blocking properties of antidepressants in both healthy volunteers and patients with depression using tyramine pressor tests (Turcotte et al., 2001; Gobbi et al., 2003; Blier et al., 2007; Debonnel et al., 2007; Blier et al., 2010). This peripheral model of adrenergic function involves administration of repeated intravenous injections of tyramine and measurement of transient increases in systolic blood pressure (SBP) that occur after a tyramine load. This approach has led to dose-dependent SBP increases that are reliably reproduced one week apart in healthy volunteers who received placebo which supports the use of the tyramine pressor test to assess the functional capacity of different medication regimens to inhibit NE reuptake at steady state levels. Serotonin reuptake has been extensively studied in human participants using the blood platelet model. In this assay, whole blood 5-HT and/or platelet content is determined before and after giving reuptake inhibitors. Since the 5-HT transporter is similar on 5-HT neurons in the brain and on platelets, the degree of 5-HT depletion in the blood can be used as a measure of 5-HT reuptake blockade in the brain. Together, these experimental approaches will identify the potency of levomilnacipran for NE and 5-HT reuptake inhibition.