Auditory cortical stimulus processing in major depression: effects of noradrenergic versus serotonergic agents

Aims: The loudness dependence of auditory evoked potentials (LD) has been suggested as a marker of central monoaminergic function. A strong LD is associated with a reduction of central serotonergic activity and a favorable response to serotonergic agents in patients with depression. In combined neurophysiological and nuclear imaging studies the LD was correlated with both central serotonin and dopamine transporter availability. Aim of this study was to investigate the long-term effects of serotonergic versus noradrenergic antidepressants on LD in patients with depression. Methods: Patients with major depressive episodes were included into a 4-week treatment study with either the noradrenergic antidepressant reboxetine (reb) or the serotonergic agent citalopram (cit). Neurophysiological and clinical assessments (HAM-D scores) were performed both at baseline and under medication. Results: 90 patients [44 cit, 46 reb] were prospectively investigated. Baseline-LD and -HAM-D scores did not differ significantly between the groups. Under medication there was no significant change in LD in neither group, nor were there significant differences between the groups. Conclusion: Serotonergic or noradrenergic medication do not seem to significantly or differentially alter the LD in depressed patients. Implications of these results regarding central monoaminergic function both at baseline and under treatment will be discussed.