This study uses a double-blind, placebo-controlled, randomised between-groups design to test if administration of a serotonin receptor subtype 4 (5HT4) agonist called PF-04995274 has positive effects on emotional processing and neural activity in unmedicated depressed patients. Participants are patients who fulfill criteria for current episode of Major Depressive Disorder (MDD), and they will be randomised to receive 7 days treatment with either PF-04995274 (15 mg daily), citalopram (20 mg daily) or a matched placebo. Participants will come for a Screening Visit, a First Dose Visit, Research Visit One (including MRI scan) and Research Visit Two (including measures of emotional processing and non-emotion cognition).
This study will test whether seven days administration of a serotonin receptor subtype 4 (5HT4) agonist called PF-04995274 has positive effects on cognition, emotional processing and neural activity in unmedicated depressed patients compared to placebo. The study will also include a group of patients randomised to seven days administration of citalopram (20 mg), which is a standard treatment for depression.