Rapid Antidepressant Improvement Secondary to Excitatory Brain Responses

Buprenorphine is a μ-opioid partial agonist and kappa-opioid antagonist that is used to treat moderate to severe pain and opioid dependence. The intramuscular administered opioid agonist which will be used to modulate reward learning signals to understand placebo effects in patients with depression. In the buprenorphine condition, participants will receive one IM injection of 0.3mg/1ML buprenorphine hydrochloride (Buprenex®. Richmond, VA: Reckitt Benckiser Pharmaceuticals Inc.; 2006) (onset of action: ≥15 minutes; peak effect: \~1 hour; duration: \~6 hours) and an oral placebo tablet.

Naltrexone is thought to strongly block μ-opioid receptors. Oral (pill) opioid antagonist which will be used to modulate reward learning signals to understand placebo effects in participants with depression. In the naltrexone condition, participants will receive one tablet of 50mg Naltrexone hydrochloride (ReVia®. Toronto, ON: Teva Canada Limited; 2015) (onset of action: ≥15 minutes; peak effect: \~1 hour; duration: \~24 hours) and a saline IM injection.

Oral placebo: to match the oral naltrexone.

IM saline placebo: to match the i.v. buprenorphine.

Participants will receive two blocks of each TBS form. During the first block, stimulation intensity will be gradually escalated in 5% increments (from 80% to 110% rMT) in order to enhance tolerability. In all conditions, the investigators will apply 600 pulses of theta burst at 110% RMT. Each block of iTBS will consist of 20 trains, each lasting 2s with intertrain intervals of 8s, for a total of 192s. Each block of cTBS will consist of one continuous train of 40s. The sTBS will make use of two surface electrodes placed on the scalp.