Alpha-Amino-3-Hydroxy-5-Methyl-4- Isoxazole Propionic Acid Receptor Components of the Anti-Depressant Ketamine Response

This study is investigating how ketamine relieves severe, treatment-resistant depression — specifically looking at whether AMPA receptors (a type of brain signaling pathway) play a key role in its rapid antidepressant effect. **You may be eligible if...** - You are right-handed (required for brain scan accuracy) - You currently have depression with a Hamilton score above 17 - You have treatment-resistant depression (failed at least one antidepressant) - You are 18 or older **You may NOT be eligible if...** - You have a history of psychosis, bipolar disorder, or substance use disorder - You have significant heart, brain, or neurological conditions - You are pregnant or breastfeeding - You are currently taking medications that interact with ketamine Talk to your doctor to see if this trial is right for you.