Ketamine has been used as a tranquilizer, club drug, and anesthetic. New studies show that it also acts as a rapid antidepressant. A single dose can work in as little as half an hour. Normally, antidepressants take several weeks to work. In the video, Morgan discusses its great potential.
Summary of the Paper
This paper examines how ketamine works to rapidly reduce depression. Ketamine targets a part of the brain called the ‘lateral habenula.’ This small area acts as the anti-reward center. For example, a rat pushes a lever expecting a treat and does not receive a treat. The lateral habenula will reduce the activities of the reward centers. Then, the rat will be less likely to push the level in the future.
In depressed patients, the lateral habenula fires in rapid bursts instead of slow waves. This causes many symptoms, including dispair and anhedonia. Despair is the feeling of hopelessness. Anhedonia is the loss of pleasure. Two types of receptors must be activated for bursting in the lateral habenula to occur and ketamine blocks one of them.
How do you measure depression in a rat?
- Despair is measured by the forced swim test. Rats are put in an inescapable environment filled with water. This is typically an acrylic box. Then, researchers see if they try to escape. Depressed rats lose hope to escape the stressful environment and just float there.
- Anhedonia is measured by the sucrose (sugar) preference test. Mice with anhedonia do not prefer sugar water to plain water.
Yang, Yan, et al. “Ketamine blocks bursting in the lateral habenula to rapidly relieve depression.” Nature 554.7692 (2018): 317.