Ketamine has been used as a horse tranquilizer, infant anesthetic, recreational drug, and most recently, a surprisingly effective treatment for depression (which the US Food and Drug Administration approved last month). Now researchers are starting to understand how ketamine works: by rebuilding connections between neurons lost during stress.
In a new study, researchers took a close-up gander at neurons in live mice under chronic stress, a condition that models depression in rodents. They found that a dose of ketamine helped first restore electrical activity and then rebuild physical connections between neurons that were lost during stress (Science 2019, DOI: 10.1126/science.aat8078). The observations suggest ketamine has both immediate and more sustained effects on how neurons function in the brain.
Neuroscientist Conor Liston at Weill Cornell Medicine and his colleagues implanted a prism into the frontal region of the rodents' brains that, combined with a specialized microscope that captures images at extremely high resolution, allowed them to observe branches of nerve cells called dendrites in great detail over several weeks. They could even see tiny nubbins on the dendrites called spines, which form the synapses connecting nerve cells.
Image: Public Domain, Link