Brain signal ID’s responders to fast-acting antidepressant (Part I) | WPN World People News

Scientists have discovered a biological marker that may help to identify which depressed patients will respond to an experimental, rapid-acting antidepressant. The brain signal, detectable by noninvasive imaging, also holds clues to the agent’s underlying mechanism, which are vital for drug development, say National Institutes of Health researchers.

Dr. Zarate views subject in MEG scanner from scanner control room.

The signal is among the latest of several such markers, including factors detectable in blood, genetic markers, and a sleep-specific brain wave, recently uncovered by the NIH team and grantee collaborators. They illuminate the workings of the agent, called ketamine, and may hold promise for more personalized treatment.

"These clues help focus the search for the molecular targets of a future generation of medications that will lift depression within hours instead of weeks," explained Carlos Zarate, M.D., of the NIH’s National Institute of Mental Health (NIMH). "The more precisely we understand how this mechanism works, the more narrowly treatment can be targeted to achieve rapid antidepressant effects and avoid undesirable side effects."

Zarate, Brian Cornwell, Ph.D., and NIMH colleagues report on their brain imaging study online in the journal Biological Psychiatry.

Previous research had shown that ketamine can lift symptoms of depression within hours in many patients. But side effects hamper its use as a first-line medication. So researchers are studying its mechanism of action in hopes of developing a safer agent that works similarly.

Ketamine works through a different brain chemical system than conventional antidepressants. It initially blocks a protein on brain neurons, called the NMDA receptor, to which the chemical messenger glutamate binds. However, it is not known if the drug’s rapid antidepressant effects are a direct result of this blockage or of downstream effects triggered by the blockage, as suggested by animal studies.

To tease apart ketamine's workings, the NIMH team imaged depressed patients’ brain electrical activity with magnetoencephalography (MEG). They monitored spontaneous activity while subjects were at rest, and activity evoked by gentle stimulation of a finger, before and 6.5 hours after an infusion of ketamine.

source: U.S. National Institutes of Health