Brain signals when 'Special K' will do the trick

These MEG scans show response to finger stroking pre- and post-ketamine. Courtesy of the National Institutes of Health

Special K is more than just a cereal--it's a party drug, anesthetic and vet med, and it could be an antidepressant, too. Researchers at the NIH's National Institute of Mental Health (NIMH) found a new biomarker, a brain signal, that could help pick out those patients most likely to respond to a single dose of ketamine, known on the street as "Special K," as a short-term treatment for depression.

Treatment for depression, though often effective, can take weeks or months to kick in, and this can be too long for some patients. The anesthetic ketamine has a bad rap as an abused drug, but for some people, including those with major depression or bipolar disorder, a single dose can reverse depression and suicidal feelings in a matter of hours or even minutes, with effects that can last for months.

The researchers mapped brain activity, using magnetoencephalography (MEG), in 20 drug-free people with depression who were at rest or having a finger gently stroked. Readings were taken before and after a single dose of ketamine. After a dose of the drug, the brain activity was the same for people at rest, whether they responded to the drug or not. Stroking a finger triggers excitability in the somatosensory cortex (the part of the brain that registers sensory stimulation) and those people who had the best response to ketamine had an increased MEG response to finger strokes after receiving the drug.

Ketamine hits a different target than most antidepressants. While ketamine's rapid action does give it potential for use in emergency settings, it doesn't work for everyone and the side effects can be pretty tough. There have been other biomarkers found recently by the National Institutes of Health and collaborators that link with ketamine activity in depression, including markers in blood, genetic mutations and a sleep-specific brain wave. Combining these could help doctors tailor treatment to patients and exploit the findings to create safer, faster and more effective drugs.

"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 Dr. Carlos Zarate of the 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."

- read the press release
- see the abstract

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