Two years ago, Zarate and colleagues reported that ketamine, which targets the brain chemical glutamate, can lift depressions in just hours, instead of the weeks it takes conventional antidepressants, which work through the brain chemical serotonin. Evidence suggests that glutamate likely acts closer to the source of the depression than serotonin, and is not dependant on slower mechanisms, such as the synthesis of new neurons.
Earlier imaging studies with conventional antidepressants had hinted that increased activity of the mood-regulating hub, called the anterior cingulate cortex (ACC), signals a better response.
To find out if ACC activity might also forecast response to glutamate-targeting medications, the NIMH researchers imaged the brain activity of 11 depressed patients and 11 healthy participants, using magnetoencephalography (MEG). This imaging technology can non-invasively detect brain electromagnetic activity lasting only milliseconds – the speed of communications in neural circuits – whereas other functional brain imaging techniques can only capture activity that last seconds or minutes, and some involve radiation exposure.
This precise timing enabled the MEG scanner to capture the brain's split-second responses to rapidly flashing pictures of fearful faces, a task known to activate the ACC. While healthy participants' ACC activity dropped off as they quickly habituated to the faces, patients' ACC activity showed an opposite trend. The more robust this increase, the more symptoms improved just four hours after a patient received a single infusion of ketamine.
"The ACC may be slow to respond, but not completely impaired, in patients who respond to ketamine," explained Cornwell.
While ketamine can lift depression very rapidly for some people ketamine does have side effects, especially at higher doses. Don't use it recklessly.
|Share |||Randall Parker, 2008 October 02 11:08 PM Brain Depression|