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Dr. Bob is Robert Hsiung, MD,
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Posted by djmmm on May 20, 2002, at 13:54:35
Low Mu-Opioid Receptor Binding Linked to Response to Emotional Stimulus
NEW YORK (Reuters Health) May 14 - New research suggests that low levels of mu-opioid receptor binding in the limbic system are associated with a stronger than normal response to emotional stimulation.
According to investigators from the University of Michigan at Ann Arbor, this finding may explain the mechanism underlying such psychiatric conditions as posttraumatic stress disorder (PTSD) and depression, and could lead to new pharmacologic approaches to treat these disorders.Dr. Israel Liberzon and colleagues describe in the May 14th issue of the Proceedings of the National Academy of Sciences a "marriage" of two techniques, both using positron emission tomography. To estimate regional cerebral blood flow, they assessed emission scans after intravenous injection of radioactive water. For mu-opioid receptor binding, they injected the radioactive ligand carfentanil and measured its uptake.
Dr. Liberzon's group first measured regional blood flow in 12 healthy male volunteers. They then measured mu-opioid receptor binding as the men were shown images from the standardized international affective picture system. These included aversive images, such as facial mutation, wounds, and dead bodies, while neutral images included faces with neutral expressions and benign scenes. Blank images consisted of a fixation mark on a field of gray.
There was a significant negative correlation between mu-opioid receptor availability in the inferior temporal pole at baseline and cerebral blood flow during the aversive and the nonaversive stimuli.
"This methodology delineates potential neurochemical mechanisms involved in the regulation of mood and activation of regions in the brain," Dr. Liberzon told Reuters Health. "Studying these mechanisms will be important in understanding how dysregulation of emotional responses can occur in psychiatric disorders."
He noted that "we find abnormal activity in PTSD in the same brain region in which we find this relationship between the mu-opioid system and activation in response to emotional stimuli." He speculated that PTSD might also involve abnormalities in the mu-opioid system.
Posted by Elizabeth on May 22, 2002, at 18:02:55
In reply to Opioid Receptors and depression (Elizabeth), posted by djmmm on May 20, 2002, at 13:54:35
That's interesting, but it doesn't seem to say anything about depression. Posttraumatic stress is an anxiety disorder and is quite different from depression, IMO, although most people who have PTSD seem to be diagnosed with depression also (one way to get an idea of what "depression" means in the case of a particular individual is to look at comorbidity). PTSD can make people more likely to overreact emotionally, easily startled, irritable, etc. Based on the information in this article, I'd expect a person suffering from PTSD to be calmed by morphine (not surprising). What's curious is that morphine can also restore emotional responsiveness to a seriously depressed person. These seem to be opposite effects, but maybe I'm looking at it from the wrong angle.
-elizabeth
Posted by Zo on May 24, 2002, at 17:27:35
In reply to Re: Opioid Receptors and posttraumatic stress » djmmm, posted by Elizabeth on May 22, 2002, at 18:02:55
I don't think it's the wrong angle, I just think we are all still groping in the very primitive dark regarding brain chemistry and mood. These are all stabs at making sense, but that's all they are; this is a science in its infancy. . .which is the primary argument for polypharmacy, for tweaking of agents---as opposed to pdocs who say, Here, take this, and at this dose, my god what a waste---and for becoming a very knowledgeable patient!
Zo
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