Weight loss puzzle: Which neurons turn satiety on and off?
In their hunt for a switch in the brain that turns on and off the drive to eat, obesity researchers have come up with a bright idea: They have tried a relatively new technique to activate or suppress certain neurons’ electrical activity - introducing tiny molecular lights called optogenetics into cells’ midst. In mice, at least, the technique has helped identify both the exact brain cells and complex cascade of processes that prompt the dispatch of a “stop eating” signal from the brain to the gut.
The team’s findings, published recently in the journal Nature Neuroscience, underscore that satiety signaling is a far from simple process. When a sensation of fullness — or of distaste or sickness — prompts us to stop eating, that appears to be the orchestrated result of the activation of one class of neurons and the inhibition of a distinct but related class of neurons, all located in the same tiny region.
To make matters even more complex, the region of the brain from which satiety signals are sent forth — the amygdala central nucleus - is a center of emotional processing, specifically of fear and anxiety. So researchers needed to test whether flipping the satiety switch to “on” would also turn on emotional angst or malaise. That’s a key concern for those who will someday use these findings to devise new weight-loss medications.
On that question, at least, the news was good. When scientists “turned the lights on” and activated a unique cluster of cells in the amygdala central nucleus associated with satiety, the effect was not increased anxiety, but calm: In lab tests, mice whose satiety neurons were activated by molecular light were no more likely to show signs of fear than were control mice: They just ate less. A lot less.
Los Angeles Times
Study: Eye color may affect pain tolerance
Pain comes in all shapes and sizes. Whether it arises in the chronic form of arthritis or the sudden squeeze of cardiac arrest, pain is the main motivator for a visit to the hospital.
Doctors may now have to note the eye color of their patients before choosing a procedure to treat them. New research has shown that women with dark — brown and hazel — eyes respond differently to pain than those with light — blue and green - eyes.
During the 2014 annual meeting of the American Pain Society, Inna Belfer, M.D., Ph.D., an associate professor of anesthesiology at the University of Pittsburgh, presented a study possibly linking eye color to variations in pain tolerance.
The study sample consisted of 58 healthy pregnant women at Magee-Womens Hospital of the University of Pittsburgh Medical Center. Twenty-four women were placed in the dark group, and the remaining 34 were placed in the light group. Dr. Belfer and her team measured responses to pain before and after giving birth through a variety of quantitative standard testing, questionnaires and surveys.
The results indicated that women in the dark group experienced more dramatic response to pain with increases in anxiety and sleep disturbances than those in the light group.
“This was a small pilot study to start off,” said Dr. Belfer. “All we know now is super limited — a hypothesis about why there is a difference at this point would be too optimistic — but this could be a next step in finding a genetic background of pain.”
Pittsburgh Post-Gazette
