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Vol. 342 ,
The iconic 125-year-old Lick Observatory on Mount Hamilton near San Jose, California, is facing the threat of closure...
Recent results from the Curiosity Mars rover have helped scientists formulate a plan for the next phase of its mission...
A new, remarkably powerful drug that cripples the hepatitis C virus (HCV) came to market last week, but it sells for $...
In pretoothbrush populations, gumlines would often be marred by a thick, visible crust of calcium phosphate, food...
Evolutionary biologists have long studied how the Mexican tetra, a drab fish that lives in rivers and creeks but has...
Victorian astronomers spent countless hours laboriously charting the positions of stars in the sky. Such sky mapping,...
In an ambitious project to study 1000 years of sickness and health, researchers are excavating the graveyard of the now...
Stefan Behnisch has won awards for designing science labs and other buildings that are smart, sustainable, and...
- 12 December 2013 1:00 pm , Vol. 342 , #6164
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How to Stop the Munchies
22 December 2005 (All day)
Marijuana has a reputation for making people dash to the kitchen (or the nearest convenience store). New research shows why and helps explain how a hormone called leptin usually keeps the appetite under control. The results may help scientists design better diet drugs.
Researchers have known for several years that a connection exists between leptin and cannabinoids, the molecules in the brain that stimulate appetite and that are related to those found in marijuana (ScienceNOW, April 11 2001). Mice that don't make leptin have oversized appetites, for example, and they have unusually high concentrations of cannabinoids in the hypothalamus. But no one knew how leptin and cannabinoids interacted in the brain.
To examine the relation, Young-Hwan Jo, now at the Albert Einstein College of Medicine, New York City, and colleagues, took a look at slices of mouse hypothalamus. When the team dropped a cannabinoidlike compound onto the neurons, the neurons fired. If the researchers added leptin first, the neurons did not activate.
Both compounds seem to be exerting their influence via calcium ions. Cannabinoids increase calcium in the cell by opening pores, allowing the ion to enter the cell. So the researchers repeated their experiments while measuring calcium inside the activated neurons. Leptin stopped the pores from opening and thus prevented an influx of calcium. Separate experiments revealed that the brains of mice who don't make leptin have greater cannabinoid-induced influx of calcium into hypothalamic neurons than do the brains of mice who make leptin. Because cells require calcium to make cannabinoids, leptin helps keep appetite in check by making sure there aren't too many cannabinoids in the brain, the team reports 22 December in Neuron.
"This is a very important paper," says endocrinologist Uberto Pagotto of the Centro di Ricerca Biomedica Applicata, Sant Orsola-Malpighi Hospital, Bologna, Italy, who notes that the findings may help researchers develop better therapies for obesity.