Scientists identify brain circuitry that triggers overeating

Scientists at the University of North Carolina School of Medicine say they identified brain circuitry that triggers overeating. "The study underscores that obesity and other eating disorders have a neurological basis," senior study author Garret Stuber said in a statement. "With further study, we could figure out how to regulate the activity of cells in a specific region of the brain and develop treatments." In the 1950s, scientists electrically stimulated a region of the brain called the lateral hypothalamus. Stuber wanted to focus on one cell type -- gaba neurons in the bed nucleus of the stria terminalis, or BNST. The BNST is an outcropping of the amygdala, the part of the brain associated with emotion. The BNST also forms a bridge between the amygdala and the lateral hypothalamus, the brain region that drives primal functions such as eating, sexual behavior and aggression. The BNST gaba neurons have a cell body and a long strand with branched synapses that transmit electrical signals into the lateral hypothalamus. Stuber's team stimulated those synapses by using an optogenetic technique, an involved process that would let him stimulate BNST cells simply by shining light on their synapses. Typically, brain cells don't respond to light, so Stuber's team used genetically engineered proteins from algae that are sensitive to light and used genetically engineered viruses to deliver them into the brains of mice. Stuber's team then implanted fiber optic cables in the brains of these specially bred mice, and this allowed the researchers to shine light through the cables and onto BNST synapses. As soon as the light hit BNST synapses the mice began to eat voraciously even though they had already been well fed. Moreover, the mice showed a strong preference for high-fat foods, Stuber said. The findings were published in the journal Science.