Optogenetic stimulation of food intake in mice expressing Channelrhodopsin-2 (ChR2) in Agrp neurons. Pilot experiment with Jon Resch and Brad Lowell in the Promethion indirect calorimeter. Blue shading represents light pulses. X-axis represents clock time (14:00 = 2pm). Mice had free access to food and were made hungry by activating this neuronal population. Food intake increased, metabolic rate (VO2) increased, body temperature increased, and increased physical activity in mice that would normally be sleeping.