Viral vectors as probes to decipher brain circuitry for weight control

Multidisciplinary research has recently identified an intrinsic appetite-re gulating network (ARN) in the hypothalamus. The idea that viruses could hel p to chart this complex network has gained impetus owing to a combination o f our improved understanding of virology and of genetic engineering. Recent ly, three groups have employed viral vectors as probes to: (1) trace the in flow of sensory information from the neocortex and limbic systems to the AR N; (2) trace the outflow of information from the ARN to the sympathetic ner vous system to monitor adiposity and energy expenditure; and (3) decipher t he mechanisms underlying leptin resistance, which is responsible for enviro nmentally based obesity.