A possible link between lack of sleep (insomnia) and obesity has been traced to hypocretin/orexin cells in the hypothalamus region of the brain that are easily excited and sensitive to stress, Yale School of Medicine researchers report in the April issue of Cell Metabolism.
"If these neurons are over-activated by environmental or mental stress in daily situations, they may support sustained arousal, triggering sleeplessness, leading to overeating," said lead author Tamas Horvath, associate professor in the Departments of Obstetrics, Gynecology & Reproductive Sciences (Ob/Gyn) and Neurobiology at Yale School of Medicine. "The more stress you have, the lower the threshold becomes for exciting these hypocretin neurons."
Horvath and co-author Xiao-Bing Gao, assistant professor in Ob/Gyn, studied hypocretin/orexin neurons in mice using electrophysiology and electron microscopy. They found a unique, previously un-described organization of inputs on hypocretin neurons in which excitatory nerve junctions outnumber inhibitory contacts by almost 10 fold. Stressors such as fasting further excite these neurons.