[Controlling sleep/wakefulness using optogenetics].

Optogenetics is a recently developed experimental technique to control the activity of neurons using light. Optogenetics shows its power to reveal the physiological role of specific neural circuits in the brain. In particular, manipulation of a specific type of neurons using optogenetics with high accuracy timing enables us to analyze causality between neural activity and initiation of animal behaviors. However, to manipulate the activity of specific neurons in vivo, there are two critical steps to succeed in manipulation of the neural activity and control of the behavior of individual animals. The first step is an adequate number of molecules of light-activated protein that has to be expressed in the cell membrane of the neurons of interest. The second step is the optical system to illuminate the targeted neurons with enough intensity of light to activate the light-activated protein. We applied optogenetics to hypothalamic peptidergic neurons such as orexin/hypocretin neurons or melanin concentrating hormone (MCH) neurons. These neurons are implicated in sleep/wakefulness regulation. In this mini review, I will show the regulatory mechanism of sleep/wakefulness by these neurons using optogenetics.