Orexins and the brain reinforcing systems

Abstract

The purpose of the review was to analyze the neurochemical and neurophysiological mechanisms of the orexin system and the role of orexin in body functions and behavior. The focus is on the participation of orexin in the mechanisms of reinforcement and the formation of addictive behavior. At the beginning of the review a history of the first works on the field of orexin and its receptors are described. Hypothalamic orexin-producing cells and effects on brain functions are described. The effects of orexins and their receptors on eating behavior, wakefulness and positive reinforcement are described. Then, the effects of orexins on narcolepsy was analyzed. The participation of orexins in the mechanisms of reinforcement and dependence and the key role of orexins in the development of addictive behaviors is described. The special role of orexin in the formation of ethanol dependence is shown. Next, the issue of the action of orexins under stress was considered. Orexins have been shown to play an important role in the regulation of the nervous and humoral mechanisms mediating the formation of emotional memory associated with negative experience. It is concluded that orexin can modulate the estimation of stress and probability for reaching stimulus. In this regard, orexin antagonists can be considered as possible promising means of preventing and treating disorders of the anxiety-phobic spectrum, as well as disorders associated with the use of addictive drugs caused by stress and environmental stimuli.