Increase in the Level of Orexin Receptor 1 (OX1R) mRNA in the Brain Structures of Rats Prone to Impulsivity in Behavior

Abstract—

Orexin and its receptors (OXR) are involved in the mechanisms of pathological craving for alcohol and psychoactive drugs. The orexin system is also involved in the mechanisms of non-chemical forms of addiction: binge eating and gambling. The aim of this study was to investigate the level of orexin receptor mRNA in the hypothalamus, hippocampus, and prefrontal cortex of rats prone to impulsivity in behavior in a model for studying the elements of gambling addiction (a variant of the Iowa Gambling Task test). Brain structures were isolated on the 22nd day of the experiment. The OX1R gene expression was higher in the hypothalamus by 122% and in the hippocampus—by 149% in rats preferring to receive a high reward, but with a low probability as compared with a group of animals that preferred a low level of reinforcement, but with a 100% probability. On the contrary, no significant changes were observed in the level of OX1R mRNA in the prefrontal cortex. The level of OX2R mRNA insignificantly changed in the hypothalamus, hippocampus, and prefrontal cortex of rats prone to impulsivity in behavior. The data obtained suggest involvement of OX1R in the hypothalamus and hippocampus in the mechanisms mediating impulsive behavior and the choice of the significance of positive reinforcement in terms of its varying strength and probability.