[Molecular mechanisms of the brain reward system].

The brain possesses a reward system which produces positive emotion. To reveal the mechanisms of the brain reward system, investigation of mechanisms underlying actions of substances of abuse can be one of the promising research approaches. Various behavioral tests using animals and methods in genomic science are also useful for these studies. I introduce our findings obtained by these ideas and techniques as follows: (i) Inhibition of methamphetamine preference by G-protein activated inwardly rectifying potassium (GIRK) channel inhibitors. (ii) Essential role of NMDA receptor channel GluN2D subunit in phencyclidine effects on animal behavior. (iii) Association of polymorphisms in the mu-opioid receptor and GIRK genes with opioid sensitivity.