ABSTRACT
The brain reward pathway, the mesotelencephalic dopaminergic system, from the brain stem (ventral tegmental area) to the nucleus accumbens, is described. The mechanism of the action of this reward pathway is identified. How the various drugs activate this pathway, including opiate drugs (e.g. morphine, heroin and pethidine), cocaine, cannabis, amphetamines, hallucinogens, crystal methamphetamine and others, is explored. The receptors that these drugs bind to as part of their function are identified. Ketamine activity and its effects are discussed. Withdrawal from the drugs, and tolerance of the drugs, is discussed. How drugs of addiction are used in medicine to treat other conditions is explored.
