A common feature of all drugs with addiction liability is their ability to activate the mesolimbic brain reward pathway and increase dopamine levels in the nucleus accumbens (9). This can occur by facilitation of dopamine release from presynaptic neurons or inhibition of its reuptake (such as cocaine and amphetamines), or by increasing the activity of dopaminergic neurons (such as alcohol, nicotine, opioids and cannabis) (9). While dopamine plays an important role in mediating the rewarding properties of drugs of abuse, other neurotransmitters including serotonin, opioid peptides, γ-aminobutyric acid, acetylcholine, endocannabinoids and glutamate also contribute (9). It is notable that learning processes are crucial to the neurobiology of addiction. In both addicted humans and laboratory animals, drug-associated conditioned stimuli can evoke dopamine release alone.
