Overview: biological processes relevant to drugs of dependence.

Key points are highlighted from five papers that address biological processes underlying the actions of opiates, CNS stimulants, nicotine, alcohol, and benzodiazepines. It is noteworthy that: (1) positive and negative reinforcement are common processes underlying actions of drugs of dependence; (2) dopaminergic systems in the ventral tegmental area of the brain seem to be involved in the positive reinforcement of drugs of dependence; (3) GABA also may be involved in this positive reinforcement; (4) receptor sensitization and desensitization may be involved in the actions of drugs of dependence; (5) noradrenalin, 5-HT, ACh, NMDA and corticosteroids also may be involved in drug dependence; (6) motivational systems and processes in addition to positive and negative reinforcement deserve increased research attention; and (7) there may be genetic-based individual differences in drug dependence processes.