ABSTRACT
Drug addiction is a chronically relapsing disorder defined as a compulsion to take a drug with loss of control over drug intake. The term “substance dependence” is used to describe a syndrome basically equivalent to addiction, and the diagnostic criteria used describe symptoms that lead to loss of control in drug intake. The motivating factors for the development, maintenance, and persistence of drug addiction can be broken down into four major sources of reinforcement in drug dependence: positive reinforcement, negative reinforcement, conditioned positive reinforcement, and conditioned negative reinforcement. Historically, neuronal systems have been hypothesized to respond to chronic drug insult by counter-adaptive responses. The neuronal circuits forming the medial forebrain bundle have long been hypothesized to be the neural substrates of reward. Drug dependence not only involves acquisition of drug taking and maintenance of drug taking, but also functions as a chronic relapsing disorder with reinstatement of drug taking after detoxification and abstinence.
