Animal models of drug addiction, specifically operant self-administration (Davis and Smith, 1976; de Wit and Stewart, 1981), facilitate a mechanistic dissection of the neurophysiology and molecular plasticity that could support human drug addiction. In such experiments, laboratory rodents and non-human primates are trained to manipulate an operandum, such as a lever or nosepoke, which delivers a reinforcer in a contingent fashion. This method of operant, drug self-administration has been utilized for nearly all drugs abused by humans. Importantly, these models involve voluntary drug intake, in contrast to other commonly-used models where animals experience passive drug exposure.
