Summary of Animal Models of Addiction
Most of the animal models discussed in this section have predictive validity for certain components of the addiction cycle and generate reliable effects in animals. For the positive reinforcing effects of drugs, drug self-administration, ICSS, and conditioned place preference each have predictive validity. Drug discrimination has predictive validity indirectly through generalization to the training drug. Animal models of withdrawal focus on the motivational components of withdrawal rather than overt somatic signs. Animal models of conditioned drug effects can predict the potential for conditioned drug effects in humans. Animal models of vulnerability in rats show promise for identifying factors that promote individual differences in the initial sensitivity to the rewarding effects of drugs and individual differences in developing compulsive-like responding for drugs with extended access. Achieving predictive validity is more problematic for constructs such as craving because of the nebulous conceptualizations and various definitions of craving in humans. Virtually all of the measures described herein for animal models of addiction have demonstrated reliability, consistency, stability of the measures, small within-subject and between-subject variability, and reproducibility of the phenomena.
Much remains to be explored about the face validity and predictive validity of unconditioned positive and negative motivational states, particularly the conditioned positive and negative motivational states associated with drug use and withdrawal. However, the gaps in our knowledge may lie more in the human clinical laboratory domain than in the animal models themselves (Koob, 2009). Determining the specific changes in the central nervous system associated with these models will provide further insights into both drug dependence and psychopathologies associated with anxiety and affective disorders. Animal models of addiction provide the foundation to begin such studies.