Animal Models of Addiction
Animal Models of the Withdrawal/Negative Affect Stage of the Addiction Cycle
Drug withdrawal from chronic drug administration is usually characterized by responses and effects that are opposite to the acute initial actions of the drug. The physical signs of withdrawal are often drug-specific. Many of the overt physical signs associated with withdrawal from drugs (for example, alcohol and opiates) can be easily observed and quantified, providing specific markers for the study of the neurobiological mechanisms of dependence. Standard rating scales have been developed for opiate, nicotine, and alcohol withdrawal (Gellert and Holtzman, 1978; Malin et al., 1992; Macey et al., 1996).
However, the motivational measures of withdrawal have more validity in understanding the counteradaptive neurobiological mechanisms that drive addiction. Such motivational measures have proved to be extremely sensitive to drug withdrawal and are powerful tools for exploring the neurobiological bases of the motivational aspects of drug dependence.
Animal models of the motivational effects of drug withdrawal include operant schedules, conditioned place aversion, ICSS, the elevated plus maze, and drug discrimination, which include some of the same motivational measures of drug seeking used to characterize the binge/intoxication stage (Table 3.3). Each of these models can address different theoretical constructs associated with a given motivational aspect of withdrawal. Some might reflect general malaise, and others might reflect specific components of the withdrawal syndrome.