Animal Models of the Binge/Intoxication Stage of the Addiction Cycle
Drug discrimination procedures can identify the relative reinforcing effects of drugs, thus indicating the relative abuse potential of these drugs (Holtzman, 1990). In this procedure, an animal is trained to emit a particular response (like pressing the right lever) for a food reinforcer in a drug-induced state and then to emit a different response (like pressing the left lever) for the same food reinforcer in a placebo-induced or nondrug state. The interoceptive cue state produced by the drug controls the behavior as a discriminative stimulus or cue that informs the animal to make the appropriate response to gain reinforcement. So if a rat is trained to respond on the left lever while intoxicated with D-amphetamine and the right lever when given vehicle injections while not intoxicated, then on the test day the rat will be given methamphetamine and allowed to choose. The rat will choose the D-amphetamine lever. In such a test, the rat “reports” its internal drug-like state caused by methamphetamine. The choice of the response that follows administration of an unknown test compound can provide valuable information about the similarity of that drug’s interoceptive cue properties to those of the training drug.