Animal Models of the Binge/Intoxication Stage of the Addiction Cycle
Conditioned Place Preference
Conditioned place preference, or place conditioning, is a non-operant procedure that can also assess the reinforcing effects of drugs using classical or Pavlovian conditioning. In a simple version of the place preference paradigm, animals experience two distinct neutral environments that are paired with distinct drug or nondrug states (Figure 3.7). The animal is then given the choice to enter and explore either environment, and the time spent in the drug-paired environment is considered an index of the reinforcing value of the drug. Animals exhibit a conditioned preference for an environment associated with drugs that function as positive reinforcers (that is, they spend more time in a drug-paired environment than in a placebo-paired environment). They also avoid environments that are paired with aversive states, like drug withdrawal – a paradigm called conditioned place aversion (but more on that in the withdrawal/negative affect section below).
FIGURE 3.4 (A) Lever pressing in rats during the first 15 min after a cocaine injection as a function of the frequency of electrical stimulation of the lateral hypothalamus and cocaine dosage. (B) Self-stimulation frequency threshold (expressed as a percentage of baseline) as a function of cocaine dosage. The data are expressed as the means from the first threshold determination in the first hour after the injection. Each reference (baseline) value is the mean from the two threshold determinations taken just before the respective drug test. [Taken with permission from Bauco P, Wise RA. Synergistic effects of cocaine with lateral hypothalamic brain stimulation reward: lack of tolerance or sensitization. Journal of Pharmacology and Experimental Therapeutics, 1997, (283), 1160–1167.]