The conditioned place preference paradigm is a standard preclinical behavioral model used to study the rewarding and aversive effects of drugs. Although a number of different designs and apparatuses are used in this model, the basic characteristics of this task involve the association of a particular environment with drug treatment, followed by the association of a different environment with the absence of the drug (i.e., the drug’s vehicle). A common variation of this design consists of a three-compartment chamber with the outer compartments being designed to have different characteristics (e.g., white vs. black walls, pine vs. corn bedding, horizontal grid vs. cross-grid flooring). The center compartment has no special characteristics and is not paired with a drug, and the gates between the compartments can be opened to allow an animal to pass freely between them. During training, an animal (typically a rat or mouse) is given an injection of a drug with potentially rewarding or aversive properties, and is then placed into one of the outer compartments for several minutes. On the following day, the rat is injected with the drug’s vehicle and then placed in the opposite compartment. Generally, these daily sessions alternate between drug and vehicle for 2 or 3 days each. Afterward, a test session is conducted, which consists of placing the animal in the center compartment and then, after opening the gates to both of the outer compartments, recording the time the animal spends in each of the outer compartments during the session. A conditioned place preference (CPP) is found if the animals spend significantly more time in the drug-paired compartment versus the vehicle-paired compartment. On the other hand, if the animals spend significantly more time in the vehicle-paired compartment versus the drug-paired compartment, then this is considered a conditioned place aversion (CPA). Typically, drugs of abuse, such as cocaine, produce CPP, and drugs that elicit aversive effects, such as lithium chloride, produce CPA. As with other behavioral models used in pharmacology research, the behavioral effects of drugs used in the CPP paradigm depend on species, strain, route of administration, time interval of drug administration, dose concentration, and the CPP apparatus used. Many drugs of abuse produce both CPP and CPA, depending on the dose administered. In drug-dependent animals, withdrawal effects generally produce CPA. Because the CPP paradigm generally provides a reliable indicator for studying the rewarding effects of drugs that require relatively little training compared to self-administration paradigm, the CPP paradigm has been commonly used in conjunction with standard neuroscience techniques to elucidate the subjective effects of drugs (Table 4.1).
Record the level of illumination in the room. Illuminance = Light Falling on a Surface. The amount of light falling on a surface is "illuminance", and is measured in lux (metric unit = lumen/m2) or foot-candles (English unit = lumen/ft2). 1 foot-candle equals 10.8 lux.