Drugs with powerful reinforcing properties (amphetamine, cocaine, and morphine) require fewer and shorter conditioning trials then a weaker reinforcing drug (nicotine). Drugs with a very short half-life may allow a researcher to run a drug session in the morning and a vehicle session in the afternoon.
The number of drug and vehicle training sessions should be equal. Number of testing sessions in CPP or CPA is one. The test session is in a non-drugged state.
Comment — A criticism of CPP or CPA is testing in a non-drug state when conditioning in a drugged state creates the potential of confounding by state dependent learning. State dependent learning takes place when an animal is conditioned to the interaction between exteroceptive cues and interoceptive cues, but then tested with only exteroceptive cues. This dilemma potentially arises for weak reinforcing drugs. Adding a test session in the drugged state will determine if state dependent learning was a factor in the conditioning. Additional test sessions for evaluation of agonist and antagonist are helpful in developing a complete behavioral and pharmacological profile of the test drugs.
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