Place conditioning in a three- or four-choice apparatus: role of stimulus novelty in drug-induced place conditioning.

A series of 4 experiments examined the suggestion (Scoles & Siegel, 1986) that drug-induced place preference conditioning may be due to interference with habituation. In each experiment, rats had the opportunity to select among a drug-paired chamber, a saline-paired chamber, and a novel (or relatively novel) chamber. The drugs included the positively reinforcing drugs amphetamine, apomorphine, morphine, and nicotine and the aversive drug lithium chloride. The rats preferred chambers that were paired with amphetamine, apomorphine, and morphine more than chambers that were novel; however, they also consistently preferred novel chambers to familiar saline-paired chambers. There was no evidence of place conditioning with nicotine. The drug-induced place preference, but not the novelty preference, occurred after a single conditioning trial in a 3-choice apparatus but not a 4-choice apparatus. Lithium chloride established a place aversion after 1-3 conditioning trials. Measures of activity revealed that the rats were least active while in their most preferred chamber and most active while in their least preferred chamber.