Acquisition of behavioral tolerance to ethanol as a function of reinforced practice in rats.

The roles of both reward and the amount of reinforced practice on the development of behavioral tolerance to ethanol were studied in 32 hooded rats in a Skinner-box situation. The effects of ethanol were evaluated on two aspects of the bar-press response (FR15): latency to complete 15 bar presses and proficiency to earn rewards. Results showed that the behavioral tolerance, as indicated by diminishing effects of ethanol on performances over repeated exposures, developed rapidly. The extent of the developed tolerance was greater and more stable in animals which had reinforced practice while under the influence of ethanol than in animals which had non-reinforced practice. Animals which were exposed to the same amount of ethanol but practiced the response in a non-drug state showed little sign of tolerance to ethanol. These findings give further support to a previous view that learning processes may be involved in acquisition of behavioral tolerance to ethanol.