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Influence of “unit price”
on schedule-parameter dependent tolerance to cocaine. Tolerance to cocaine’s rate-decreasing effects on operant behavior has been shown to be dependent on ratio schedule parameter. This effect is robust and has been reported in several studies from several laboratories. The usual nature of the effect is that performance under large ratio schedules is less likely to display tolerance following repeated administration of the drug than is performance under smaller ratios. When different ratios have been used, reinforcer magnitude has been held constant. That results in different “unit prices” (reinforcement amount per response) under the different schedules. In our experiment we established performance under three fixed-ratio parameters, FR10, FR30, and FR100. Time of access to food at the end of each ratio was adjusted so that equal unit prices occurred under each FR. Equating unit price diminished substantially the differences in effects of cocaine, given both acutely and chronically, across ratio parameter. Keywords: cocaine, tolerance, unit price |
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