RESUMO
The present study compared two putative pharmacotherapies for alcohol abuse and dependence, dehydroepiandrosterone (DHEA) and pregnanolone, with two Food and Drug Administration (FDA)-approved pharmacotherapies, naltrexone and acamprosate. Experiment 1 assessed the effects of different doses of DHEA, pregnanolone, naltrexone, and acamprosate on both ethanol- and food-maintained responding under a multiple fixed-ratio (FR)-10 FR-20 schedule, respectively. Experiment 2 assessed the effects of different mean intervals of food presentation on responding for ethanol under a FR-10 variable-interval (VI) schedule, whereas Experiment 3 assessed the effects of a single dose of each drug under a FR-10 VI-80 schedule. In Experiment 1, all four drugs dose-dependently decreased response rate for both food and ethanol, although differences in the rate-decreasing effects were apparent among the drugs. DHEA and pregnanolone decreased ethanol-maintained responding more potently than food-maintained responding, whereas the reverse was true for naltrexone. Acamprosate decreased responding for both reinforcers with equal potency. In Experiment 2, different mean intervals of food presentation significantly affected the number of food reinforcers obtained per session; however, changes in the number of food reinforcements did not significantly affect responding for ethanol. Under the FR-10 VI-80 schedule in Experiment 3, only naltrexone significantly decreased both the dose of alcohol presented and blood ethanol concentration (BEC). Acamprosate and pregnanolone had no significant effects on any of the dependent measures, whereas DHEA significantly decreased BEC, but did not significantly decrease response rate or the dose presented. In summary, DHEA and pregnanolone decreased ethanol-maintained responding more potently than food-maintained responding under a multiple FR-10 FR-20 schedule, and were more selective for decreasing ethanol self-administration than either naltrexone or acamprosate under that schedule. Experiment 2 showed that ethanol intake was relatively independent of the interval of reinforcement in the food-maintained component, and Experiment 3 showed that naltrexone was the most effective drug at the doses tested when the interval for food reinforcement was low and maintained under a variable-interval schedule.
