Ethanol, pentobarbital, and chlordiazepoxide effects in squirrel monkeys responding under fixed-ratio food presentation and stimulus-shock termination schedules.

Ethanol, pentobarbital, and chlordiazepoxide were administered to squirrel monkeys responding under a multiple schedule comprised of two fixed-ratio 100-response schedules (FR 100). Under one FR schedule, the one-hundredth response produced food. Under the other schedule, the one-hundredth response terminated the prevailing stimuli and accompanying schedule of electric shock presentation (stimulus-shock termination). Comparable high response rates were maintained under the two schedules. Each drug produced dose-related decreases in response rates. With all three drugs the effects on all aspects of performance were quantitatively similar for both stimulus-shock termination and food-maintained responding.