title: Conjunctive schedules of reinforcement. I. Rate-dependent effects of pentobarbital and d-amphetamine.
abstract: Key pecking of pigeons was maintained under conjunctive schedules of food presentation in which both a fixed-interval and a fixed-ratio schedule had to be completed before a peck produced food. For two pigeons, pecks on a single key completed both schedule requirements (fixed-interval 3-min, fixed-ratio 50 for one bird, fixed-interval 5-min, fixed-ratio 50 for the second). For two other pigeons, each requirement was scheduled on a separate key. On the two-key schedule, a peck after 5 min on the key scheduling the fixed-interval requirement produced food if at least 10 pecks had occurred on the ratio key (conjunctive fixed-interval 5-min, fixed-ratio 10). When each requirement was scheduled on a separate key, response rates on the fixed-ratio key were generally higher in the early portion of the interval and declined as the interval progressed; responding on the fixed-interval key, once initiated, typically remained at a constant rate throughout the interval. Responding under the single-key schedule was characterized by a high rate early in the interval; this then changed to a lower rate that continued until a peck produced food. For all pigeons, increases in response rates with pentobarbital and d-amphetamine were inversely related to the control rate of responding. When equivalent rates on each key of the two-key schedule were compared, both drugs increased rates on the fixed-ratio key less. Although the effects of both drugs were rate dependent, each drug differentially modified the pattern of responding under the single-key schedule.
mesh_terms: D000818:Animals; D010856:Columbidae; D003216:Conditioning, Operant / Q000187:drug effects*; D003864:Depression, Chemical; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007273:Injections, Intramuscular; D008297:Male; D010424:Pentobarbital / Q000008:administration & dosage / Q000494:pharmacology*; D011930:Reaction Time; D012055:Reinforcement Schedule; D013268:Stimulation, Chemical
chemical_list: D010424:Pentobarbital; D003913:Dextroamphetamine