title: Reinforcement magnitude modulation of rate dependent effects in pigeons and rats.
abstract: Response rate can influence the behavioral effects of many drugs. Reinforcement magnitude may also influence drug effects. Further, reinforcement magnitude can influence rate-dependent effects. For example, in an earlier report, we showed that rate-dependent effects of two antidepressants depended on reinforcement magnitude. The ability of reinforcement magnitude to interact with rate-dependency has not been well characterized. It is not known whether our previous results are specific to antidepressants or generalize to other drug classes. Here, we further examine rate-magnitude interactions by studying effects of two stimulants (d-amphetamine [0.32-5.6 mg/kg] and cocaine [0.32-10 mg/kg]) and two sedatives (chlordiazepoxide [1.78-32 mg/kg] and pentobarbital [1.0-17.8 mg/kg]) in pigeons responding under a 3-component multiple fixed-interval (FI) 300-s schedule maintained by 2-, 4-, or 8-s of food access. We also examine the effects of d-amphetamine [0.32-3.2 mg/kg] and pentobarbital [1.8-10 mg/kg] in rats responding under a similar multiple FI300-s schedule maintained by 2- or 10- food pellet (45 mg) delivery. In pigeons, cocaine and, to a lesser extent, chlordiazepoxide exerted rate-dependent effects that were diminished by increasing durations of food access. The relationship was less apparent for pentobarbital, and not present for d-amphetamine. In rats, rate-dependent effects of pentobarbital and d-amphetamine were not modulated by reinforcement magnitude. In conclusion, some drugs appear to exert rate-dependent effect which are diminished when reinforcement magnitude is relatively high. Subsequent analysis of the rate-dependency data suggest the effects of reinforcement magnitude may be due to a diminution of drug-induced increases in low-rate behavior that occurs early in the fixed-interval.
authors.affiliation: Department of Psychiatry, Auburn University,226 Thach Hall, Auburn, AL 36849, USA. correcj@auburn.edu
authors.forename: Brett C
authors.initials: BC
authors.lastname: Ginsburg
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Pinkston
authors.forename: R J
authors.initials: RJ
authors.lastname: Lamb
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D002707:Chlordiazepoxide / Q000008:administration & dosage / Q000494:pharmacology; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology; D010856:Columbidae; D003216:Conditioning, Operant / Q000187:drug effects; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005502:Food; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D010424:Pentobarbital / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D012055:Reinforcement Schedule; D013997:Time Factors
chemical_list: D000697:Central Nervous System Stimulants; D006993:Hypnotics and Sedatives; D002707:Chlordiazepoxide; D010424:Pentobarbital; D003042:Cocaine; D003913:Dextroamphetamine