title: Changes in sensitivity of response distributions to changing reinforcement ratios during exposure to ephedrine, caffeine, and ephedrine-caffeine combinations.
abstract: Changes in the sensitivity of response distributions to changes in reward distribution (reinforcer distribution sensitivity) were examined when rats were exposed to low and moderate doses of caffeine, ephedrine, and caffeine-ephedrine combinations. The data show significant decreases in sensitivity in response distributions to changes in reward schedule values during exposure to caffeine and ephedrine/caffeine combinations, whereas ephedrine alone resulted in overmatching comparable with baseline and NaCl conditions. Rats treated either with 3.0-mg/kg or 10.0-mg/kg doses of caffeine and all combinations of ephedrine at doses of 1.8 or 5.6 mg/kg with caffeine at 3.0 or 10.0 mg/kg showed reduced sensitivity in response distributions to differences in reinforcement schedule ratios. In contrast, when rats were exposed to ephedrine at 1.8 or 5.6 mg/kg, they maintained or increased the degree of overmatching. Although reinforcer distribution sensitivity was altered, drug exposure did not significantly affect the absolute rates of responding. Bias varied after exposure to caffeine, ephedrine, and their combinations, but not systematically. Finally, whereas the estimates of goodness of fit (r2) to the matching equation showed some decreases during drug exposure, these were neither statistically significant nor correlated with drug dose. These results suggest differential effects of ephedrine and caffeine on the sensitivity of response distributions to changes in reinforcement ratio distributions, with deleterious effects of caffeine and ephedrine/caffeine combinations.
authors.affiliation: Department of Psychology, Illinois State University, Illinois 61790-4620, USA.
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Borre
authors.forename: Seshanand
authors.initials: S
authors.lastname: Chandrashekar
authors.forename: James D
authors.initials: JD
authors.lastname: Dougan
authors.forename: Byron A
authors.initials: BA
authors.lastname: Heidenreich
authors.forename: Valeri
authors.initials: V
authors.lastname: Farmer-Dougan
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004809:Ephedrine / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D012201:Reward; D012646:Self Administration; D012680:Sensitivity and Specificity
chemical_list: D000697:Central Nervous System Stimulants; D004338:Drug Combinations; D002110:Caffeine; D004809:Ephedrine