Tolerance to the Effects of Cocaine on Performance Under Behavior‐correlated Reinforcement Magnitude

Abstract

Four pigeons responded under a fixed-interval 8-min schedule of food delivery in which the amount of food delivered at the end of each interval depended on performance during the interval (i.e., a correlated schedule). Specifically, duration of access to grain was contingent upon the number of responses made during the first 4 min of the interval. This differential outcome did not affect response rates or patterning relative to performance under a simple fixed-interval 8-min schedule. Behavior under the correlated schedule was then investigated under doses of cocaine ranging from 0.3 to 10.0 mg/kg. A bitonic dose-response function was obtained for response rates and the time with head in the food hopper, whereas dose-dependent decreases were observed in the mathematical index of curvature (Fry, Kelleher, & Cook, 1960). The dose that produced the greatest increase in the head-in-hopper time was then administered prior to each session. Following repeated administration of cocaine, disruptions in response patterning were attenuated for all 4 pigeons; tolerance was also observed to the rate-increasing effects and increased head-in-hopper time for 2 pigeons after chronic cocaine administration. Tolerance therefore developed despite the fact that the initial effect of cocaine was to increase the amount of food obtained.Key words: fixed-interval schedule, cocaine, tolerance, reinforcement loss, correlated schedule, key peck, pigeonsTolerance is characterized by a reduction in the potency of a drug in producing an effect after repeated administration, and can be measured in terms of changes in operant performance. Tolerance to the effects of cocaine on operant performance has been observed under several conditions of response-dependent reinforcement (e.g., Branch, Walker, & Brodkorb, 1998;Hoffman, Branch, & Sizemore, 1987;Hughes & Branch, 1991;Poling & Nickel, 1993;Schama & Branch, 1994;Smith, 1990;Stafford & Branch, 1996;van Haaren & Anderson, 1994).An influential view of how behavioral factors can influence the development of tolerance is the reinforcement-loss hypothesis (Schuster & Zimmerman, 1961), which states that tolerance is more likely to develop if deThis research was supported by USPHS Grant DA04074 from the National Institute on Drug Abuse. Data from the study provided the basis for a Masters thesis for the first author, and data from the first two phases served as a Masters thesis for the second author. We thank Brian Iwata and Tim Hackenberg for helpful comments on earlier versions of this manuscript, and Margaret Gratton, Jonathan Pinkston, and Jin Ho Yoon for assistance in experimentation.Reprints can be obtained from either the first or third author at the Department of Psychology, Box 112250, University of Florida, Gainesville, Florida 32611 (E-mail: mmiller1@ufl.edu or branch@ufl.edu).creased reinforcement rate results from the initial drug effect. For example, Schuster, Dockens, and Woods (1966) observed rats' performance on a two-component multiple schedule first under acute (once every few days) a...

Resistance of temporally controlled behavior to change

“…The QL and the IC are both independent of average rate of responding. The IC is sensitive to fluctuations in response patterns (Miller, Brodkorb, & Branch, 2001). At the same time, the IC has been shown to be inappropriate when analyzing intervals with few responses (Baron & Leinenweber, 1995).…”