Methodological and analytical issues of progressive ratio schedules: Definition and scaling of breakpoint.

Autor: Tsibulsky VL; Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA. Electronic address: vladimir.tsibulsky@uc.edu., Norman AB; Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, 45267, USA.
Jazyk: angličtina
Zdroj: Journal of neuroscience methods [J Neurosci Methods] 2021 May 15; Vol. 356, pp. 109146. Date of Electronic Publication: 2021 Mar 23.
DOI: 10.1016/j.jneumeth.2021.109146
Abstrakt: Background: The break point (BP) of the progressive ratio (PR) schedule of drug delivery is a well-recognized parameter in self-administration studies. Nonetheless, two problems remain unresolved: there is no rationally justified criterion for the last response at BP; the both commonly used definitions of BP as the number of deliveries or the last complete progressive ratio requirement are not the best assuming that BP is a measure of motivation.
New Method: A criterion for the last lever press is proposed in this study using intravenous cocaine self-administration in rats. The rationale is based on the finding that long inter-press intervals have initially very low probability to occur during the self-administration phase of the session under the PR schedule. But this probability dramatically increases when inter-injection intervals increase due to high ratio requirements.
Results: For cocaine these critical inter-press intervals were 7.5 min and longer. This novel criterion was applied to measure BP according to all four theoretically plausible definitions of BP including the new one: the higher of the two numbers of presses before or after the last delivery of the reinforcer.
Comparison With Existing Method: The conventionally defined BP is significantly lower (by 12 %) than BP defined according to the new proposed definition. The new definition of BP provides not only a more accurate value of BP but now the variance of BP at different cocaine doses is homogeneous as required by many statistical tests.
Conclusion: These new definitions of the last press and BP provide more accurate and statistically homogenous measure of BP.
(Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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