Related Experiment Video
Updated: Nov 20, 2025
A Novel Procedure for Evaluating the Reinforcing Properties of Tastants in Laboratory Rats: Operant Intraoral Self-administration
Published on: February 6, 2014
MDPV "high-responder" rats also self-administer more oxycodone than their "low-responder" counterparts under a fixed
Brenda M Gannon1,2, Kenner C Rice3, Kevin S Murnane4,5,6
1Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Atlanta, GA, 30341, USA.
Rationale:
Oxycodone is one of the most commonly prescribed and most frequently abused opioid analgesics, yet little is known regarding individual vulnerabilities to oxycodone abuse. The synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV) has been shown to produce a "high-responder" phenotype characterized by increased drug intake and responding during periods of signaled drug unavailability (e.g., during post-infusion timeouts) in ~ 40% of male Sprague-Dawley rats. This phenotype also transfers to other psychostimulants (e.g., cocaine and methamphetamine), but it is unknown whether this phenotype transfers to other (non-stimulant) drugs of abuse.
Objectives:
The present study aimed to (1) reestablish the "high-responder" phenotype in male Sprague-Dawley rats (n = 11) that acquired self-administration of MDPV (0.032 mg/kg/inf) on a fixed ratio 1 (FR1) schedule of reinforcement and (2) compare full dose-response curves for MDPV and oxycodone self-administration under an FR5 schedule of reinforcement.
Results:
MDPV was ~ 3-fold more potent at maintaining peak levels of behavior and resulted in greater overall drug intake than oxycodone. High levels of timeout responding were noted in a subset of rats that acquired MDPV self-administration ("high-responders", n = 5), and the FR5 dose-response curve for MDPV was shifted upward for these rats relative to their "low-responder" (n = 6) counterparts. "High-responders" also self-administered more infusions of oxycodone under an FR5 schedule of reinforcement than "low-responders"; however, this was not coupled with increased levels of timeout responding.
Conclusions:
The present data suggest that a subset of individuals with a history of using synthetic cathinones may be particularly vulnerable to the abuse of oxycodone.
