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Reinforcement schedule effects in rats trained to discriminate 3,4-methylenedioxymethamphetamine (MDMA) or cocaine.

Daniel Kueh, Lisa E Baker

Psychopharmacology January 2007 DOI: 10.1007/s00213-006-0523-z (opens in new tab)

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AI-extracted from the abstract
Characteristics Observational cohort Peer reviewed
Sample size 32
Population Male Sprague-Dawley rats
Interventions Cocaine MDMA d-amphetamine lysergic acid diethylamide
Dose Cocaine 10 mg/kg, MDMA 1.5 mg/kg
Topics MDMA
Key findings The FR 20 schedule facilitated more rapid discrimination acquisition compared to the VI 15-s schedule, but reinforcement schedule had little influence on stimulus generalization. Cocaine produced partial substitution for MDMA (51% FR 20, 58% VI 15-s), and MDMA produced partial substitution for cocaine (40% FR 20, 72% VI 15-s).

Abstract

Relatively few studies have compared the discriminative stimulus effects of 3,4-methylenedioxymethamphetamine (MDMA) and cocaine, and findings from different laboratories are somewhat inconsistent. One possible reason for discrepant results may be the use of different reinforcement schedules during discrimination training. The present study compared fixed ratio (FR) 20 and variable interval (VI) 15-s reinforcement schedules to determine their influence on discrimination acquisition, response rates, frequency of reinforcements, and stimulus generalization in rats trained to discriminate cocaine or MDMA. Thirty-two male Sprague-Dawley rats were trained to discriminate cocaine (10 mg/kg; n=16) or MDMA (1.5 mg/kg; n=16) from saline under either a FR 20 or a VI 15-s schedule of food reinforcement. Stimulus generalization tests were conducted with a range of doses of cocaine, MDMA, d-amphetamine, and lysergic acid diethylamide in all four training groups. The FR 20 schedule facilitated more rapid discrimination acquisition compared to the VI 15-s schedule and established differential response rates and frequency of reinforcement under drug and vehicle conditions. However, reinforcement schedule had little influence on stimulus generalization between MDMA and cocaine. Cocaine produced partial substitution for MDMA in both training groups (FR 20, 51%; VI 15-s, 58%). Likewise, MDMA produced only partial substitution for cocaine in both training groups (FR 20, 40%; VI 15-s, 72%). The present findings suggest that the number of sessions required to establish discriminative stimulus control varies with different reinforcement schedules. Nevertheless, training schedules alone do not appear to have significant effects on stimulus generalization between MDMA and cocaine.

Comparable studies

Other preclinical and animal studies on MDMA, most cited first.

Study Year Design Participants
Neurotoxicity of the psychedelic amphetamine, methylenedioxymethamphetamine. Rats (implied by typical neurochemical study context) 1987 Experimental study
3,4-Methylenedioxymethamphetamine and 3,4-methylenedioxyamphetamine destroy serotonin terminals in rat brain: quantification of neurodegeneration by measurement of [3H]paroxetine-labeled serotonin uptake sites. Rat brain 1987 Animal experiment
Comparison of the monoamine transporters from human and mouse in their sensitivities to psychostimulant drugs Human and mouse dopamine, norepinephrine, and serotonin transporters expressed in cells 2006 In vitro laboratory study
Small Changes in Ambient Temperature Cause Large Changes in 3,4-Methylenedioxymethamphetamine (MDMA)-Induced Serotonin Neurotoxicity and Core Body Temperature in the Rat Rats 1998 Experimental study
Altered Serotonin Innervation Patterns in the Forebrain of Monkeys Treated with (±)3,4-Methylenedioxymethamphetamine Seven Years Previously: Factors Influencing Abnormal Recovery Squirrel monkeys treated with MDMA 1999 Observational cohort

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