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Effect of once weekly treatment with 3,4-methylenedioxymethamphetamine on schedule-controlled behavior in rats
R Nagilla1, M C Newland, J Snyder
1Department of Pharmacal Sciences, Auburn University, AL 36849, USA.
Abstract:
The present study examined the effects of 3,4-methylenedioxymethamphetamine (MDMA), before and after once a week dosing, on the behavior of rats responding under a fixed ratio 20 schedule of reinforcement. Acutely, cumulative doses of MDMA dose-dependently decreased responding when compared to a series of water injections. Rats were then separated into two groups, one of which received only weekly MDMA ('paired') while the other received an additional injection of water each week ('unpaired'). Weekly dosing with MDMA resulted in significantly increased responding at low doses in the paired group but not in the unpaired group. When water injections were readministered there was a significant increase in responding in both groups. During the weekly regimen, locomotor activity also increased significantly over time after both water and MDMA injections. In conclusion, it appears that even weekly dosing with a small amount of MDMA can have long-lasting effects that are manifested in both operant and spontaneous behavior and that may be mediated by a conditioning mechanism.
Insights
Weekly 3,4-methylenedioxymethamphetamine (MDMA) dosing in rats led to lasting behavioral changes, suggesting a conditioning mechanism influences operant and spontaneous activity.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
- Psychopharmacology
Background:
- 3,4-methylenedioxymethamphetamine (MDMA) is a psychoactive drug with known effects on behavior.
- Understanding the long-term consequences of repeated MDMA exposure is crucial for assessing its potential impact.
Purpose of the Study:
- To investigate the behavioral effects of acute and repeated weekly dosing of MDMA in a rat model.
- To explore whether conditioning mechanisms play a role in the long-term behavioral changes induced by MDMA.
Main Methods:
- Rats were trained to respond under a fixed ratio 20 schedule of reinforcement.
- Acute MDMA doses were administered to assess immediate effects on responding.
- Rats received weekly injections of MDMA (paired group) or water (unpaired group) for a defined period.
- Locomotor activity was monitored throughout the study.
Main Results:
- Acute MDMA administration dose-dependently decreased responding.
- Weekly MDMA dosing in the paired group, but not the unpaired group, significantly increased responding at low doses.
- Locomotor activity increased significantly over time in both groups after injections.
- Re-administration of water injections led to increased responding in both groups.
Conclusions:
- Even infrequent, low-dose MDMA exposure can induce persistent changes in operant and spontaneous behavior.
- Conditioning mechanisms may mediate the long-lasting behavioral effects of MDMA.
- Repeated MDMA administration can alter behavioral responses beyond its acute pharmacological effects.