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Self-injection of d,1-3,4-methylenedioxymethamphetamine (MDMA) in the baboon
Abstract:
MDMA (d,1-3,4-Methylenedioxymethamphetamine HCl; "ecstasy") self-injection (0.1-3.2 mg/kg/injection) was examined in baboons under conditions in which baseline responding was maintained by intravenous injections of cocaine HCl (0.32 mg/kg/injection). Drug was available under a FR 160-response schedule of intravenous injection. Each drug injection was followed by a 3-h time out allowing a maximum of eight injections per day. MDMA or MDMA vehicle (saline) was substituted for cocaine for a period of 14 or more days followed by a return to the cocaine baseline. MDMA (0.32-3.2 mg/kg/inj) maintained more injections and higher responses rates than were maintained by saline. The maximal number of injections maintained by MDMA and the maximal response rate maintained by MDMA were less than those maintained under baseline conditions with cocaine. The highest dose of MDMA tested maintained a cyclic pattern of self-injection, i.e., days of high numbers of injections intermixed with days of low numbers of injections. At the highest dose of MDMA tested, concurrent food maintained behavior was suppressed to an extent that food intake was also decreased.
Insights
3,4-Methylenedioxymethamphetamine (MDMA) self-injection in baboons showed it maintained responding but less than cocaine. High doses of MDMA caused cyclic injection patterns and suppressed food intake.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy, is a psychoactive drug with stimulant properties.
- Understanding MDMA's reinforcing effects and behavioral impact is crucial for addiction research.
Purpose of the Study:
- To investigate the self-injection patterns and reinforcing efficacy of MDMA in baboons.
- To compare MDMA's effects to a known reinforcing agent, cocaine.
Main Methods:
- Baboons self-injected MDMA (0.1-3.2 mg/kg/injection) or saline under a fixed-ratio (FR 160) schedule.
- Baseline responding was maintained by cocaine (0.32 mg/kg/injection).
- Each injection was followed by a 3-hour timeout, limiting injections to eight per day.
Main Results:
- MDMA maintained higher rates of self-injection and responding compared to saline.
- MDMA's maximal reinforcing effects were lower than those of cocaine.
- The highest MDMA dose induced cyclic self-injection patterns and suppressed food intake.
Conclusions:
- MDMA possesses reinforcing properties in baboons, though less potent than cocaine.
- High-dose MDMA self-administration can lead to irregular intake patterns and significant behavioral disruption, including suppressed feeding.