European Journal of Neuroscience
November 16, 2007
Susan Schenk, Lincoln S. Hely, Barbara Lake et al.
113 citations
MDMA self-administration was studied in previously drug-naïve rats. Acquisition varied widely, with about 60% of rats learning to self-administer MDMA over 15 days, a lower rate and slower onset than for cocaine. Responding depended on dose, and breakpoints under a progressive ratio schedule increased with dose. Rats that self-administered MDMA showed lower densities of serotonin transporter sites (SERT) across brain regions, comparable to reductions from experimenter-administered MDMA. The findings indicate MDMA has high abuse liability and that long-term self-administration may cause lasting deficits in serotonin neurotransmission.
British Journal of Pharmacology
December 30, 2010
Susan Schenk, David Gittings, Joyce Colussi‐mas
61 citations
In rats trained to self-administer MDMA (ecstasy), a light cue previously paired with the drug triggered drug-seeking behavior. This effect was amplified by priming injections of drugs that activate dopamine D2-like receptors (quinpirole, amphetamine, GBR 12909) but not by a D1-like receptor agonist (SKF 81297), the non-selective dopamine agonist apomorphine, or serotonin (5-HT) receptor agonists. A serotonin uptake inhibitor reduced cue-induced drug-seeking but did not block the potentiation caused by a dopamine uptake inhibitor. Blocking either D1 or D2 receptors attenuated the MDMA-enhanced drug-seeking. The findings suggest that after repeated MDMA use, dopamine pathways become more influential in driving relapse to drug-seeking, partly because MDMA reduces brain serotonin levels.
Behavioral Neuroscience
January 1, 2006
Evangeline Daniela, David Gittings, Susan Schenk
37 citations
Rats pressed a lever to receive intravenous MDMA, and their responding increased when the required number of presses rose from 1 to 5, decreased when saline replaced MDMA, and increased again when MDMA was restored. During training, each MDMA infusion was accompanied by a light. After an average of 19 daily sessions, omitting either the light or the drug caused responding to decline gradually over 15 days. Omitting both the light and the drug produced a dramatic and lasting decrease in responding. These results suggest that cues paired with MDMA acquire conditioned properties that may contribute to drug-taking behavior.