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The rewarding properties of MDMA are preserved in mice lacking µ‐opioid receptors
Author(s) -
Robledo Patricia,
Mendizabal Victoria,
Ortuño Jordi,
De La Torre Rafael,
Kieffer Brigitte L.,
Maldonado Rafael
Publication year - 2004
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2004.03532.x
Subject(s) - nucleus accumbens , dopamine , opioid , conditioned place preference , dopaminergic , chemistry , mdma , pharmacology , dopamine receptor , homovanillic acid , opioid receptor , knockout mouse , receptor , microdialysis , neuroscience , psychology , biology , serotonin , biochemistry
The involvement of µ‐opioid receptors in the rewarding properties of MDMA was explored in µ‐opioid receptor knockout mice using the conditioning place preference paradigm. The associated release of dopamine in the nucleus accumbens was investigated by in vivo microdialysis. A significant rewarding effect of MDMA (10 mg/kg, i.p.) was observed in both wild‐type and µ‐opioid receptor knockout mice. MDMA (10 mg/kg, i.p.) also induced similar increases in dopamine and decreases in 3,4‐dihydroxyphenylacetic acid and homovanillic acid in the nucleus accumbens dialysates of both wild‐type and µ‐opioid receptor knockout mice. No significant differences in basal levels of dopamine, 3,4‐dihydroxyphenylacetic or homovanillic acids between wild‐type and µ‐opioid receptor knockout mice were observed. In summary, the present results suggest that, in contrast to what has been reported for other drugs of abuse such as opioids, ethanol, nicotine and Δ 9 ‐tetrahydrocannabinol, µ‐opioid receptors do not play a major role in the rewarding properties of MDMA. These differences could be due to distinct mechanisms controlling dopamine release in the nucleus accumbens and suggest that the effects of MDMA on dopaminergic neurons are independent of µ‐opioid receptors.