Assessment of the discriminative stimulus effects of the optical isomers of ecstasy (3,4-methylenedioxymethamphetamine; MDMA).
The discriminative stimulus effects of the stereoisomers of 3,4-methylenedioxymethamphetamine (MDMA) were studied in rats trained to discriminate 1.25mg/kg of (+)-MDMA or 3.5mg/kg of (-)-MDMA from saline, in a two lever, water-reinforced, drug discrimination situation. The isomers of MDMA and 3,4-methylenedioxyamphetamine (MDA) substituted completely for both training drugs. The stimulants amphetamine and cocaine did not substitute for either MDMA isomer. The hallucinogens (+/-)-2,5-dimethoxy-4-methylamphetamine (DOM), (+)-lysergic acid diethylamide (LSD), and mescaline failed to substitute completely for (+)-MDMA. Similarly, DOM and mescaline did not substitute for (-)-MDMA; however, LSD did substitute for this isomer at a dose of 0.06mg/kg but not at higher doses. Substitution tests with 5-HT-releasing agents revealed that fenfluramine substituted partially for (+)-MDMA and completely for (-)-MDMA, while p-chloroamphetamine substituted completely for both isomers of MDMA. When given in combination with (+)-or (-)-MDMA, neither the 5-HT(2) antagonist pirenpirone nor the less selective 5-HT antagonist metergoline consistently blocked drug-appropriate responding. These results indicate that the stereoisomers of MDMA and MDA have similar discriminative stimulus properties. More importantly, the present findings suggest that 5-HT release may be important for the discriminative stimulus effects of (+)-and (-)-MDMA. Actions at 5-HT(2) receptors, however, do not appear to be critical.
Department of Psychology, University of South Carolina, Columbia, S.C.
L.E.
LE
Baker
J.
J
Broadbent
E.K.
EK
Michael
P.K.
PK
Matthews
C.A.
CA
Metosh
R.B.
RB
Saunders
W.B.
WB
West
J.B.
JB
Appel