Rewarding properties of the stereoisomers of 4-methylaminorex: involvement of the dopamine system.
4-Methylaminorex is a potential psychostimulant drug of abuse that exists as four stereoisomers: cis-4R,5S, cis-4S,5R, trans-4S,5S, and trans-4R,5R. The racemic mixture of the cis-isomers has been encountered in illicit samples, but previous animal studies suggest that also the trans-isomers could have similar stimulant-like properties. We tested whether the stereoisomers possess rewarding properties and compared their potency using the conditioned place preference method in rats. Furthermore, the involvement of the brain dopaminergic system in the 4-methylaminorex reward was tested with the dopamine D1- and D2-receptor antagonists SCH 23390 and raclopride administered systemically, or with the neurotoxin 6-hydroxydopamine injected into the nucleus accumbens. All the four isomers induced place preference, with no apparent differences in their potency. SCH 23990 and raclopride attenuated 4-methylaminorex-induced increase in place preference, and 6-hydroxydopamine also tended to be efficacious. These findings indicate that all the four stereoisomers of 4-methylaminorex possess rewarding properties and thus abuse potential; the trans-isomers are at least as potent as the cis-isomers. Furthermore, the brain dopaminergic system appears to be involved in the 4-methylaminorex-reward.
Drug Research Unit, National Public Health Institute, Mannerheimintie 166, FIN-00300 Helsinki 30, Finland. esa.meririnne@ktl.fi
Esa
E
Meririnne
Miina
M
Kajos
Aino
A
Kankaanpää
Meri
M
Koistinen
Kalervo
K
Kiianmaa
Timo
T
Seppälä
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001552:Benzazepines / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism; D010080:Oxazoles / Q000737:chemistry / Q000494:pharmacology*; D016627:Oxidopamine / Q000494:pharmacology; D020891:Raclopride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000502:physiology; D017448:Receptors, Dopamine D2 / Q000502:physiology; D012201:Reward; D012701:Serotonin / Q000378:metabolism; D013237:Stereoisomerism
D001552:Benzazepines; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D010080:Oxazoles; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D012701:Serotonin; D020891:Raclopride; C000081:4-methylaminorex; D016627:Oxidopamine; D004298:Dopamine; D009638:Norepinephrine