Intracranial self-administration of MDMA into the ventral striatum of the rat: differential roles of the nucleus accumbens shell, core, and olfactory tubercle.
BACKGROUND
Behavioral and anatomical data suggest that the ventral striatum, consisting of the nucleus accumbens and olfactory tubercle, is functionally heterogeneous. Cocaine and D: -amphetamine appear to be more rewarding when administered into the medial olfactory tubercle or medial accumbens shell than into their lateral counterparts, including the accumbens core.


OBJECTIVE
We sought to determine whether rats self-administer the popular recreational drug (+/-)-3,4-methylenedioxymethamphetamine (MDMA) into ventrostriatal subregions and whether the medial olfactory tubercle and medial accumbens shell mediate MDMA's positive reinforcing effects more effectively than their lateral counterparts.


RESULTS
Rats receiving 30 mM MDMA into the medial olfactory tubercle, medial accumbens shell, or accumbens core, but not the lateral tubercle or lateral shell, showed higher self-administration rates than rats receiving vehicle. The medial shell supported more vigorous self-administration of MDMA at higher concentrations than the core or medial olfactory tubercle. In addition, intra-medial shell MDMA self-administration was disrupted by co-administration of the D1 or D2 receptor antagonists SCH 23390 (1-3 mM) or raclopride (3-10 mM).


CONCLUSIONS
Our data suggest that the ventral striatum is functionally heterogeneous. The medial accumbens shell appears to be more important than other ventrostriatal subregions in mediating the positive reinforcing effects of MDMA via both D1- and D2-type receptors. Together with previous data, our data also suggest that unidentified actions of MDMA interfere with the positive reinforcing effects of dopamine in the medial olfactory tubercle.
Shin
Rick
R
Behavioral Neuroscience Research Branch, National Institute on Drug Abuse, National Institutes of Health, US Department of Health and Human Services, Baltimore, MD 21224, USA.
Qin
Mei
M
Liu
Zhong-Hua
ZH
Ikemoto
Satoshi
S
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004298:Dopamine / Q000502:physiology; D006213:Hallucinogens / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D018817:N-Methyl-3,4-methylenedioxyamphetamine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D017072:Neostriatum / Q000502:physiology*; D009714:Nucleus Accumbens / Q000502:physiology*; D009830:Olfactory Bulb / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000187:drug effects; D017448:Receptors, Dopamine D2 / Q000187:drug effects; D012201:Reward; D012646:Self Administration
D006213:Hallucinogens; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D018817:N-Methyl-3,4-methylenedioxyamphetamine; D004298:Dopamine