Striatal D(2)/D(3) receptor availability is inversely correlated with cannabis consumption in chronic marijuana users.
BACKGROUND
Although the incidence of cannabis abuse/dependence in Americans is rising, the neurobiology of cannabis addiction is not well understood. Imaging studies have demonstrated deficits in striatal D(2)/D(3) receptor availability in several substance-dependent populations. However, this has not been studied in currently using chronic cannabis users.


OBJECTIVE
The purpose of this study was to compare striatal D(2)/D(3) receptor availability between currently using chronic cannabis users and healthy controls.


METHODS
Eighteen right-handed males age 18-34 were studied. Ten subjects were chronic cannabis users; eight were demographically matched controls. Subjects underwent a [(11)C]raclopride (RAC) PET scan. Striatal RAC binding potential (BP(ND)) was calculated on a voxel-wise basis. Prior to scanning, urine samples were obtained from cannabis users for quantification of urine Δ-9-tetrahydrocannabinol (THC) and THC metabolites (11-nor-Δ-9-THC-9-carboxylic acid; THC-COOH and 11-hydroxy-THC;OH-THC).


RESULTS
There were no differences in D(2)/D(3) receptor availability between cannabis users and controls. Voxel-wise analyses revealed that RAC BP(ND) values were negatively associated with both urine levels of cannabis metabolites and self-report of recent cannabis consumption.


CONCLUSIONS
In this sample, current cannabis use was not associated with deficits in striatal D(2)/D(3) receptor availability. There was an inverse relationship between chronic cannabis use and striatal RAC BP(ND). Additional studies are needed to identify the neurochemical consequences of chronic cannabis use on the dopamine system.
Indiana University Center for Neuroimaging, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Daniel S
DS
Albrecht
Patrick D
PD
Skosnik
Jennifer M
JM
Vollmer
Margaret S
MS
Brumbaugh
Kevin M
KM
Perry
Bruce H
BH
Mock
Qi-Huang
QH
Zheng
Lauren A
LA
Federici
Elizabeth A
EA
Patton
Christine M
CM
Herring
Karmen K
KK
Yoder
D000293:Adolescent; D000328:Adult; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000000981:diagnostic imaging / Q000378:metabolism*; D008385:Marijuana Smoking / Q000378:metabolism*; D011877:Radionuclide Imaging; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D050637:Receptors, Dopamine D3 / Q000378:metabolism*
D017448:Receptors, Dopamine D2; D050637:Receptors, Dopamine D3; D004298:Dopamine