Can recreational doses of THC produce significant dopamine release in the human striatum?
BACKGROUND
Cannabis use in early adolescence may be a risk factor for development of schizophrenia. In animals, Delta9-tetrahydrocannabinol (THC) increases the rate of dopamine neuronal firing and release in the striatum. Thus cannabis use may increase dopamine release in the human striatum leading to vulnerability to psychosis.


OBJECTIVE
To investigate whether THC, the main psychoactive component of cannabis, can produce dopamine release in the human striatum.


METHODS
Thirteen healthy volunteers, with previous cannabis experience, underwent two [11C]-raclopride positron emission tomography (PET) scans to indirectly measure striatal dopamine levels following either 10 mg THC or placebo.


RESULTS
Although THC markedly increased psychosis-like symptoms on the Psychotomimetic States Inventory (PSI), there was no significant effect of THC on [11C]-raclopride binding.


CONCLUSIONS
In the largest study of its kind so far, we have shown that recreational cannabis users do not release significant amounts of dopamine from an oral THC dose equivalent to a standard cannabis cigarette. This result challenges current models of striatal dopamine release as the mechanism mediating cannabis as risk factor for schizophrenia.
Stokes
Paul R A
PR
Psychiatry Group, MRC Clinical Sciences Centre, Imperial College, Hammersmith Hospital Campus, London, UK. paul.stokes@imperial.ac.uk
Mehta
Mitul A
MA
Curran
H Valerie
HV
Breen
Gerome
G
Grasby
Paul M
PM
D000328:Adult; D000704:Analysis of Variance; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D013759:Dronabinol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D049268:Positron-Emission Tomography; D011569:Psychiatric Status Rating Scales; D011619:Psychotropic Drugs / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D020891:Raclopride
D011619:Psychotropic Drugs; D020891:Raclopride; D013759:Dronabinol; D004298:Dopamine