History of cannabis use is not associated with alterations in striatal dopamine D-2/D-3 receptor availability

Cannabis use in adolescence is emerging as a risk factor for the development of psychosis. In animal studies, Delta 9-tetrahydrocannabinol (THC), the psychoactive component of cannabis, modulates striatal dopaminergic neurotransmission. Alterations in human striatal dopaminergic function have also been reported both in psychosis and in stimulant use. We sought to examine whether striatal dopamine D-2/D-3 receptor availability was altered in volunteers with a history of cannabis use using a database of previously acquired [C-11]-raclopride positron emission tomography (PET) scans. Ten [C-11]-raclopride scans from volunteers with a history of cannabis use were compared to ten control scans using a functional striatal subdivision region of interest (ROI) analysis. No significant differences in either overall striatal BPND values or BPND values in any functional striatal subdivision were found between the two groups. There was also no correlation between lifetime frequency of cannabis use and BPND values. Limbic striatal BPND values were ten percent lower in current nicotine cigarette smokers. These findings suggest that, unlike other drugs of abuse, a history of cannabis use is not associated with alterations in striatal dopamine D-2/D-3 receptor availability.