Cannabis induced dopamine release: an in-vivo SPECT study

In a research study aimed at examining the alterations in dopaminergic function in schizophrenia, the authors identified a surreptitious case scenario which provided new insights into the subjective and neurochemical effects of cannabis. A 38-year-old drug-free schizophrenic patient took part in a single photon emission computerized tomographic (SPECT) study of the brain, and smoked cannabis secretively during a pause in the course of an imaging session. Cannabis had an immediate calming effect, followed by a worsening of psychotic symptoms a few hours later. A comparison of the two sets of images, obtained before and immediately after smoking cannabis, indicated a 20% decrease in the striatal dopamine D-2 receptor binding ratio, suggestive of increased synaptic dopaminergic activity. This observation offers a plausible biological explanation for the psychotogenic effects of cannabis in vulnerable individuals, and also raises speculations about an interaction between cannabinoid and dopaminergic systems in the brain reward pathways. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.