System-specific activity in response to Δ9 -tetrahydrocannabinol: a functional magnetic resonance imaging study in awake male rats.

The aim of this study was to assess the effects of two doses of Δ9 -tetrahydrocannabinol (THC, cannabis' main psychoactive agent) and vehicle on blood-oxygen-level dependent (BOLD) activity in drug-naïve, awake rats, in an effort to obtain a THC-specific map of activation in clinically-relevant regions and systems. Intraperitoneal injections of low dose of THC resulted in increased positive and negative BOLD signals compared to vehicle and high dose in areas rich in cannabinoid receptor 1, as well as throughout the pain and hippocampal neural systems. These results offer unique maps of activity, or 'fingerprints', associated with systemic THC administration, allowing for further comparisons with either additional doses or compounds, or between THC administration modalities (i.e. systemic vs. ingested vs. inhaled), which ultimately adds to the translatability assessment of THC-induced BOLD between animal and human studies.