The Effects of Acute Exposure to Vapourized Δ9-Tetrahydrocannabinol in the Common
Marmoset (Callithrix jacchus): A Pilot Study

  • Emma L. Robertson, MSc, Ontario Veterinary College, University of Guelph
  • Rhonda Kersten, RVT, Schulich School of Medicine and Dentistry, University of Western Ontario
  • Patrick McCunn, PhD, Schulich School of Medicine and Dentistry, University of Western Ontario
  • Andrew Pruszynski, PhD, Schulich School of Medicine and Dentistry, Robarts Research Institute, University of Western Ontario
  • Jibran Khokhar, PhD, Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario

Cannabis is one of the most widely used psychoactive substances around the world and has significant implications for both individuals and society given its legalization and high prevalence use in Canada. Cannabis use is associated with changes in cognitive dysfunctions including impaired memory, associative learning, and attention. While rodent models are used to study the neurological effects of the psychoactive components of cannabis, Δ9-tetrahydrocannabinol (THC), translation of these results to human clinical work is often difficult.

Non-human primates, such as the common marmoset (Callithrix jacchus), show high phylogenetic similarity to humans which makes them an important animal model for human neurological and psychiatric disorders. While the marmoset brain is lissencephalic, it shares similarities in brain architecture and function to humans.

In this pilot study, we optimized blood sampling techniques in awake marmosets in order to do pharmacokinetic studies of vapourized THC in plasma. Baseline plasma samples, MRI brain scans, and behavioural monitoring were collected pre-exposure to THC in 2 marmosets (Callithrix jacchus, 2-3 years, 340-410g, female). Following sample collection, marmosets were placed in a vapourizing cannabis chamber and exposed to cannabis flower (150mg x 3) for 15min. Plasma samples were collected at multiple time points (30min, 1hr, 2hr, 4hr) post-exposure and analyzed for THC concentrations. Video monitoring was used to observe behavioural changes post exposure (i.e. vocalizations, activity, pain response, ataxia). Once we have confirmation that the marmosets were exposed to detectable amounts of THC in the blood, further behavioural studies using touch-screen tasks and brain imaging can be investigated.