Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Psychology

Program Name/Specialization

Behavioural Neuroscience

Faculty/School

Faculty of Science

First Advisor

Dr. Paul Mallet

Advisor Role

Thesis Supervisor

Abstract

Although people have smoked cannabis for millennia, administration of cannabis by heating the dried plant material or distilled extracts to a temperature just below the combustion point (i.e., vapourization or "vaping") has rapidly increased over the past few years (Javadi-Payder, Cole, and Taffe, 2018; Manwell, Charchoglyan, Brewer, Matthews, Heipel, and Mallet, 2014). Conversely, most of the cannabinoid research using rodent models has used parenteral routes of administration to examine the effects of purified cannabis extracts such as ∆9-tetrahydrocannabinol (THC), making it difficult to directly compare laboratory research to human drug use. Building on previous studies showing that THC injection in rats impairs memory via a CB1 receptor-mediated mechanism (Mallet & Beninger, 1998), the present study used the delayed-match-to-position (DMTP) task to show that acute exposure to a vapourized cannabis extract (three exposure levels and a control vapour condition) dose-dependently impaired memory in rats. Cannabis vapour-induced memory impairments were attenuated--albeit not significantly--by the CB1 receptor inverse agonist / antagonist rimonabant (3 mg/kg, i.p.). In a separate experiment, brains of rats were harvested 2 hours after exposure to cannabis or control vapour, then drug-induced changes in neural activity were quantified using Fos immunochemistry (IR). Results revealed that cannabis vapour significantly increased neuronal activity in the paraventricular nucleus of the hypothalamus (PVN), paraventricular thalamic nucleus, and the primary somatosensory cortex (S1). This study demonstrates for the first time that exposure to vapourized cannabis impairs memory in rodents, and also serves to provide a novel methodological approach to studying the effects of inhaled cannabis in rodents that better approximates modern human cannabis use. Further studies using this novel drug delivery system can be used to better inform public health guidelines and policy makers about the behavioural and physiological effects of vapourized cannabis.

Convocation Year

2023

Convocation Season

Spring

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