Biology subjects

Onofrychuk, T. J.

Publications and source records attributed to Onofrychuk, T. J..

2 recordsLinked to original sources

bioRxiv2023

High-THC Cannabis smoke impairs working memory capacity in spontaneous tests of novelty preference for objects and odors in rats

Working memory (WM) is an executive function that orchestrates the use of a limited amount of information, referred to as working memory capacity (WMC), in cognitive functions. In humans, Cannabis exposure impairs WM; however, it is unclear if Cannabis facilitates or impairs rodent WM. Existing literature also fails to address the effects of Cannabis exposure on rodent WMC using exposure paradigms that closely mirror patterns of human use. In the present study, WMC of rats was inferred by novelty preference after a short delay in spontaneous recognition-based tests. Either object or odor-based stimuli were used in different variations of the tests that present identical (IOT) and different (DOT) sets of stimuli (3 or 6) for low-and high-cognitive loads, respectively. Additionally, we present a human-machine hybrid (HYB) behavioral quantification approach which supplements stopwatch-based scoring with supervised machine learning (SML)-based classification, enabling behavioral data to be made publicly available. After validating the spontaneous tests, 6-item IOT and DOT tests with the HYB method were used to evaluate the impact of acute exposure to high-THC or high-CBD Cannabis smoke on novelty preference. Under control conditions, rats showed novelty preference in all test variations. We found that high-THC, but not high-CBD, Cannabis smoke exposure impaired novelty preference for objects under a high-cognitive load. Odor-based recognition deficits were seen under both low-, and high-cognitive loads only following high-THC smoke exposure. Ultimately, these data show that Cannabis smoke exposure impacts novelty preference in a load-dependent, and stimuli-specific manner. Significance StatementWorking memory (WM) capacity is the limited amount of information that can be utilized by WM to orchestrate processes like learning and memory. Using object-and odor-based spontaneous recognition tests, the impact of high-THC or high-CBD Cannabis smoke on novelty preference was evaluated. Behavioral measurements were generated using a combination of open-source analysis software and traditional stopwatch scoring to form a human-machine hybrid (HYB) scoring method. We show novelty preference deficits under high-cognitive loads in object-based tests, while impacting novelty preference under both high-and low-cognitive loads in the odor-based tests. Ultimately, we show that Cannabis smoke exposure affects cognitive functions that underly WM in rats, which has broad implications for human use.

neuroscience↗

bioRxiv2023

Repeated exposure to high-THC Cannabis smoke during gestation alters sex ratio, behavior, and amygdala gene expression of Sprague Dawley rat offspring

Due to the recent legalization of Cannabis in many jurisdictions and the consistent trend of increasing THC content in Cannabis products, there is an urgent need to understand the impact of Cannabis use during pregnancy on fetal neurodevelopment and behavior. To this end, we repeatedly exposed female Sprague-Dawley rats to Cannabis smoke from gestational days 6 to 20 (n=12; Aphria Mohawk; 19.51% THC, <0.07% cannabidiol) or room-air as a control (n=10) using a commercially available system. Maternal reproductive parameters, behavior of the adult offspring, and gene expression in the offspring amygdala were assessed. Body temperature was decreased in dams following smoke exposure and more fecal boli were observed in the chambers before and after smoke exposure in those dams exposed to smoke. Maternal weight gain, food intake, gestational length, litter number, and litter weight were not altered by exposure to Cannabis smoke. A significant increase in the male-to-female ratio was noted in the Cannabis-exposed litters. In adulthood, both male and female Cannabis smoke-exposed offspring explored the inner zone of an open field significantly less than control offspring. Gestational Cannabis smoke exposure did not affect behavior on the elevated plus maze test or social interaction test in the offspring. Cannabis offspring were better at visual pairwise discrimination and reversal learning tasks conducted in touchscreen-equipped operant conditioning chambers. Analysis of gene expression in the adult amygdala using RNAseq revealed subtle changes in genes related to development, cellular function, and nervous system disease in a subset of the male offspring. These results demonstrate that repeated exposure to high-THC Cannabis smoke during gestation alters maternal physiological parameters, sex ratio, and anxiety-like behaviors in the adulthood offspring. Significance statementCannabis use by pregnant women has increased alongside increased THC content in recent years. As smoking Cannabis is the most common method of use, we used a validated model of Cannabis smoke exposure to repeatedly expose pregnant rats to combusted high-THC Cannabis smoke. Our results show alterations in litter sex ratio, anxiety-like behavior, and decision making in the offspring which may relate to subtle changes in expression of amygdala genes related to development, cellular function, and nervous system disease. Thus, we believe this gestational Cannabis exposure model may be useful in delineating long-term effects on the offspring.

neuroscience↗