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Effects of Cannabis Smoke Exposure on Working Memory Performance in Aged Rats

Sabrina Zequeira
University of Florida

Cannabis is the most widely used illicit drug in the United States, with individuals over the age of 65 becoming the fastest growing demographic of cannabis users. Cannabis can have multiples benefits such as serving as a pain management tool, appetite stimulant and sleep aid that make it appealing for individuals coping with age related health conditions.

As the number of older adults in the US expected to reach 90 million by 2050, however, it is imperative to understand the potential cognitive impacts of cannabis use in this population. Across species, aged individuals exhibit deficits in cognitive functions supported by the prefrontal cortex(PFC) and the hippocampus.

These same cognitive functions are impaired by acute administration of cannabis or delta-9-tetrahydrocannabinol(THC) in young subjects; however, effects in aged subjects have been less well evaluated. The primary goal of the current study was to use a rat model to determine whether the cognitive effects of acute exposure to cannabis smoke differ between young and aged subjects.

Male and female young adult(6 mo.) and aged(24 mo.) Fischer 344xBrown Norway F1 hybrid rats were tested on both a PFC-dependent delayed response working memory task and a hippocampal-dependent trial-unique non-match to location(TUNL) task in touchscreen operant chambers. The delayed response task required rats to remember the location of a visual stimulus over variable delay periods ranging from 0-24 s. The TUNL task required rats to remember the location of a visual stimulus with varying degrees of discriminability from other, distractor stimuli in the absence of delays.

A semi-randomized, within-subjects experimental design was used such that each rat was exposed to smoke from burning, 0, 3, and 5 cannabis cigarettes immediately prior to test sessions in each task. In the delayed response task, acute exposure to cannabis smoke impaired accuracy in young rats but enhanced accuracy in aged rats. In contrast, in the TUNL task, cannabis smoke had no effects on performance in either age group.

Considered together, this pattern of results suggests that in aged rats, which exhibit impaired cognitive performance relative to young, cannabis smoke can enhance PFC-dependent cognition, but has no effect on hippocampus-dependent cognition.

Co-authors: Alara G├╝venli1, Erin Berthold1, Matthew Bruner1, Cesar Hernandez1, Josue Deslauriers1, Marcelo Febo1, Jennifer Bixon1, Barry Setlow1
1University of Florida

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