Abstract
Research demonstrates that adolescents differ from adults in their response to drugs of abuse. The aim of the present study was to examine the influence of ethanol, Δ9-tetrahydrocannabinol hydrochloride (THC), and a combination of these drugs given during adolescence on spatial memory in adolescent and adult rats. Thus, adolescent rats (postnatal day (PND) 30) were subjected to the following groups: 0.9% NaCl; 1.5 g/kg ethanol; 1.0 mg/kg THC; 1.5 g/kg ethanol + 1.0 mg/kg THC. Rats received drug injection four times at three-day intervals. One day after the last injection, half of the treated animals were tested in the Barnes maze task, whereas the remaining animals were tested on PND 70. Results show that there was a significant age effect on spatial memory in the Barnes maze task after these drug administrations. Adolescent animals demonstrated more potent deficits in the spatial learning and memory (probe trial) and in cognitive flexibility (reversal learning) than did adults. However, in adult rats that received these drugs in adolescence, memory decline was observed only after ethanol and ethanol + THC administration. Thus, our results are important in understanding the deleterious impact of THC and/or ethanol abuse during adolescence on memory function across the lifespan (adolescent versus adult).
Highlights
Adolescence is a period identified by a relatively high occurrence of substance co-use, with alcohol and cannabis as the most frequently used drugs [1]
The doses were selected based on prior work that demonstrated an impairment effect on spatial learning of ethanol doses of 1 g/kg and 2 g/kg in adolescent, but not in adult rats [20]
The effect of adolescent ethanol, THC, or the exposure of both on spatial memory acquisition in adolescent and adult rats in the Barnes maze task was studied in Experiment 1
Summary
Adolescence is a period identified by a relatively high occurrence of substance co-use, with alcohol and cannabis (marijuana) as the most frequently used drugs [1]. At present, only limited data concerning the long-lasting effects of chronic ethanol exposure during adolescence are available This is important since both the drinking pattern of adolescents or adults and the neurogenesis processes in these groups differ significantly. Of relevance is the fact that most adolescents drink repeatedly in a chronic, intermittent (“binge”) pattern and this may result in increased risk of neurotoxicity [28,29], as well as impairments of learning [30] and motor function [20,31] It potentiates the risk of addiction development in the future. The aim of our study, using the Barnes maze task, was to reveal whether THC and/or ethanol, after administration during adolescence, induced greater spatial memory impairment in adolescent (postnatal day (PND) 40) than adult (PND 70) male rats, when compared to these drugs alone
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