Effect of Alcohol and Tobacco Smoke on Long-Term Memory and Cell Proliferation in the Hippocampus of Rats

Introduction: Alcohol is frequently used in combination with tobacco and few studies explore interactions between these two drugs of abuse. Here, we evaluated the effect of chronic alcohol administration and concomitant exposure to tobacco smoke on long-term memory and on cell proliferation in the hippocampus of rats. Methods: Forty male Wistar rats were assigned to 4 groups and treated with alcohol (2 g/kg by gavage) and/or exposed to tobacco smoke (from 6 cigarettes, by inhalation) twice a day (at 9AM and 2 PM) for 30 days. Long-term memory was evaluated in the inhibitory avoidance test and hippocampal cell proliferation was analyzed for BrDU immunohistochemistry. Results: Our results showed that alcohol, tobacco smoke or their combination improved the long-term memory evaluated by the memory index in rats. Moreover, alcohol and tobacco coadministration decreased BrdU-labeled cells by 60% when compared to the control group, while alcohol treatment decreased labeled cells by 40%. The tobacco group showed a non-significant 26% decrease in labeled cells compared to the control group. Conclusions: Chronic alcohol and tobacco coadministration improves the long-term memory in rats in the inhibitory avoidance test. However, coadministration decreases the cell proliferation in the hippocampus of rats, suggesting a deleterious effect by the combined use of these drugs of abuse.