Effects of Nicotine and Stress on Anxiety-Related and Depression-Related Behavior in Rats

Current cigarette use in the U.S. includes roughly 20% of civilian adults, 30% of Armed Forces personnel, and a majority of psychiatric patients. Tobacco use by American Warriors deployed to Iraq and Afghanistan is estimated at approximately 50%, despite widespread knowledge of the health risks associated with tobacco use. Two animal (rat) experiments were conducted to examine whether nicotine, the drug of addiction in tobacco, decreases anxiety-related and depression-related behavior. In Experiment 1, rats (male and female, Sprague-Dawley rats) were exposed to the Warrior Stress Paradigm (a paradigm that mimics the threat of death and environmental stressors experienced by Warriors in combat) and nicotine was delivered via SC implanted osmotic minipumps at three levels of nicotine dosages (0, 3, and 6 mg nic/kg/day). Planned comparisons between saline controls and unstressed female rats in the 6 mg nic/kg/day nicotine condition demonstrated less depression-related behavior at certain time points, yet these findings for females (and not males) were preliminary and warranted replication. There were no anxiolytic effects of nicotine in the first experiment. A second experiment used four dosages of nicotine (0, 3, 6, 9 mg nic/kg/day) and failed to find clear anti-depressant effects of nicotine. Future studies could use varying levels of Warrior stress or different predatory stressors to investigate how sex may moderate the anxiolytic or anti-depressant properties of nicotine, which may inform tobacco cessation treatment in male and female Warriors.