Nicotine's effects in rats differ depending on whether the animal is male or female and lives alone or in groups, a new study conducted by the Uniformed Services University of the Health Sciences reports. These findings may have implications for human nicotine effects.

For male rats, nicotine altered activity levels and exploratory behaviors. In contrast, nicotine did not affect activity and exploratory behaviors of female rats but did alter behaviors that may reflect anxiety. Whether nicotine increased or decreased these behaviors depended on the animal's living conditions. For males that lived in groups, nicotine increased activity and exploration; for males that lived individually nicotine had the opposite effects, decreasing activity and exploration. In females, nicotine affected the amount of time female animals spent in the center of an open arena -- a situation rats are believed to find anxiety-provoking. Specifically, among females who lived in groups, nicotine increased time spent in the center, suggesting that these animals experienced reduced anxiety as a result of nicotine administration.

"Our studies with rats may reflect human sex differences in reasons for smoking. For example, women often report that they smoke to cope with emotional and social situations and to alleviate negative affect. It is striking that in our study female rats living in groups and, treated with nicotine, manifested behaviors that may indicate decreased anxiety," says Martha M. Faraday, head of the study.

The researchers reported their findings in the current issue of Nicotine & Tobacco Research.

"Men are likely to report smoking for reasons of arousal, to alleviate boredom, or to relax. Interestingly, in this experiment nicotine's effects in male rats occurred on behaviors that primarily index activity, arousal, and exploration," Faraday explains.

The scientists worked with 96 female and 96 male laboratory rats implanted with minipumps that
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Contact: Martha M. Faraday
Mfaraday@mxb.usuhs.mil
301-295-9671
Center for the Advancement of Health
30-Jun-1999