1.   In the study, researchers found that rats that could get nicotine by pressing a lever gave themselves enough to maintain certain levels of it in their brains.

2.   It said in a statement that other factors, besides varying the amount of available nicotine, were also important in determining how much nicotine a user got.

3.   These patients use the gum or patch to get their nicotine without smoking and, they hope, wean themselves off of their nicotine needs.

4.   The researchers cautioned that smoking is a bad way to get medical nicotine.