Nicotine is the addictive chemical in tobacco smoke and e-cigarette vapors. And doctors say a teen's brain is no place for it to end up. Nicotine can reach the brain within seven seconds of smoking a cigar, cigarette or electronic cigarette
The area of the brain responsible for emotions and controlling our wild impulses is known as the prefrontal cortex(前额叶皮层). It's very easily affected by nicotine, research shows. This is especially true for young people, because this part of the brain doesn't finish developing until about age 25.
Nicotine acts like a key to unlocking special receptor(感受器)molecules on the outside of cells in the brain, including those in the prefrontal cortex. Nicotine causes these cells to release signaling molecules, such as dopamine(多巴胺). These chemical signals travel across a gap between nerve cells. When they reach the neighboring nerve cell, they release their "message And it makes users get a feel-good high.
But after repeated exposure to nicotine, those brain cells can change. The effect of these changes is to reduce the body's ability to release its own, natural pleasure-giving chemicals.
Meanwhile, the brains of teens who smoke or vape may create more receptors to handle the flood of nicotine they have come to expect. As the number of receptors increases, teens will need more nicotine to get the same high. That makes nicotine users seek hit after hit. In teens, this can provoke side effects. For instance, it can make it hard for them to stay focused. It might also trigger depression or anxiety, research suggests
Some of the negative effects of nicotine on the young brain will fade with time—if exposure ends.Others, however, may persist. For instance, brain scientists at VU University Amsterdam found that exposing adolescent rats to nicotine increased their aggressive behavior. It made them a bit more reckless than usual. It also made it harder for them to focus their attention—even later, as adults
No one is sure that the same thing happens in humans, but that's exactly what worries Garry Sigman."Exposing the developing adolescent brain to nicotine could lead to a high risk of lifelong addiction,"he explains.