Shocking: Nicotine and the Brain

Nicotine has anti-anxiety properties, acts like a stimulant, increases cognitive function (including memory) and is connected to the emotional reward centers of our brains. No wonder it’s addictive! In fact, many clinicians agree that nicotine dependence (marked by cravings, withdrawal symptoms, and difficulty stopping tobacco use) is one of the hardest addictions to break. So how is it that nicotine affects the central nervous system so strongly?

The answer was found by studying a little-known animal called the torpedo ray.  The torpedo ray is a pretty cool animal—it has an electric organ that can generate a shock of up to 500 Volts.  If that doesn’t sound 

The torpedo ray uses the same molecules that respond to nicotine in our brains to deliver a killer shock to prey and predators. (Photo courtesy of flickr.com).

like much, know that it’s about the same amount of voltage generated by a commercial plane’s AC engine! How does the torpedo ray do it? The same way a smoker gets satisfaction from a cigarette—a molecule called the nicotinic acetylcholine receptor or nAChR.

In both the torpedo ray’s electric organ and our brains, nicotinic acetylcholine receptors (nAChRs) regulate how many charged particles flow in and out of our neurons. In the torpedo ray, this leads to a killer shock.  In our brains, this affects the level of neurotransmitters floating around, which in turn affects emotions and cognition. Normally nAChRs react with another molecule called acetylcholine that naturally occurs in the brain; but nicotine also reacts with nAChR. In fact, nicotine binds so well with nicotinic acetylcholine receptors that they were named after it! When the nicotine reacts with these receptors and binds to them, it acts like the volume dial on a stereo for neurotransmitters. Especially interesting are data that suggest that nicotine might increase levels of the neurotransmitter called dopamine in reward centers of the brain. There’s evidence that this is why people with psychiatric illnesses like anxiety and depression tend to have higher levels of nicotine dependence.

So the problem for smokers is that their brains like the nicotine too much—and respond to it too well. Too bad humans can’t harness our nicotinic activity like the torpedo ray does.

A 3D computer simulation of nAChR.

(Squire et al., ed. 2003. Fundamental

Neuroscience, 2nd ed.)

~ by mia27 on October 4, 2009.