Although nicotine in regular cigarettes is just one component of
smoke from tobacco leaves, nicotine in e-cigarettes is typically extracted
from tobacco leaves in the lab, which is how it can be delivered without
many of the other harmful compounds found in regular cigarettes.
What makes nicotine so addictive? Within roughly 10 seconds, nicotine moves straight from a regular cigarette to the brain. There, it competes with a chemical called acetylcholine (Fig. 1). Acetylcholine is a
neurotransmitter, a molecule that relays messages between nerve cells,
called neurons. The brain uses neurotransmitters to tell your heart to
beat, your lungs to breathe, and your stomach to digest. Neurotransmitters can also affect mood, sleep, concentration, and weight.
In the brain, acetylcholine binds to special molecules, called recep-
tors, on the surface of a neuron. Once acetylcholine binds to a recep-
tor, the receptor changes its shape and allows sodium ions to flow
inside the neuron. This flow of ions is how neurons “talk” to each
other. The flow of ions also causes the release of other neurotransmit-
ters and hormones that affect your mood, your memory, and even your
Because the chemical structures of nicotine and acetylcholine are
similar, nicotine can bind to the same receptors that acetylcholine does;
in chemical terms, both molecules have an affinity for the same receptors. In fact, some acetylcholine receptors are called nicotinic receptors,
for their ability to bind nicotine! In Fig. 2, the similar parts of the acetylcholine and nicotine structures are shown in red.
Acetylcholine binds to its receptor through its trimethylammonium
group, which consists of a nitrogen atom bound to three methyl groups
Nicotine binds to the same receptor using a group of atoms
similar to acetylcholine’s trimethylammonium group. It is posi-
tively charged and contains a nitrogen atom bound to one methyl
group and two –CH2 groups (Fig. 2).
By binding to acetylcholine receptors, nicotine stimulates the
adrenal glands to produce epinephrine, a hormone and neurotransmitter also known as adrenaline. This chemical increases
heart rate and blood pressure while constricting blood vessels,
which explains why smoking helps people feel energized and
alert. It also stimulates the production of dopamine, a neurotransmitter that controls the brain’s pleasure center, which
keeps smokers coming back for more.
Nicotine’s effects on the body
Normally, your body carefully monitors the concentration of
acetylcholine, to ensure that you are receiving the right amount of
this chemical. Your cells can produce more acetylcholine, store it,
release it, or break it down, depending on how much you need at
a given time. For example, when you are concentrating hard on a
test question, lifting weights, or facing off with a scary figure in a
dark alley, the cells in your body will release more acetylcholine.
When you are relaxing with friends or watching your favorite TV
show, your cells can work on breaking down
unneeded acetylcholine molecules that are
loose in the body and rebuilding stores for the
next time the chemical is needed. When nicotine binds to nicotinic receptors, this system
doesn’t work as well, because nicotine is not
regulated by the body.
Although neurons typically release small
amounts of acetylcholine in a regulated manner, nicotine activates neurons in many different regions of the brain simultaneously. All of
this unregulated stimulation causes cells to
release acetylcholine, leading to heightened
activity throughout the brain—whether the
situation requires it or not.
ChemMatters | FEBRUARY/MARCH 2016 17
Figure 1. Neurons are nerve cells that carry messages. (a) A neuron is made up
of three parts: the cell body, which contains the nucleus and other organelles;
dendrites, which receive nerve impulses from other cells; and axons, which pass
the nerve impulses on to other cells. (b) Neurons use neurotransmitters, such as
acetylcholine, to send messages to each other. Nicotine imitates acetylcholine,
sending the same messages—but in much greater quantities.
Acetylcholinereceptors Nicotine molecule
Figure 2. The chemical structures of acetylcholine and nicotine. The similar
parts of the molecules are highlighted in red.