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How does Caffeine Work in the Brain?
Drug
molecules generally work by interacting with receptors on the
surface of cells or enzymes (which regulate the rate of chemical
reactions) within cells (see how
do drugs work for details). Receptor and enzyme molecules
have a specific three-dimensional structure which allows only
substances that fit precisely to attach to it. This is often referred
to as a lock and key model. This is the case for the caffeine
molecule in coffee.
Caffeine is
the active ingredient in coffee. It is a bitter, white crystalline
xanthine alkaloid that acts as a stimulant drug. Regular use of
caffeine can cause mild physical dependence although it will not
threaten your physical, social, or economic health the way addictive
drugs do. But caffeine withdrawal can make for a few bad days.
WHAT IS THE MOLECULAR MECHANISM
OF THE CAFFEINE MOLECULE?
Because
the caffeine molecule is both water-soluble and lipid-soluble, it readily crosses
the blood–brain barrier that separates the bloodstream from the
interior of the brain. Once in the brain, the principal mode of
action is as a nonselective antagonist of adenosine receptors
(in other words, an agent that reduces the effects of adenosine).
The caffeine
molecule is structurally similar to the adenosine
molecule, and is capable of binding to adenosine receptors
on the surface of cells without activating them, thereby acting
as a competitive inhibitor.
Below shows the static molecular structure for the caffeine molecule on the left and adenosine molecule on the right.
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CAFFEINE
CHEMICAL STRUCTURE
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ADENOSINE
CHEMICAL STRUCTURE
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CAFFEINE
MOLECULE
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ADENOSINE
MOLECULE
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Above are Jsmol applets for caffeine and adenosine. They are shown in stick model. To use Jsmol click on your right mouse button over the rotating image. You can go down to spin (turn off) to stop the motion.
How caffeine works on the A2 receptor protein
The
A2 receptor protein is a member of the G protein-coupled receptor (GPCR)
family which possess seven transmembrane alpha helices.
The
A2A receptor is responsible for regulating myocardial blood flow by
vasodilating the coronary arteries, which increases blood flow to the
myocardium, but may lead to hypotension. Just as in A1 receptors, this
normally serves as a protective mechanism, but may be destructive in
altered cardiac function.
Caffeine
competitively inhibits different adenosine receptors and their associated
G protein to make a person feel alert. A mild stimulant of the central
nervous system, caffeine also stimulates cardiac muscle, relaxes smooth
muscle, increases gastric secretions, and produces diuresis.
The
A2A receptor also has important roles in the regulation of glutamate
and dopamine release in the brain, making it a potential therapeutic
target for the treatment of conditions such as insomnia, pain, depression,
drug addiction and Parkinson's disease.
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pdb
fle: 3RFM (shown using the Jmol Applet)
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A2 Adenosine
receptor molecule (ribbon model) in complex with Caffeine shown as colored grey in CPK
Try this to change Caffeine molecule to color by atom type:
Right mouse --> scroll to Color -->Atoms --> By scheme --> element (CPK)
pdf file: 3RFM |
Selected
Readings
Health
effects of caffeine
Structure
of the adenosine A(2A) receptor in complex with ZM241385 and the xanthines
XAC and caffeine.
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all of this text has been obtained from Wikipedia, the free encyclopedia.
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