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How Does Caffeine Keep Us Awake?
With coffee and caffeinated drinks being a normal part of many people's daily routines, it has become common knowledge that caffeine results in people becoming more alert. However, aside from just knowing the cause and effect, how does caffeine work to keep us awake?
What is Adenosine?
What Makes Us Sleepy: Adenosine is a neurotransmitter released in our brains over the course of the day when ATP is broken down for our body to use as energy (Singh & McKintosh).
Adenosine's Biological Effect: When adenosine fits into our brain's adenosine receptors, it results in our neurons firing slower & slows the release of other molecules and neurotransmitters through our brain (Singh & McKintosh).
What is Caffeine?
Caffeine is very structurally similar to adenosine, and acts as an adenosine antagonist. Neurotransmitter antagonists are molecules that fit in the same receptor of another neurotransmitter without activating the receptor, essentially blocking the space and blocking the reaction (Ribeiro & Sebastião).
Blocked Receptors
There are many adenosine receptors throughout the brain, such as A1, A2A, A3, and A2B (Ribeiro & Sebastião), which the presence of caffeine moves in to block those receptors. Some of these receptors also are dopamine receptors, where adenosine’s presence normally blocks the receptor for dopamine, but with caffeine taking adenosine’s place, dopamine can now bond properly (Ribeiro & Sebastião).
What Happens Next?
With the lack of adenosine, our neurons do not slow down and the release of other neurotransmitters continue at their normal pace, allowing our brain to continue functioning in an alert state. By blocking adenosine receptors, caffeine is able to indirectly affect the release of neurotransmitters such as: norepinephrine, dopamine, acetylcholine, serotonin, glutamate, GABA, and neuropeptides (Institute of Medicine) .
Additional Effects
Aside from blocking the decrease in neuron activity, the presence of caffeine also increases intracellular concentrations of cAMP, which results in an increased heart rate and antiasthmatic behavior, which further keeps up awake and alert after consuming caffeine (Institute of Medicine).
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