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"Drinking caffeine is thus like putting a block of wood under one of the brain's primary brake pedals."

— Braun, Stephen

Author

Braun, Stephen

Work Title

Buzz: The Science and Lore of Alcohol and Caffeine

Place of Publication

Oxford

Publisher

Oxford University Press

Date

1996

Metaphor

"Drinking caffeine is thus like putting a block of wood under one of the brain's primary brake pedals."

Metaphor in Context

Despite this aggressive attraction to the adenosine receptor, caffeine doesn't actually make a perfect fit. And this makes all the difference. If caffeine mimicked adenosine exactly it would be a depressant, not a stimulant: it would simply exacerbate and extend adenosine's natural inhibition in the brain. But when caffeine binds to the adenosine receptor, the resulting shift in the shape of the receptor molecule is slightly different from the warping that occurs when adenosine itself binds. As a result, the chemical chain reaction normally initiated by adenosine isn't triggered by caffeine. Caffeine is an impostor: it binds with gusto, but fails to launch the all-important quieting message delivered by adenosine. Drinking caffeine is thus like putting a block of wood under one of the brain's primary brake pedals. Caffeine is an indirect stimulant: brain activity speeds up because it can't slow down. By itself, then, caffeine can't stimulate anything. It can only clear the way for the brain's own stimulants--neurotransmitters such as glutamate, dopamine, and the endorphins--to do their job. You can, therefore, get wired only to the extent that your natural excitatory neurotransmitters support it.
(pp. 129-130)