Definition of "adenosine"

Caffeine acts as an antagonist at receptors in the brain for one of the chemical messengers called adenosine.

2001, Leslie Iversen, Drugs: A Very Short Introduction, Oxford, page 82

Think of adenosine as a chemical barometer that continuously registers the amount of elapsed time since you woke up this morning.

2017, Matthew Walker, Why We Sleep, Penguin, published 2018, page 27

SAM: Readings confirmed. Based on the levels of adenosine in your system, the neural implant is functioning properly.

2017, BioWare, Mass Effect: Andromeda, Redwood City: Electronic Arts, PC, scene: Hyperion

Adenosine levels can be quickly righted after a few nights of good sleep, however.

2022 June 24, Oliver Whang, “The Sleep Debt Collector Is Here”, in The New York Times‎