Adenosine is a waste product of neurons and it is a potent nervous system depressant which is why if we don’t sleep for a long time we hallucinate, start to feel cold, and feel tired. We feel like we’re drugged because we kind of are. It also increases sleep pressure. Unlike other areas of the body the brain has no way of flushing out the adenosine unless we sleep which activates the glymphatic system. if we don’t sleep the adenosine keeps accumulating and it can kill us in a similar way an od of sleeping pills can.
Adenosine is not a “waste product of neurons” in the sense it’s being painted. It’s a byproduct of energy production in all our cells, and what it does depends on the derivative - for example adenosine triphosphate (ATP) is used by the mitochondria in our cells for energy production! It then degrades into adenosine monophosphate (AMP) and from there into the CNS-depressing adenosine (or, it can be upregulated back “up the chain” by adding another phosphor to it).
As plain adenosine it can depress the central nervous system, resulting in feeling sleepy, slowing heart rate, etc, but adenosine levels are regulated closely by the body and the idea they can “build up until we die” due to lack of sleep is patently ridiculous. This article is a gross oversimplification that demonises a critical compound for no reason.
This article covers the detrimental results of adenosine overproduction in the body: https://pmc.ncbi.nlm.nih.gov/articles/PMC6398520/
While Wikipedia describes the compound more generally: https://en.wikipedia.org/wiki/Adenosine
