In article <3u5cvj$d5n at pipe3.nyc.pipeline.com> Wise Young,
wisey at nyc.pipeline.com writes:
>Besides its role in ATP, adenosine is a kind of neurotransmitter and has
>vasoactive properties. It acts on the same receptors as does caffeine.
It's true that adenosine receptors are sensitive to caffeine (and so are
the cyclic nucleotide hydrolyzing enzymes that break down cyclic
adenosine monophosphate (cAMP). But in both of these cases, caffeine acts
to inhibit the function of these proteins. The adenosine's action on its
receptor causes the inhibition of neurotransmitter release from
presynaptic nerve terminals, and is usually associated with depression of
transmission in brain slice experiments, so I don't understand how this
action of adenosine would reduce lethargy, memory loss or fatigue.
Adenosine is the product of the breakdown of cAMP, so maybe excess
adenosine slows down this enzyme by shifting the chemical equilibrium
backwards to favor a build up of cAMP. cAMP is an important second
messenger involved in all kinds of cellular processes, so elevating it
may help with fatigue, memory loss, etc... Caffeine should do this, too.
But my guess would be that having a lot of adenosine floating around
would cause more depression (of transmission) than an increase in cAMP.
What I'm really curious about is how the adenosine gets to wherever it's
acting, after taking it orally. I'd be inclined to think that it would be
broken down in the stomach. If not, then I'd be equally inclined to think
that it would have a hard time crossing the blood/brain barrier.
I remain perplexed. But, hey, if it works, go with it!