Good answers so far...
And tseuq, I love you
With that out of the way, I come from an adult lifetime of fasting background, so generally, much like strtman and tseuq mentioned above, I usually will go without food for at least 4-6 hours before launching any kind of vaped DMT trip. The key word here being "generally".
That being said, this is a fascinating subject to me null and I am grateful that you brought it up (yet another reason why I love you so much too!
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! )
I have never heard of the whole serotonin-DMT-vaping-fasting connection, but it makes me wonder if it doesn't have something to do with the relatively newly established scientific theory that all of our so-far-known neurotransmitters are actually produced in the gut and not the brain itself even though the brain is the particular organ that we mostly associate their actions with.
Argh, I'd like to write a lot more on this but it's getting late here and all I have is my phone for internet on the homestead, so it'll have to wait until tomorrow when I can get to the office and can get on with my laptop.
Until then kind folks, I bid you a wonderful evening/whatever-the-hell-it-is-where-you-are!
Peace
Freedom's so hard
When we are all bound by laws
Etched in the scheme of nature's own hand
Unseen by all those who fail
In their pursuit of fate