Ahhh.......now I understand your question!!
Well I personally believe that the rush is non-present due to the fact that pure meth triggers precisely one hormone:norepinephrine. And Has a super high perifial effect on ones neurons.
And the rsh actually comes from seratonin flooding ones pleasure receptors.
cocaine is a pure seratonin trigger.
Hence, its cherished buzz when one injects it into their bloodstream and straight to ones brain.(man-oh-man!! I love and hate cocaine!!)
Then as the seratonin is told to stop by running out of its trigger the brain and sense of wellbeing experiences a horrrible hangover and fear of coming down from Heaven above so high in the sky!!
Wellebutrin is a dopamine drug. And itis a miserable drug to take from personal experience.
So dopamine can't be another possible factor in the rush crank produces.
Rather, its the following three:
1)norepinephrine
2)seratonin
3)endorphin(orgasms are produced by endorphins)
Why crank and its so-called impurities triggers these wonderful triplets of pleasure is probably a mystery never solved.
Because I've done what some called glass and it was just like Desoxyn......boring and no desire to sit down after a shot and smile for an hour or three!!
Nice! good question Frey

You really thought provoked my mind on this one in attempting to answer.
Kinda reminds me of Worlcks' PM's at Chemhead......provocative and deep in substance. And yet simple and easy to comprehend at the same time.

<----------me waiting on a rush to come after shooting some Desoxyn.
hehe.....