My experience was caused by 5-mapb & I suspect might have been more severe than those suffered by even the heaviest MDMA users. I was effectively frozen in space, unable to move physically AT ALL without setting off a continuous series of these, as you describe, entire body/brain zaps. I am not a woos, I have been through some serious things in my time but this was quite simply unbearable. Along with all my Zap symptoms & I was also by turns depressed & tearful, suicidal, infuriated, hysterical then back to tearful again. Yeah, I was a real party! My girlfriend deserves a fucking medal! 3 days I was like this & emotionally, I cannot yet say, 6 months later, that I am 100% recovered & yes, I still get the ocassional zap.
The survivors high I got after recovering from this I can tell you rivalled any MDMA high I've EVER enjoyed & it lasted a fucking WEEK. I was in heaven to be alive!
First day out though, after 3 days trapped in bed, just getting out the block & over to the corner shop, I had to take every step with care, I had trouble looking for traffic coz turning my head quickly set off the zaps.
I am now prone to brain zaps & my time with drugs such as MDMA might be at an end. Fingers crossed, with infinite patience & caution, one day I might try again...