The disruption of the pH gradient is the central part of amphetamine's mechanism of action. Dopamine is stored inside vesicles inside presynaptic neurons. By disrupting the proton gradient between the lipid bilayer of these vesicles, dopamine is allowed to leak out and released into the synaptic cleft.

Which is part of the reason why amphetamine increases extracellular dopamine. Unfortunately, instead of being nicely packaged in vesicles, now some of these dopamine are floating around in the cytosol, making them susceptible to autooxidation to quinones, nasty stuff.

Unfortunately, most of these research are behind paywall but that is the little lf what I remembered from all the reading years ago.

thanks for the response, I'll look into it through my uni research portal