Medical opinion here...
From what we know of pain, there are few things that 'stop' impulses. Short of exogenous chemicals (drugs) your body has a limited arsenal of things it can do.
Adrenaline (or, as well call it, Epinepherine... also coupled with dopamine and norepinepherine) has no effect on pain sensation. What happens is that the 'adrenaline' causes some endorphins to release. This causes the same effect of taking an analgesic... less pain. However, its only effective for a short period of time AND it can be overrided.
Your 'tazer' (sp? is it taser? i dunno..)... well, what that does is cause your nervous system to suddenly depolarize and fire wildly, causing muscle weakness, paralysis, and... pain! It overrides the endorphin effect. As will pressure points.
Your endorphins are also what are responsible for the 'runner's high' some people experience.
Now, after this brief surge of endorphins wears off, your body has been poppin out Enkephalins. Same type of deal, but these do not remove pain, they change its perception. This is the 'dull throbbing, pain you sometimes experience.
The function of these chemical mediators in the body is 'fight-or-flight' for endorphins. They will get you 'through the worst' or at least away from that animal about to kill you. The Enkephalins will allow you to seek help post-incident without being overcome by pain, but it allows you to KNOW you have pain still. Interesting survival adaption.
However... as said... electricity works well at overcoming it. Pepper-spray works well too, since it attacks an especially sensitive pain receptor (caspin receptors). Pressure points are something of a mystery, but i would imagine they somehow bypass the mechanism of pain suppressed by endorphins.