overweight.com,
yohimbine is a A2 antagonist (it binds to the A2 and has no action, while stoppping both NE and most likely Estradiol and estrone(though this is not entirely clear)). This stops downregulation of NE production and may decrease (over time) the # of A2 (not entirely clear)
There are A2 receptors all parts (to on extent or another) of your body, however you want to achieve high concentrations of them in the areas where you have A2 dense fat.
This is the reason that topical admin is superior to oral, with oral you get systemic effects(side effects) at much lower doses, you get a quick release and metabolism of the yohimbine, and thus you get limited fat burning.
With topical admin (given the right carriers and penetration enhancers) you can acheive localized concentrations and a systemic release that less intense and extended (higher doses can be used to saturate local A2).
WHY is blocking the A2 important? if the A2 is not blocked, the release of NE is rapidly downregulated and local lipolysis inhibited. This the main reason for stubborn fat pockets which unfortunately for most women are influenced heavily by estrogen exposure. btw- some evidence that E itself inhibits lipolysis in A2 rich areas. Of course you have the viscious cycle of fat being a peripheral producer of aromatase.
that is a general overview... there are some fine points with repsect to estrogen interaction that are still unclear. However the anecdotal evidence, is very clear that yohimbine is effective in "helping" (you still have to do some work) to release fats from A2 (estrogenic- though some have A2 density genetically) pockets.
peace