also antagonizes several serotonin receptor subtypes: 1A (inhibitory, behavioral control), 1B (inhibitory, vasoconstriction), 1D (inhibitory, vasoconstriction), and 2B (smooth muscle contraction). Since yohimbine is an antagonist , it will decrease the effects of these receptors, thus causing excitation, vasodilation, and smooth muscle relaxation.' http://en.wikipedia.org/wiki/Yohimbine Hell,I wouldn't take it on a regular