Research Area: Endocrinology Biological Activity: Yohimbine(Antagonil) has been used as a mydriatic and in the treatment of impotence. It is also alleged to be an aphrodisiac. Yohimbine is a pre-synaptic alpha 2-adrenergic blocking agent. Yohimbine may exert its beneficial effect on erectile ability through blockade of central alpha 2-adrenergic receptors producing an increase in sympathetic drive secondary to an increase in norepinephrine release and in firing rate of cells in the brain noradrenergic nuclei. [1]