Assessment of alpha 2 adrenergic autoreceptor function in humans: effects of oral yohimbine.

Administration of three oral doses of yohimbine (10 mg, 15 mg, 20 mg) to eight healthy subjects resulted in significant increases in plasma free 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG). The 15 mg and 20 mg yohimbine doses induced modest increases in systolic blood pressure and autonomic symptoms such as piloerection and rhinorrhea. Marked behavioral effects such as anxiety were not observed. These results indicate that determination of the plasma MHPG response to yohimbine may be of value in assessing alpha 2 adrenergic autoreceptor function in humans.