Venous plasma epinephrine levels and the symptoms of stress.

It is widely believed that increases in circulating epinephrine (adrenaline) levels contribute substantially to the physical sensations (symptoms) associated with stress. Using a drug discrimination choice procedure, it was demonstrated that the plasma epinephrine levels at which healthy human subjects reliably discriminate between infusions of epinephrine and saline are higher than the levels typically observed in situations of mental stress. Choice of epinephrine versus saline was strongly associated with a subjective perception of a change in the action of the heart, but only moderately associated with the venous plasma epinephrine levels attained and only weakly associated with actual changes in heart rate and peripheral blood pressure. These results imply that epinephrine release from the adrenal gland plays at most a small role in the production of the somatic symptoms of mental stress.