Plasma neurotransmitters, blood pressure, and heart rate during supine-resting, orthostasis, and moderate exercise conditions in major depressed patients.

Major depressed patients showed greater heart rate, noradrenaline, and free-serotonin values than normal. Conversely, platelet-serotonin values in major depressed patients were significantly lower than normal. Patients registered the normal differential blood pressure reduction during orthostasis. They also revealed progressive and significantly higher heart rate rises during orthostasis and exercise periods, when compared to normals. Whereas noradrenaline showed maximal rises during the two last periods, adrenaline only showed small but significant increase during exercise. The analysis of correlations, together with the above data, suggests that major depressed patients register maximal neural sympathetic activity as well as adrenal glands sympathetic hypoactivity. In addition, these patients show hyperparasympathetic activity, as reflected by the free-serotonin profile. Finally, the fact that both the Hamilton Depression Rating Scale and the self-rating Beck Depression Inventory correlated positively with noradrenaline/adrenaline ratio and free-serotonin values strongly suggests that both neural sympathetic and cholinergic mechanisms are involved in major depression.