The effects of antidepressants on the autonomic nervous system--a current investigation

Tricyclic antidepressants influence the autonomic nervous system, as is well known; and endogenous depression shows autonomic nervous symptoms besides the readily observable emotional changes. This is a report on a current investigation of the effects of antidepressants on the function of the autonomic nervous system. In a preliminary study 2 kinds of antidepressants, amitriptyline (tricyclic) and nomifensine (non-tricyclic) were administered to 20 healthy volunteers. The palmar skin potential reflex (SPR), heart rate and respiratory rate were recorded and serum dopamine-beta-hydroxylase (DBH) activity was assayed both before and after the administration of antidepressant. The results were as follows: 1. In the amitriptyline group, the spontaneous SPR and serum DBH activity decreased, and heart rate increased; and the degree of change before and after administration of the drug was statistically significant. Thus amitriptyline seems to suppress the activity of sympathetic nervous system, in addition to suppressing the functioning of the parasympathetic nervous system. 2. In the nomifensine group, spontaneous SPR and serum DBH activity tended to increase. This seems to indicate that nomifensine suppresses neither the parasympathetic nor the sympathetic nervous functions. 3. Amitriptyline and nomifensine has different effects on the sympathetic nervous system, suggesting correspondingly divergent pharmacological mechanisms for the depressive modality.