Modulation of serotonergic and adrenergic systems by long-term antihypertensive treatment with enalapril

Enalapril (Renitec, Merck-Sharp-Dohne, Rahway, USA) administered alone (Group I), or in combination (Group II) in a dosage normalizing blood pressure (BP) was investigated for its ability to inhibit adrenergic and serotonergic systems in a one-year study. BP normalization was achieved. Serotonin (5-hydroxytryptamine, 5HT) levels in platelet rich and poor plasma, urinary excretion of 5HT, adrenaline and noradrenaline decreased. Correlations between the changes in BP and the inhibition of serotonergic and adrenergic systems were found in the acute phase in Group I. In chronic effect the reduction of BP correlated with inhibition of the serotonergic system in both groups. Changes in adrenergic and serotonergic systems correlated in the acute phase in both groups; during chronic treatment only in Group II. It is concluded that a concurrent antihypertensive effect and the inhibition of sympathetic activity and 5HT amplifying mechanism (antiatherogenic effect) are of clinical importance for hypertension treatment and prevention of its complications.