[Effects of serotoninergic block on reactivity of systemic and pulmonary circulation in hypertensive patients]

The aim of this study was to verify the possible role of serotonin on vascular basal tone and over-reactivity in systemic and pulmonary circuits in hypertensive patients. We studied 15 hypertensive (G1) and 10 normotensive (G2) subjects. Right-side pressure and intravascular-arterial pressure measurements were obtained in baseline conditions and during alpha-adrenergic activation by cold-pressor-test (CPT), before and after intravenous injection of ketanserin 10 mg (K), an S2-receptor antagonist. Systemic and pulmonary pressures and resistances were higher in G1 than in G2 in the steady state. K induced a significant reduction of both pressures and resistances in G1, no change in systemic response to CPT in the 2 groups and a significant reduction in the pulmonary vascular reactivity to adrenergic stimulus only in G1. These data confirm the vasodilator action of serotonin-blockade. The observation of vasodilatation in pulmonary circulation is not in favor of its dependence on vascular endothelium damage. In fact the arterial endothelium lesions due to hypertension are present only in the systemic circuit. Concerning result of CPT: 1) serotonin doesn't seem responsible for vascular over-reactivity in hypertension, unchanged by K; 2) the particular pattern of pulmonary vascular contractility in G1 may be interpreted as resulting from an elective depressive action of S2-blockade, depending on a different distribution of S1 and S2 receptors in the two circuits.