Urinary excretion of noradrenaline after treatment with alpha-methyldopa: inhibition by a central nervous mechanism

Hypertension and left ventricular hypertrophy: is drug therapy beneficial?

Left ventricular hypertrophy (LVH) is a consequence of long-standing hypertension and is considered to be an independent risk factor for cardiovascular morbidity and mortality. Several antihypertensive agents are capable of inducing regression of LVH, but it is not known which class of drugs is most effective. The impact of drug-induced reversal of hypertrophy on ventricular function remains a controversial issue. Furthermore, the long-term clinical benefits of LVH regression have yet to be documented. Controversies also exist regarding the clinical outcomes associated with drug-induced LVH regression.

Time course of regression of left ventricular hypertrophy in treated hypertensive patients

In a prospective study, 32 hypertensive patients with echocardiographic evidence of left ventricular hypertrophy were treated with methyldopa, hydrochlorothiazide, or methyldopa and hydrochlorothiazide combined. Echocardiograms and electrocardiograms were obtained in each of the 32 patients before treatment, at the point of initial blood pressure control, and then one, three, and six months thereafter; in 27 patients these studies were also obtained after 12 and 18 months. Left ventricular end-diastolic posterior wall thickness decreased in seven patients whose blood pressure was controlled with methyldopa alone (p less than 0.01) and in 17 patients whose blood pressure was controlled with methyldopa and hydrochlorothiazide combined (p less than 0.01); in both groups, the reduction in left ventricular posterior wall thickness at end-diastole was apparent one month after blood pressure control was established (p less than 0.05). In contrast, no significant reduction in left ventricular posterior wall thickness at end-diastole was observed in eight patients who had equivalent control of blood pressure with hydrochlorothiazide alone (p = 0.34). During the 18-month follow-up period, ventricular septal thickness at end-diastole decreased in the group treated with methyldopa and hydrochlorothiazide combined (p = 0.03); whereas, ventricular septal thickness at end-diastole appeared to increase in the group treated with hydrochlorothiazide alone (p less than 0.01). These results suggest that evidence of regression of left ventricular hypertrophy may be detected as early as one month after blood pressure is controlled with methyldopa or methyldopa and hydrochlorothiazide combined; whereas, long-term control of hypertension with hydrochlorothiazide alone was not associated with evidence of regression of left ventricular hypertrophy. Although the patient number are small, these data suggest that there are differences in the long-term effects of diuretics and sympatholytic drugs on left ventricular anatomy, which may, in part, relate to divergent effects on the sympathetic nervous system.

6-hydroxydopamine destruction of central adrenergic neurones prevents or reverses developing DOCA-salt hypertension in rats

The role of brain catecholaminergic neurones in the pathogenesis of DOCA-salt hypertension in the rat was investigated by selective depletion of central catecholamines using intraventricular or intracisternal administration of 6-hydroxydopamine (6-OHDA). Only the intraventricular injections prevented the development of hypertension. In addition, intraventricular 6-OHDA reversed the hypertension produced by two weeks but not six weeks of DOCA-salt treatment. The ability of intraventricular injections of 6-OHDA to prevent or reverse DOCA-salt hypertension while intracisternal injections do not, appears to be related to the greater depletion of brain catecholamines produced by the intraventricular injections. Only in the spinal cord and in the locus coeruleus were the norepinephrine contents depleted equally by either injection route. These findings suggest that central catecholaminergic neurones other than those originating in the locus coeruleus or descending in the spinal cord are important in the initiation, but not in the long term maintenance, of DOCA-salt hypertension. The influence of the central catecholamine neurons involved in the development of DOCA-salt hypertension might be mediated neurally via nonadrenergic pathways or hormonally via the brain-pituitary-endocrine system.