1 The effect of captopril on autonomic reflex functions has been investigated in fifteen patients with essential hypertension by examining their responses to tests of baroreceptor function (Valsalva's manoeuvre and upright posture), sympathetic nervous system reactivity (cold pressor and mental stress tests) and parasympathetic reactivity (diving test) before and after 3 weeks' treatment with captopril. 2 Captopril significantly reduced arterial blood pressure and resting heart rate but did not affect cardiovascular responses to Valsalva's manoeuvre, upright posture, cold pressor and mental stress tests. 3 The bradycardia associated with the diving reflex test was significantly enhanced by captopril (P less than 0.01). 4 These results indicate that treatment with captopril is associated with increased parasympathetic tone but without inhibition of baroreceptor or sympathetic reflexes.

Bromocriptine (2.5 mg/day orally) produced a significant fall in supine mean arterial pressure in nine hypertensive haemodialysis patients with high serum prolactin levels, without causing significant changes in heart rate. On bromocriptine, there was a significant decrease in the mean value of both serum prolactin and plasma noradrenaline, without significant changes in the mean value of plasma renin activity. A significant relationship was found between the changes in supine plasma noradrenaline and the changes in supine mean arterial pressure induced by bromocriptine. The increase in mean arterial pressure in response to the tilt test was greater on bromocriptine than on placebo although the changes in plasma noradrenaline were reduced by bromocriptine. Similar results were observed during the cold pressor test. These findings suggest that the arterial pressure-lowering effect of bromocriptine is related to the reduction in sympathetic out-flow. The parallel decrease in serum prolactin raises the question of the possible involvement of dopaminergic mechanisms in the development of hypertension in our patients. Moreover, bromocriptine seems to enhance the vascular response to endogenous noradrenaline.

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This paper compares renal scintigraphy (RS) with renal vein renin activity (RVRA), intravenous pyelography (IVP), and peripheral plasma renin activity (pPRA) in a population of hypertensive subjects with suspect renovascular hypertension (RVH), of whom 30 underwent surgery, in order to evaluate (a) screening ability of RS for RVH, and (b) surgical prognosis of RS for RVH. RS agreed with arteriographic findings of arterial stenosis in 91% of patients and proved more sensitive as a screening test than IVP and pPRA. The false-negative rate of RS was 9% and the false-positive rate was 10%. In the patients who underwent surgery RS was positive in 89% and RVRA in 85% of those who benefited from surgery. In this series false-negatives for RS occurred only in the presence of extensive collateral circulation, where RVRA also gave the same result. In patients who had been operated on, the sensitivity and specificity of RS, compared to RVRA, were very high. Our work supports the view that RS is a good screening test in RVH; moreover, it seems to be as accurate as RVRA as a surgical prognostic method for curable RVH.