beta-Endorphin and essential hypertension: importance of the clonidine-naloxone interaction.

Analysis of the effect of naloxone (0.4 mg iv.) on clonidine hypotension in 80 patients with essential hypertension revealed that two groups could be separated.

Effects of clonidine and guanfacine in essential hypertension.

Daily doses of 0.3 mg clonidine and 3 mg guanfacine were equiactive in decreasing blood pressure and heart rate in 17 subjects with essential hypertension. Clonidine decreased cardiac output and guanfacine decreased total peripheral resistance, while clonidine had no effect on stroke volume but guanfacine increased it.

Beta-endorphin contributes to the antihypertensive effect of clonidine in a subset of patients with essential hypertension.

Naloxone [0.4 mg iv.] increased blood pressure and heart rate of 13 clonidine-treated [0.

Reversal by naloxone of the antihypertensive action of clonidine: involvement of the sympathetic nervous system.

The effects of clonidine, naloxone, and their combination on arterial blood pressure (BP), heart rate (HR), and hemodynamic and biochemical parameters were examined in 29 patients with essential hypertension. Treatment for 3 days with 0.3 mg/day clonidine reduced BP and HR, and these effects were quickly reversed by a single injection of 0.

Diurnal rhythm of beta endorphin in normotensive and hypertensive patients: the effect of clonidine.

Diurnal rhythm of plasma beta endorphin was established with the highest level in the morning and the lowest one at midnight in normotensive subjects and also in patients with essential hypertension. Clonidine (300 micrograms daily) significantly increased plasma beta endorphin concentrations only in the hypertensive patients. The significant linear correlation between the increase in plasma beta endorphin concentration and the decrease in blood pressure (both systolic and diastolic) in these patients may point to the role of this endogenous opioid in the antihypertensive action of clonidine.

Effect of prazosin and oxprenolol on plasma renin activity and blood pressure in patients with essential hypertension.

48 patients with normal-renin essential hypertension were treated with prazosin alone or in combination with oxprenolol. 1 h after a single dose of 2 mg prazosin tachycardia and a decrease in blood pressure developed. Renin activity in the peripheral plasma (PRA) increased from 1.