Hemodynamic effects of guanfacine in essential hypertension.

Hemodynamic evaluation of three men and eight women aged 20 to 58 years (mean, 44 years) with essential hypertension was performed before and after a single dose of guanfacine and before and after long-term administration of the drug, which is a stimulant of central alpha-adrenergic receptors. Mean (+/- SE) recordings of blood pressure before catheterization were 168/115 +/- 6/3 mmHg when supine and 168/112 +/- 8/4 mmHg when standing. Within two hours of oral administration of 3 mg of guanfacine, the heart rate decreased from a mean of 77 +/- 2 to 69 +/- 3 beats/min (P less than 0.

Sympathetic nervous system response to graded exercise: effect of beta-blockade.

This study compares the sympathetic nervous system response to graded exercise in normotensive and essential hypertensive subjects with and without beta-adrenergic blockade. Blood pressure (BP), heart rate, and plasma norepinephrine (NE), epinephrine (E), and dopamine (DA) were measured just before starting the exercise (Pre-Ex), in the submaximal exercise (Sub-max),and after 8 minutes rest (Post-Ex). On placebo, Sub-max induced in both normotensives and hypertensives a similar increase in NE and E plasma levels.