Sympathetic outflow to muscles during treatment of hypertension with metoprolol.

Microelectrode recordings of multiunit sympathetic vasoconstrictor activity were made in muscle branches of the peroneal nerve in patients with essential hypertension before and during long-term treatment with the cardioselective beta-adrenergic receptor antagonist metoprolol. Nerve activity was quantified by counting the number of sympathetic bursts in the mean voltage neurogram. Metoprolol treatment lowered blood pressure and heart rate in all subjects. During long-term treatment, nerve activity was reduced both when compared to the level of activity after the first dose of the drug (p less than 0.01) and when compared to the control level before treatment (p less than 0.05). It is suggested that the reduction of sympathetic vasoconstrictor outflow to muscles contributed to the blood pressure reduction.