Sympathetic nervous system and hypertension. Therapeutic perspectives

The sympathetic nervous system has a key role in the physiological regulation of the circulation and may also mediate some of the factors that cause or sustain clinical hypertension. Most classes of antihypertensive drugs produce at least part of their effects by inhibitory actions on the sympathetic pathways. The centrally acting agents and the peripheral alpha-adrenergic blockers are the most specific currently used sympathetic inhibitors. The available alpha-blockers, prazosin and terazosin, effectively reduce blood pressure when used as monotherapy or in combination with other antihypertensive drugs. When given once daily, the actions of terazosin persist throughout the full 24-hour period, including the important midmorning hours when there may be heightened sympathetic activity. The incidence of symptomatic adverse effects with the alpha-blockers is low. Because they specifically block peripheral alpha-receptor-mediated vasoconstriction, the alpha-blockers decrease total peripheral resistance at rest and do not antagonize the appropriate vasodilatory responses to exercise. They maintain or increase blood flow in regional circulations; cerebral blood flow in elderly patients is unchanged despite significant decreases in systemic blood pressure. In contrast to other drug classes that can adversely affect the lipid profile, the alpha-blockers slightly decrease total cholesterol concentrations. Recent studies also have shown that terazosin and prazosin can promote decreases in echocardiographically measured left ventricular wall thickness and muscle mass in hypertensive patients with left ventricular hypertrophy. Thus, this type of sympathetic blockade not only produces antihypertensive effects, but additionally may have a beneficial impact upon other cardiovascular risk factors.