Figure 728

Peripheral adrenergic neuronal blocking agents. Peripheral adrenergic neuronal blocking agents are selectively concentrated in the adren-ergic nerve terminal by an active transport mechanism, or "norepinephrine pump" [6,9]. They act by interfering with the release of norepinephrine (NE) from neuronal storage sites in response to nerve stimulation and by depleting norepinephrine from nerve endings. Acutely, cardiac output is reduced, caused by diminished venous return and by blockade of sympathetic (-adrenergic effects on the heart; peripheral resistance is unchanged. Following chronic therapy, peripheral resistance is decreased, along with modest decreases in heart rate and cardiac output.

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