Key result
IV bretylium and guanethidine selectively enhance the pressor response to noradrenaline over angiotensin.
Why the study?
The mechanisms by which bretylium and guanethidine potentiate the pressor response to noradrenaline in humans were unclear, particularly whether this was due to reflex blockade or arteriolar smooth muscle sensitization.
May support arteriolar smooth muscle sensitization by bretylium and guanethidine; leaves open demonstration and relevance in clinical settings.
In normal human subjects the intravenous administration of bretylium and guanethidine rapidly increased the pressor response to intravenous infusions of noradrenaline, while the response to angiotensin was little or not affected. This result suggests that potentiation of noradrenaline by bretylium and guanethidine is not simply due to block of homeostatic reflexes, but is due to sensitization of arteriolar smooth muscle. But we, like others, have failed to demonstrate such an effect in man when measuring changes in blood flow during intra-arterial infusions of noradrenaline.
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R E Nagle (1963) studied Normal human subjects. Bretylium and guanethidine was evaluated on Pressor response to intravenous infusions of noradrenaline and angiotensin. Intravenous bretylium and guanethidine rapidly increased the pressor response to intravenous noradrenaline, while the response to angiotensin was little or not affected.
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