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Why is there no reflexive bradycardia when phentolamine acts on NE action?

April 26, 2017Action acts bradycardia NE phentolamine reflexive

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Why is there no reflexive bradycardia when phentolamine acts on NE action?

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In the presence of phentolamine (alpha-blocker), NE can only act on the beta-receptors. It is not as powerful on beta-receptors as EPI. It can act on the beta1-receptors in the heart to increase HR, CO & BP. It also acts on beta2-receptors to cause vasodilatation and hence decrease BP. The overall effect is no major change in BP and hence no reflex mechanism.