Effect of Phenylephrine on Cerebrovascular Regulation: A Translational Perspective

Area of Science:

• Cardiovascular Physiology
• Neurovascular Regulation

Background:

• Phenylephrine is an alpha-1 adrenergic receptor (α1R) agonist.
• α1R activation can trigger both vasoconstrictor and dilator signals.
• The effect of phenylephrine on cerebrovascular regulation is not fully understood.

Purpose of the Study:

• To investigate the impact of phenylephrine on cerebral perfusion and cerebrovascular resistance.
• To explore the role of alpha-1 adrenergic receptors in the cerebral vasculature.
• To elucidate the mechanisms underlying phenylephrine's effects on cerebral blood flow.

Main Methods:

• Retrospective analysis of human and swine data during phenylephrine infusion.
• In vivo experiments with intracarotid phenylephrine infusion in swine.
• Ex vivo studies on isolated porcine cerebral arteries.

Main Results:

• Systemic phenylephrine increased cerebrovascular resistance but did not decrease perfusion in humans and swine.
• Intracarotid phenylephrine increased cerebral perfusion under normal conditions but not during nitric oxide synthase inhibition.
• Phenylephrine induced vasoconstriction via extraluminal α1Rs and vasodilation via intraluminal α1Rs, mediated by nitric oxide.

Conclusions:

• Phenylephrine administration, systemically or intracarotidly, did not compromise cerebral perfusion.
• Increased endothelial nitric oxide signaling and reduced α1R density in distal cerebral arteries may preserve perfusion.
• Differential distribution of α1Rs and adrenergic innervation influences phenylephrine's vascular effects.