The unopposed alpha-stimulation phenomenon: What is the role of beta-blockers?

John R Richards, Howard E. McKinney, Bernard Silke

Research output: Chapter in Book/Report/Conference proceedingChapter


The experimental phenomenon of unopposed α-stimulation (UAS) is essentially the increase in systemic vascular resistance, peripheral blood pressure, and/or coronary arterial vasoconstriction after administration of a β-blocker. The explanations for the putative physiological mechanisms behind this phenomenon seem straightforward and plausible. However, upon further investigation, the autonomic nervous system regulation of blood pressure, heart rate, and coronary epicardial and microvascular blood flow is based on a complex relationship among the sympathetic α- and β-adrenergic system, parasympathetic acetylcholinergic system, endothelium-dependent coronary vasodilation, pressure-dependent autoregulation, and, most importantly, metabolic demand. These increases in blood pressure and coronary arterial vasoconstriction are usually mild and insignificant, but rarely may be profound, with potential for deleterious outcome to the experimental subject or patient. In this chapter, we review the known and theoretical pathophysiology behind UAS.

Original languageEnglish (US)
Title of host publicationBeta-Blockers
Subtitle of host publicationPhysiological, Pharmacological and Therapeutic Implications
PublisherNova Science Publishers, Inc.
Number of pages63
ISBN (Electronic)9781536133127
ISBN (Print)9781536133110
StatePublished - Jan 1 2018

ASJC Scopus subject areas

  • Medicine(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)


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