Autonomic control of cerebral blood flow: fundamental comparisons between peripheral and cerebrovascular circulations in humans. (10th December 2021)

• Record Type: Journal Article
• Authors: Koep, Jodie L.; Taylor, Chloe E.; Coombes, Jeff S.; Bond, Bert; Ainslie, Philip N.; Bailey, Tom G.
• Is Part Of: Journal of physiology. Volume 600:Number 1(2022)
• Page Start: 15
• Page End: 39
• Publication Date: 2021-12-10
• Subjects: adrenergic receptors -- cerebrovascular regulation -- neural control -- parasympathetic nerve activity -- sympathetic nerve activity; Physiology -- Periodicals; 612.005
• DOI: 10.1113/JP281058
• Languages: English
• ISSNs: 0022-3751

Abstract

Abstract: Understanding the contribution of the autonomic nervous system to cerebral blood flow (CBF) control is challenging, and interpretations are unclear. The identification of calcium channels and adrenoreceptors within cerebral vessels has led to common misconceptions that the function of these receptors and actions mirror those of the peripheral vasculature. This review outlines the fundamental differences and complex actions of cerebral autonomic activation compared with the peripheral circulation. Anatomical differences, including the closed nature of the cerebrovasculature, and differential adrenoreceptor subtypes, density, distribution and sensitivity, provide evidence that measures on peripheral sympathetic nerve activity cannot be extrapolated to the cerebrovasculature. Cerebral sympathetic nerve activity seems to act opposingly to the peripheral circulation, mediated at least in part by changes in intracranial pressure and cerebral blood volume. Additionally, heterogeneity in cerebral adrenoreceptor distribution highlights region‐specific autonomic regulation of CBF. Compensatory chemo‐ and autoregulatory responses throughout the cerebral circulation, and interactions with parasympathetic nerve activity are unique features to the cerebral circulation. This crosstalk between sympathetic and parasympathetic reflexes acts to ensure adequate perfusion of CBF to rising and falling perfusion pressures, optimizing delivery of oxygen and nutrients to the brain, while attempting to maintain blood volume and intracranial pressure. Herein, we highlight the distinct similarities and differences between autonomic control of cerebral and peripheral blood flow, and the regional specificity of sympathetic and parasympathetic regulation within the cerebrovasculature. Future research directions are outlined with the goal to further our understanding of autonomic control of CBF in humans. Abstract : Abstract figure legend : Summary of the differential regulatory pathways underpinning peripheral and cerebral blood flow. This illustrates how the actions of elevations in sympathetic activation on the cerebrovascular circulation depend upon the region and receptor being acted upon, as well as interactions with cholinergic receptors. Additionally, cerebral sympathetic activity may be directly mediated by cerebral blood volume and intracranial pressure, in order to maintain these within limits or regulation. A better understanding of how this regional heterogeneity translates to physiological functioning is required. However, it is apparent that peripheral sympathetic nerve activity evidence for control of blood flow cannot be extrapolated to the cerebrovasculature.