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J Cereb Blood Flow Metab. 2015 Mar;35(3):521-6. doi: 10.1038/jcbfm.2014.229. Epub 2014 Dec 17.

Evaluation of cerebrovascular impedance and wave reflection in mouse by ultrasound.

Author information

1
1] Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada [2] Division of Physiology and Experimental Medicine, Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada.
2
Division of Physiology and Experimental Medicine, Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada.
3
Mouse Imaging Centre, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada.
4
1] Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada [2] Mouse Imaging Centre, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, Toronto, Ontario, Canada.

Abstract

Genetic and surgical mouse models are commonly used to study cerebrovascular disease, but their size makes invasive hemodynamic testing technically challenging. The purpose of this study was to demonstrate a noninvasive measurement of cerebrovascular impedance and wave reflection in mice using high-frequency ultrasound in the left common carotid artery (LCCA), and to examine whether microvascular changes associated with hypercapnia could be detected with such an approach. Ten mice (C57BL/6J) were studied using a high-frequency ultrasound system (40 MHz). Lumen area and blood flow waveforms were obtained from the LCCA and used to calculate pulse-wave velocity, input impedance, and reflection amplitude and transit time under both normocapnic and hypercapnic (5% CO2) ventilation. With hypercapnia, vascular resistance was observed to decrease by 87%±12%. Although the modulus of input impedance was unchanged with hypercapnia, a phase decrease indicative of increased total arterial compliance was observed at low harmonics together with an increased reflection coefficient in both the time (0.57±0.08 versus 0.68±0.08, P=0.04) and frequency domains (0.62±0.08 versus 0.73±0.06, P=0.02). Interestingly, the majority of LCCA blood flow was found to pass into the internal carotid artery (range=76% to 90%, N=3), suggesting that hemodynamic measurements in this vessel are a good metric for intracerebral reactivity in mouse.

PMID:
25515209
PMCID:
PMC4348395
DOI:
10.1038/jcbfm.2014.229
[Indexed for MEDLINE]
Free PMC Article
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