title: Modeling the role of osmotic forces in the cerebrovascular response to CO2.
abstract: Increases in blood osmolarity have been shown to exert a vasodilatory effect on cerebral and other vasculature, with accompanying increases in blood flow. It has also been shown that, through an influence on blood concentration of the bicarbonate ion and pH, changes in blood levels of CO2 can alter blood osmolarity sufficiently to have an impact on vessel diameter. We propose here that this phenomenon plays a previously unappreciated role in CO2-mediated vasodilation, and present a biophysical model of osmotically driven vasodilation. Our model, which is based on literature data describing CO2-dependent changes in blood osmolarity and hydraulic conductivity (Lp) of the blood-brain barrier, is used to predict the change in cerebral blood flow (CBF) associated with osmotic forces arising from a specific hypercapnic challenge. Modeled changes were then compared with actual CBF changes determined using arterial spin-labeling (ASL) MRI. For changes in the arterial partial pressure of CO2 (PaCO2) of 20 mmHg, our model predicted increases of 80% from baseline CBF with a temporal evolution that was comparable to the measured hemodynamic responses. Our modeling results suggest that osmotic forces could play a significant role in the cerebrovascular response to CO2.
authors: Institut de génie biomédical, Département de physiologie, Université de Montréal, Montreal, QC, Canada; Unité de neuroimagerie fonctionnelle, Centre de recherche de l'institut universitaire de gériatrie de Montréal, Montreal, QC, Canada. Electronic address: felipe.tancredi@umontreal.ca.
authors: F B
authors: FB
authors: Tancredi
authors: Unité de neuroimagerie fonctionnelle, Centre de recherche de l'institut universitaire de gériatrie de Montréal, Montreal, QC, Canada; Département de pharmacologie, Faculté de médicine, Université de Montréal, Montréal, QC, Canada; Neuroscience Research Group, Faculté de médicine, Université de Montréal, Montréal, QC, Canada.
authors: H
authors: H
authors: Girouard
authors: Institut de génie biomédical, Département de physiologie, Université de Montréal, Montreal, QC, Canada; Unité de neuroimagerie fonctionnelle, Centre de recherche de l'institut universitaire de gériatrie de Montréal, Montreal, QC, Canada.
authors: R D
authors: RD
authors: Hoge
mesh_terms: D002245:Carbon Dioxide / Q000008:administration & dosage*; D002560:Cerebrovascular Circulation; D006801:Humans; D008954:Models, Biological; D009995:Osmosis
chemical_list: D002245:Carbon Dioxide