Changes in intrathoracic pressure, not arterial pulsations, exert the greatest effect on tracer influx in the spinal cord

Fluids and Barriers of the CNS

Simon McMullan¹  Marcus A. Stoodley²  Sarah J. Hemley²  Shinuo Liu²  Lynne E. Bilston³  Robert Lloyd³  Neftali Flores Rodriguez⁴  Courtney Wright⁴ 

[1] Department of Biological Sciences, Faculty of Medicine, Health and Human Sciences, Macquarie University, 2109, Macquarie Park, NSW, Australia;Department of Clinical Medicine, Faculty of Medicine, Health and Human Sciences, Macquarie University, 2109, Macquarie Park, NSW, Australia;Neuroscience Research Australia, Prince of Wales Clinical School, University of New South Wales, 2031, Sydney, NSW, Australia;Sydney Microscopy and Microanalysis, Brain and Mind Centre, The University of Sydney, 2006, Camperdown, NSW, Australia;

关键词: Cerebrospinal fluid;    Spinal cord;    Intrathoracic pressure;    Hypertension;    Tachycardia;    Respiration;   

DOI  :  10.1186/s12987-022-00310-6

来源: Springer

【 摘 要 】

BackgroundCerebrospinal fluid (CSF) circulation in the brain has garnered considerable attention in recent times. In contrast, there have been fewer studies focused on the spine, despite the expected importance of CSF circulation in disorders specific to the spine, including syringomyelia. The driving forces that regulate spinal CSF flow are not well defined and are likely to be different to the brain given the anatomical differences and proximity to the heart and lungs. The aims of this study were to determine the effects of heart rate, blood pressure and respiration on the distribution of CSF tracers in the spinal subarachnoid space, as well as into the spinal cord interstitium.MethodsIn Sprague Dawley rats, physiological parameters were manipulated such that the effects of spontaneous breathing (generating alternating positive and negative intrathoracic pressures), mechanical ventilation (positive intrathoracic pressure only), tachy/bradycardia, as well as hyper/hypotension were separately studied. To investigate spinal CSF hydrodynamics, in vivo near-infrared imaging of intracisternally infused indocyanine green was performed. CSF tracer transport was further characterised with in vivo two-photon intravital imaging. Tracer influx at a microscopic level was quantitatively characterised by ex vivo epifluorescence imaging of fluorescent ovalbumin.ResultsCompared to mechanically ventilated controls, spontaneous breathing animals had significantly greater movement of tracer in the subarachnoid space. There was also greater influx into the spinal cord interstitium. Hypertension and tachycardia had no significant effect on spinal subarachnoid spinal CSF tracer flux and exerted less effect than respiration on tracer influx into the spinal cord.ConclusionsIntrathoracic pressure changes that occur over the respiratory cycle, particularly decreased intrathoracic pressures generated during inspiration, have a profound effect on tracer movement after injection into spinal CSF and increase cord parenchymal tracer influx. Arterial pulsations likely drive fluid transport from perivascular spaces into the surrounding interstitium, but their overall impact is less than that of the respiratory cycle on net tracer influx.

【 授权许可】

CC BY