Abstract

BackgroundFluid homeostasis in the central nervous system (CNS) is essential for normal neurological function. Cerebrospinal fluid (CSF) in the subarachnoid space and interstitial fluid circulation in the CNS parenchyma clears metabolites and neurotransmitters and removes pathogens and excess proteins. A thorough understanding of the normal physiology is required in order to understand CNS fluid disorders, including post-traumatic syringomyelia. The aim of this project was to compare fluid transport, using quantitative imaging of tracers, in the spinal cord from animals with normal and obstructed spinal subarachnoid spaces.MethodsA modified extradural constriction model was used to obstruct CSF flow in the subarachnoid space at the cervicothoracic junction (C7–T1) in Sprague–Dawley rats. Alexa-Fluor 647 Ovalbumin conjugate was injected into the cisterna magna at either 1 or 6 weeks post–surgery. Macroscopic and microscopic fluorescent imaging were performed in animals sacrificed at 10 or 20 min post–injection. Tracer fluorescence intensity was compared at cervical and thoracic spinal cord levels between control and constriction animals at each post-surgery and post-injection time point. The distribution of tracer around arterioles, venules and capillaries was also compared.ResultsMacroscopically, the fluorescence intensity of CSF tracer was significantly greater in spinal cords from animals with a constricted subarachnoid space compared to controls, except at 1 week post-surgery and 10 min post-injection. CSF tracer fluorescence intensity from microscopic images was significantly higher in the white matter of constriction animals 1 week post surgery and 10 min post-injection. At 6 weeks post–constriction surgery, fluorescence intensity in both gray and white matter was significantly increased in animals sacrificed 10 min post-injection. At 20 min post-injection this difference was significant only in the white matter and was less prominent. CSF tracer was found predominantly in the perivascular spaces of arterioles and venules, as well as the basement membrane of capillaries, highlighting the importance of perivascular pathways in the transport of fluid and solutes in the spinal cord.ConclusionsThe presence of a subarachnoid space obstruction may lead to an increase in fluid flow within the spinal cord tissue, presenting as increased flow in the perivascular spaces of arterioles and venules, and the basement membranes of capillaries. Increased fluid retention in the spinal cord in the presence of an obstructed subarachnoid space may be a critical step in the development of post-traumatic syringomyelia.

Highlights

  • Fluid homeostasis in the central nervous system (CNS) is essential for normal neurological function

  • Macroscopic imaging—Cerebrospinal fluid (CSF) tracer distribution along the neuraxis Detectable differences in the distribution and fluorescence intensity of CSF tracer were observed in spinal cords of animals from different treatment groups, at both 1 and 6 weeks after the initial surgery (Fig. 2)

  • In control animals 10 min after tracer injection, the highest intensity of CSF tracer was observed in the brain and intensity decreased gradually in the caudal direction

Read more

Summary

Introduction

Fluid homeostasis in the central nervous system (CNS) is essential for normal neurological function. Cerebrospinal fluid (CSF) is a clear, colorless fluid that bathes the central nervous system (CNS) It has several critical functions, including maintenance of a homeostatic environment for neurons and glia, transport of neuroactive substances around the CNS, and acting as a drainage system for CNS interstitial fluid [1,2,3,4,5,6]. Efflux of subarachnoid CSF may occur via cranial and spinal nerves [9] In addition to this ‘macrocirculation’, there is an interchange of CSF and interstitial fluid (ISF), allowing for a ‘microcirculation’ of ISF through the CNS parenchyma. This route of fluid flow potentially brings neuroactive substances into contact with neuronal cells and facilitates the removal of waste products. The details of this interchange are still poorly understood [5, 6, 10]

Objectives
Methods
Results
Discussion
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call