Ultrastructural Findings in Human Spinal Pia Mater in Relation to Subarachnoid Anesthesia

Reina, Miguel Ángel; Casasola, Oscar de León; Villanueva, M C; López, Andrés; Machés, Fabiola; Andrés, José Antonio De

doi:10.1213/01.ane.0000113240.09354.e9

Cited by 65 publications

(36 citation statements)

References 10 publications

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“…Potential routes of entry from the CSF into the PVS include specialized pores, termed stomata, recently demonstrated on the adventitial lining cells of leptomeningeal vessels in the SAS of the rat by scanning electron microscopy [137] (Fig. 1b), confirming earlier decades-old identification of such structures in cats [199]; similar pores may also exist on the pia [30,146], providing an additional route into the PVS via the subpial space (discussed in [137]). It has become increasingly clear that substances within the CSF may potentially access and distribute along the PVS to varying extents all throughout the cerebrovascular tree, e.g., large full length antibodies (immunoglobulin G) have been shown to access the PVS of arterioles (Fig.…”

Section: Blood Vessels and The Perivascular Spacesupporting

confidence: 74%

The role of brain barriers in fluid movement in the CNS: is there a ‘glymphatic’ system?

et al. 2018

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Brain fluids are rigidly regulated to provide stable environments for neuronal function, e.g., low K + , Ca 2+ , and protein to optimise signalling and minimise neurotoxicity. At the same time, neuronal and astroglial waste must be promptly removed. The interstitial fluid (ISF) of the brain tissue and the cerebrospinal fluid (CSF) bathing the CNS are integral to this homeostasis and the idea of a glia-lymph or 'glymphatic' system for waste clearance from brain has developed over the last 5 years. This links bulk (convective) flow of CSF into brain along the outside of penetrating arteries, glia-mediated convective transport of fluid and solutes through the brain extracellular space (ECS) involving the aquaporin-4 (AQP4) water channel, and finally delivery of fluid to venules for clearance along peri-venous spaces. However, recent evidence favours important amendments to the 'glymphatic' hypothesis, particularly concerning the role of glia and transfer of solutes within the ECS. This review discusses studies which question the role of AQP4 in ISF flow and the lack of evidence for its ability to transport solutes; summarizes attributes of brain ECS that strongly favour the diffusion of small and large molecules without ISF flow; discusses work on hydraulic conductivity and the nature of the extracellular matrix which may impede fluid movement; and reconsiders the roles of the perivascular space (PVS) in CSF-ISF exchange and drainage. We also consider the extent to which CSF-ISF exchange is possible and desirable, the impact of neuropathology on fluid drainage, and why using CSF as a proxy measure of brain components or drug delivery is problematic. We propose that new work and key historical studies both support the concept of a perivascular fluid system, whereby CSF enters the brain via PVS convective flow or dispersion along larger caliber arteries/arterioles, diffusion predominantly regulates CSF/ISF exchange at the level of the neurovascular unit associated with CNS microvessels, and, finally, a mixture of CSF/ISF/waste products is normally cleared along the PVS of venules/veins as well as other pathways; such a system may or may not constitute a true 'circulation', but, at the least, suggests a comprehensive re-evaluation of the previously proposed 'glymphatic' concepts in favour of a new system better taking into account basic cerebrovascular physiology and fluid transport considerations.

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Section: Blood Vessels and The Perivascular Spacesupporting

confidence: 74%

The role of brain barriers in fluid movement in the CNS: is there a ‘glymphatic’ system?

et al. 2018

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“…This thickening of the membranes may be somewhat counteracted by the appearance of fenestrations in the adult rat pia (Morse and Low 1972), which may facilitate 5-HT entrance into the spinal cord. Fenestrations are also observed in human lumbar pia mater (Reina et al 2004).…”

Section: Implication Of the Findingsmentioning

confidence: 82%

Serotonin Concentrations in the Lumbosacral Spinal Cord of the Adult Rat Following Microinjection or Dorsal Surface Application

Brumley

Hentall

Pinzón

et al. 2007

Journal of Neurophysiology

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Brumley MR, Hentall ID, Pinzon A, Kadam BH, Blythe A, Sanchez FJ, Taberner AM, Noga BR. Serotonin concentrations in the lumbosacral spinal cord of the adult rat following microinjection or dorsal surface application. J Neurophysiol 98: 1440 -1450, 2007. First published July 18, 2007 doi:10.1152/jn.00309.2007. Application of neuroactive substances, including monoamines, is common in studies examining the spinal mechanisms of sensation and behavior. However, affected regions and time courses of transmitter activity are uncertain. We measured the spatial and temporal distribution of serotonin [5-hydroxytryptamine (5-HT)] in the lumbosacral spinal cord of halothane-anesthetized adult rats, following its intraspinal microinjection or surface application. Carbon fiber microelectrodes (CFMEs) were positioned at various locations in the spinal cord and oxidation currents corresponding to extracellular 5-HT were measured by fast cyclic voltammetry. Intraspinal microinjection of 5-HT (100 M, 1-3 l) produced responses that were most pronounced at CFMEs positioned Յ800 m from the drug micropipette: 5-HT concentration was significantly higher (1.43 vs. Ͻ0.28% of initial concentration) and response latency was shorter (67.1 vs. 598.2 s) compared with more distantly positioned CFMEs. Treatment with the selective 5-HT reuptake inhibitor clomipramine only slightly affected the spread of microinjected 5-HT. Surface application over several segments led to a transient rise in concentration that was usually apparent within 30 s and was dramatically attenuated with increasing depth: 0.25% of initial concentration (1 mM) within 400 m of the dorsal surface and Ͻ0.001% between 1,170 and 2,000 m. This initial response to superfusion was sometimes followed by a gradual increase to a new concentration plateau. In sum, compared with bath application, microinjection can deliver about tenfold higher transmitter concentrations, but to much more restricted areas of the spinal cord.

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“…The inner part of the nerve root cuff has a thin layer with transition cells originating from the arachnoid, trabecular arachnoids, and pia mater. 5,6 This transition tissue is in close contact with the axons located in the outer layer of the motor and sensory cords and is the barrier that controls the passage of substances from the epidural space 5 (Figs. 1B, C).…”

Section: Discussionmentioning

confidence: 99%

Morphologic Study of Nerve Root and Types of Needle Used in Transforaminal Injections

Hernández-García

Reina²,

Prats-Galino

et al. 2011

Regional Anesthesia and Pain Medicine

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Ultrastructural Findings in Human Spinal Pia Mater in Relation to Subarachnoid Anesthesia

Cited by 65 publications

References 10 publications

The role of brain barriers in fluid movement in the CNS: is there a ‘glymphatic’ system?

The role of brain barriers in fluid movement in the CNS: is there a ‘glymphatic’ system?

Serotonin Concentrations in the Lumbosacral Spinal Cord of the Adult Rat Following Microinjection or Dorsal Surface Application

Morphologic Study of Nerve Root and Types of Needle Used in Transforaminal Injections

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