Perivascular space

McCandless EE, Wang Q, Woerner BM, Harper JM, Klein RS (2006) CXCL12 Umits inflammation by localizing mononuclear infiltrates to the perivascular space during experimental autoimmune encephalomyelitis. J Immunol 177 8053-8064 McCandless EE, Piccio L, Woerner BM, Schmidt RE, Rubin JB, Cross AH, Klein RS (2008a) Pathologic expression of CXCL12 at the blood brain barrier correlates with severity of multiple sclerosis. Am J Pathol... 

The brain lacks connection with the lymphatic system. The interstitial fluid drains into the perivascular space, which surrounds arteries and veins, and from there into the sub-arachnoid space where it mixes with the cerebrospinal fluid. This is secreted by the choroid plexuses, which are capillary-rich outgrowths into cavities within the brain, known as ventricles. From the ventricles, cerebrospinal fluid flows through channels to the surface of the brain and... 

VR space, or perivascular space, is an invagination of the subpial space surrounding a vessel going into the brain. VR spaces surround arteries, veins, arterioles, and venules. VR spaces enlarge and become numerous by advancing age, hypertension,... 

Histopathological features of white matter lesions include diffuse myelin pallor (sparing the U-fibers, that are supplied by cortical branches), astrocytic gliosis, widening of perivascular spaces, and loss of oligodendrocytes leading to rarefaction, spongiosis, as well as loss of myelin and axons without definite necrosis, which has also been described as incomplete white matter infarction, which may finally... 

Passive reabsorption of lipid-soluble, un-lonized drug which has been concentrated so that the Intraluminal concentration is greater than that in the perivascular space. 

Cardiovascular In rodents, lymphohistiocytic infiltrates have been observed in the heart and in the perivascular space in various organs. Tissue macrophages in the heart can contain basophilic granules. In monkeys, no changes in ECG, heart rate, or blood pressure have been observed with numerous oligonucleotides. Under conditions when complement is activated, changes in blood pressure and cardiovascular collapse due to hypotension have been observed [55], but we have shown this to be related to complement activation rather than a direct effect on the cardiovascular system. (Of course, other mechanisms for hypotension could occur with other chemistries. For example, if an oligonucleotide formulation or its metabolic products chelates calcium, reductions in ionizable calcium could also produce a hypotensive crisis.) For most PS ODNs the most likely cause of hypotension is complement activation as demonstrated with complement inhibitors. 

The vessel wall changes found more frequently and more distinctly in the animals subjected to ECT consist of characteristic sac-like dilatations of the perivascular spaces, which in some cases contain histiocytic elements. The glial reaction, of the progressive type, consists of an increase in the number of the small glial elements in the parenchyma and satellitosis beside the nerve cells. The nerve cell changes observed are in the form of various stages of chromophobia, frequently with coincident nuclear hyperchromatism. The arrangement of such cells is mainly focal. 

For the second route, leukocytes reach the CNS from blood to subarachnoid space. In this pathway, leukocytes travel from the internal carotid artery, across postcapillary venules at the pial surface of the brain into the subarachnoid space and the Virchow-Robin perivascular spaces. There, they might encounter cells of the monocyte/myeloid lineage that are competent for antigen presentation. The perivascular regions, wkere there is direct communication with the CSF compartment, are considered probable sites of lymphocyte-APC interaction and therefore, of immune surveillance of CNS. This pathway is also dependent on P-selecdn. 

Astrocytes are responsible in maintaining extracellular ion concentration at a level compatible with neuronal function. Astrocytes form a syncytium through which it efficiently redistributes from perineuronal to perivascular space. Such redistribution of is mediated by inwardly rectifying ion channels. One such ion channel Kir 4.1 is expressed in astrocytes surrounding neuronal synapses as well as blood vessels in the brain (Nagelhus et al., 2004). 

Persistence of T cells in the brain is a rare event and is associated wdth chronic pathology forming tertiary lymphoid structure that provides support and activation signals by DCs and macrophages. These structures are present in perivascular spaces, meninges and choroid plexus, and w ere studied mostly in multiple sclerosis (see Chapter 18). 

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