Polysialic acid is required for active phases of morphological plasticity of neurosecretory axons and their glia.
The morphology of axons and astrocytes in the neurohypophysis changes considerably during physiological stimulation, increasing neurovascular contact and facilitating neurosecretion. We here assessed the contribution of alpha2, 8-linked polysialic acid (PSA), which intervenes in axonal changes during development and covers all neurohypophysial axon and glial surfaces. Using an in vitro model, we first analyzed neurohypophysial ultrastructure under different conditions of plasticity. After 2 h incubation in hyperosmotic medium or with the beta-adrenergic agonist, isoprenaline, neurovascular contact significantly increased, due essentially to an enhanced number of terminals, and gliovascular contact decreased correspondingly. This morphology was maintained during 22 h exposure to isoprenaline and reversed 2 h after agonist washout. Removal of PSA from cell surfaces with endoneurominidase prevented stimulation-related induction and reversal of axon and glial changes but had no effect once remodeling had occurred. PSA, therefore, by promoting dynamic cell interactions, is necessary for plasticity of axons and their associated glia.
Monlezun
Stéphanie
S
Laboratory of Morphofunctional Neurobiology Inserm U378; University Victor Segalen-Bordeaux II, F33077 Bordeaux, France.
Ouali
Saliha
S
Poulain
Dominique A
DA
Theodosis
Dionysia T
DT
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000502:physiology / Q000648:ultrastructure; D006026:Glycoside Hydrolases / Q000494:pharmacology; D006982:Hypertonic Solutions / Q000494:pharmacology; D007365:Intercellular Junctions / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D008297:Male; D046529:Microscopy, Electron, Transmission; D009457:Neuroglia / Q000378:metabolism* / Q000648:ultrastructure; D009473:Neuronal Plasticity / Q000502:physiology*; D009924:Organ Culture Techniques; D010904:Pituitary Gland, Posterior / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D012794:Sialic Acids / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology
D000318:Adrenergic beta-Agonists; D006982:Hypertonic Solutions; D012794:Sialic Acids; C021319:polysialic acid; D006026:Glycoside Hydrolases; C090534:endo-alpha-sialidase