Neuronal, glial and synaptic remodeling in the adult hypothalamus: functional consequences and role of cell surface and extracellular matrix adhesion molecules.
Neurochemistry International. 2004-09-01; 45(4): 491-501
DOI: 10.1016/j.neuint.2003.11.003
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1. Neurochem Int. 2004 Sep;45(4):491-501.
Neuronal, glial and synaptic remodeling in the adult hypothalamus: functional
consequences and role of cell surface and extracellular matrix adhesion
molecules.
Theodosis DT(1), Piet R, Poulain DA, Oliet SH.
Author information:
(1)INSERM U378 Neurobiologie Morphofonctionelle, Univeristé Victor Segalen, 1 Rue
Camille Saint-Saëns, F33077 Bordeaux Cedex, France.
The adult hypothalamo-neurohypophysial system (HNS) undergoes activity-dependent
morphological plasticity which modifies astrocytic coverage of its oxytocinergic
neurons and their synaptic inputs. Thus, during physiological conditions that
enhance central and peripheral release of oxytocin (OT), adjacent somata and
dendrites of OT neurons become extensively juxtaposed, without intervening
astrocytic processes and receive an increased number of synapses. The
morphological changes occur within a few hours and are reversible with
termination of stimulation. The reduced astrocytic coverage has direct functional
consequences since it modifies extracellular ionic homeostasis, synaptic
transmission, and the size and geometry of the extracellular space. It also
contributes indirectly to neuronal function by permitting formation of synapses
on neuronal surfaces freed of astrocytic processes. Overall, such remodeling is
expected to potentiate activated neuronal firing, especially in clusters of
tightly packed neurons, an anatomical arrangement characterizing OT neurons. This
plasticity connotes dynamic cell interactions that must bring into play cell
surface and extracellular matrix adhesive proteins like those intervening in
developing neuronal systems undergoing neuronal-glial and synaptogenic
transformations. It is worth noting, therefore, that adult HNS neurons and glia
continue to express such molecules, including polysialic acid (PSA)-enriched
neural cell adhesion molecule (PSA-NCAM) and the glycoprotein, tenascin-C. PSA is
a large, complex sugar on the extracellular domain of NCAM considered a negative
regulator of adhesion; it occurs in large amounts on the surfaces of HNS neurons
and astrocytes. Tenascin-C, on the other hand, possesses adhesive and repulsive
properties; it is secreted by HNS astrocytes and occurs in extracellular spaces
and on cell surfaces after interaction with appropriate ligands. These molecules
have been considered permissive factors for morphological plasticity. However,
because of their localization and inherent properties, they may also serve to
modulate the extracellular environment and in consequence, synaptic and volume
transmission in a system in which the extracellular compartment is constantly
being modified.
Copyright 2003 Elsevier Ltd.
DOI: 10.1016/j.neuint.2003.11.003
PMID: 15186915 [Indexed for MEDLINE]