The Journal of Neuroscience, May 15, 1999, 19(10):3836-3846
Muscarinic Control of Cytoskeleton in Perisynaptic Glia
John
Georgiou1,
Richard
Robitaille2, and
Milton P.
Charlton1
1 Department of Physiology, Medical Research Council
Group in Nerve Cells and Synapses, and Neuroscience Network, University
of Toronto, Toronto, Ontario, Canada M5S 1A8, and 2 Centre
de Recherche en Sciences Neurologiques, and Département de
Physiologie, Université de Montréal, Montréal,
Québec, Canada H3C 3J7
Similar to astrocytes at CNS synapses, perisynaptic Schwann cells
(PSCs) surround nerve terminals at the neuromuscular junction (NMJ).
These special teloglial cells are sensitive to neurotransmitters and
upregulate glial fibrillary acidic protein (GFAP) when deprived of
synaptic activity. We found that activation of muscarinic acetylcholine receptors (mAChRs) at PSCs, but not purinergic (ATP and adenosine) or
peptidergic [substance P (SP) and calcitonin gene-related peptide (CGRP)] receptors, prevented this upregulation. When applied onto single PSCs, muscarine evoked Ca2+ responses that
fatigued but prevented upregulation of this glial cytoskeletal protein.
Application of ATP onto single PSCs evoked Ca2+
signals that showed little fatigue, and GFAP upregulation occurred. Thus, Ca2+ signals alone cannot prevent GFAP
upregulation in the PSCs. After blockade of cholinergic receptors by
gallamine, neuronal activity was not effective in maintaining low GFAP
levels in the perisynaptic glia. Last, immunohistochemistry disclosed
mAChRs on PSCs and nearby fibroblasts. Thus, acetylcholine secreted by
the nerve terminal acts on the PSCs via mAChRs to regulate GFAP.
Cytoskeletal changes may influence perisynaptic glial functions,
including growth, remodeling, and modulation of the synapse.
Key words:
nerve-glia signaling; nerve terminal; glial cell; transmitter; synapse; neuromuscular junction; terminal Schwann cell; GFAP; muscarine; muscarinic acetylcholine receptors; Ca2+; cytoskeleton; plasticity
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