Functional Coupling between Neurons and Glia
Veronica
Alvarez-Maubecin1,
Fernando
García-Hernández2,
John T.
Williams1, and
Elisabeth J.
Van
Bockstaele2
1 Vollum Institute for Advanced Biomedical Research,
Oregon Health Science University, Portland, Oregon 97201, and
2 Department of Pathology, Anatomy, and Cell Biology,
Thomas Jefferson University, Philadelphia, Pennsylvania 19107
Neuronal-glial interactions play an important role in information
processing in the CNS. Previous studies have indicated that electrotonic coupling between locus ceruleus (LC) neurons is
involved in synchronizing the spontaneous activity. The results of the present study extend the functional electrotonic coupling to
interactions between neurons and glia. Spontaneous oscillations in the
membrane potential were observed in a subset of glia. These
oscillations were synchronous with the firing of neurons, insensitive
to transmitter receptor antagonists and disrupted by carbenoxolone, a
gap junction blocker. Hyperpolarization of neurons with [Met]
5enkephalin blocked the oscillations in glia.
Selective depolarization of glia with a glutamate transporter substrate
(L-
-aminoadipic acid) increased the neuronal firing
rate, suggesting that changes in the membrane potential of glia can
modulate neuronal excitability through heterocellular coupling.
Dye-coupling experiments further confirmed that small molecules could
be transferred through gap junctions between these distinct cell types.
No dye transfer was observed between neurons and oligodendrocytes or
between astrocytes and oligodendrocytes, suggesting that the junctional
communication was specific for astrocytes and neurons. Finally,
immunoelectron microscopy studies established that connexins, the
proteins that form gap junctions, were present on portions of the
plasmalemma, bridging the cytoplasm of neurons and glia in LC. This
heterocellular coupling extends the mechanisms by which glia
participate in the network properties of the LC in which the degree of
coupling is thought to influence cognitive performance.
Key words:
electrotonic coupling; gap junction; neuronal-glial
interactions; membrane potential oscillations; noradrenergic neurons; connexins
Copyright © 2000 Society for Neuroscience 0270-6474/00/20114091-08$05.00/0