The Journal of Neuroscience, December 15, 2002, 22(24):10720-10730
Bergmann Glia GABAA Receptors Concentrate on the
Glial Processes That Wrap Inhibitory Synapses
Raquel
Riquelme,
Celia P.
Miralles, and
Angel L.
De Blas
Department of Physiology and Neurobiology, University of
Connecticut, Storrs, Connecticut 06269
We studied the cellular and subcellular distribution of
GABAA receptors in the Bergmann glia and Purkinje cells in
the molecular layer of the cerebellum by using electron microscopy
postembedding immunogold techniques. Gold particles corresponding to
2 and
1 immunoreactivity were localized in Bergmann glia
processes that wrapped Purkinje cell somata, dendritic shafts, and some dendritic spines. The gold particles were mainly located on the glial
plasma membrane or intracellularly but near the plasma membrane. The
density of gold particles corresponding to
2 and
1
GABAA receptor subunits was 4.3-fold higher in the glial
processes wrapping Purkinje cell somata than in the glial processes
wrapping Purkinje cell dendritic spines. Moreover, the Bergmann glia
GABAA receptors were often located in close proximity to
the type II GABAergic synapses made by the basket cell axons on
Purkinje cell somata. These GABAergic synapses were enriched in
neuronal GABAA receptors containing
1 and
2/3
subunits. Unexpectedly, 2.8% of the Purkinje cell dendritic spines
also showed immunoreactivity for the neuronal
1 or
2/3 subunits,
which were located on the spine in type I synapses or
extrasynaptically. Double-labeling immunogold experiments showed that
~50% of the dendritic spines that were immunolabeled with the
neuronal GABAA receptors were wrapped by Bergmann glia processes containing glial GABAA receptors. These results
are consistent with a role of the Bergmann glial GABAA
receptors in sensing GABAergic synaptic function.
Key words:
GABAA receptor; Bergmann glia; astrocyte; synapse; Purkinje cell; neuron; glia; immunogold; electron microscopy; immunocytochemistry; cerebellum
Copyright © 2002 Society for Neuroscience 0270-6474/02/222410720-11$05.00/0