Journal of Neuroscience, Vol 13, 4412-4421, Copyright © 1993 by Society for Neuroscience
Membrane properties of ameboid microglial cells in the corpus callosum slice from early postnatal mice
J Brockhaus, S Ilschner, RB Banati and H Kettenmann
Department of Neurobiology, University of Heidelberg, Germany.
Microglial cells in culture are distinct from neurons, macroglial cells,
and macrophages of tissues other than brain with respect to their membrane
current pattern. To assess these cells in the intact tissue, we have
applied the patch-clamp technique to study membrane currents in microglial
cells from acute, whole brain slices of 6-9-d- old mice in an area of
microglial cell invasion, the cingulum. As strategies to identify
microglial cells prior to or after recording, we used binding and
incorporation of Dil-acetylated low-density lipoproteins, binding of
fluorescein isothiocyanate-coupled IgG via microglial Fc-receptors, and
ultrastructural characterization. As observed previously for cultured
microglial cells, depolarizing voltage steps activate only minute if any
membrane currents, while hyperpolarizing voltage steps induced large inward
currents. These currents exhibited properties of the inwardly rectifying K+
channel in that the reversal potential depended on the transmembrane K+
gradient, inactivation time constants decreased with hyperpolarization, and
the current was blocked by tetraethylammonium (50 mM). This study
represents the first attempt to assess microglial cells in situ using
electrophysiological methods. It opens the possibility to address questions
related to the function of microglial cells in the intact CNS.
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