[Abstract Title]. - Society for Neuroscience

potential therapeutic benefits of 17β-estradiol not only in treating CNS injury but other
conditions in which a loss of K + and glutamate homeostasis.
Disclosures: M.L. Olsen , None; C.L. Floyd, None; H. Sontheimer, None.
Poster
234. A-Type Potassium Channels
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 234.20/C44
Topic: B.04.c. Potassium channels: Physiology
Support: NIH Grant EY12949
Title: Differential Kir4.1 channel expression in complex and passive astrocytes revealed by
mouse transgenesis
Authors: X. TANG, K. TANIGUCHI, *P. KOFUJI;
Dept Neurosci, Univ. Minnesota, Minneapolis, MN
Abstract: Results from several laboratories have indicated that the inwardly rectifying
potassium channel Kir4.1 underlies the principal potassium conductance in astrocytes and retinal
Müller cells and have presented evidences of its critical role in extracellular potassium buffering
in the retina and brain. We have explored a genetic approach to provide high resolution cellular
mapping of Kir4.1 expression by employing bacterial artificial chromosome (BAC) transgenic
mice that express Enhanced Green Fluorescent Protein (EGFP) under the transcriptional control
of the Kir4.1 gene. Analysis performed in brain sections of Kir4.1-EGFP transgenic mice
showed that transgenic expression of EGFP was well correlated with Kir4.1 and was prominent
in GFAP-expressing astrocytes. In addition, weak expression of EGFP was detected in NG2expressing
glial cells. Whole cell voltage clamp recordings in hippocampus indicate that these
two glial cell types defined by the EGFP levels of expression display the properties of the so
called passive and complex astrocytes. The strongly fluorescent EGFP glial cells have linear
current-voltage relationships and are strongly coupled via gap junctions. The weakly fluorescent
EGFP glial cells display non-linear current voltage-relationships and are not electrically coupled
extensively with other cells. Pharmacological blockade of Kir4.1 channels with desipramine or
cesium indicate that Kir4.1 channels constitute the dominant resting potassium conductance in
complex astrocytes but not in passive astrocytes. These results suggest differential roles of
Kir4.1 channels in complex and passive astrocytes.
Disclosures: X. Tang, None; K. Taniguchi, None; P. Kofuji , None.