Immunocytochemical localization of small-conductance, calcium-dependent potassium channels in astrocytes of the rat supraoptic nucleus
Article first published online: 30 AUG 2005
Copyright © 2005 Wiley-Liss, Inc.
Journal of Comparative Neurology
Volume 491, Issue 3, pages 175–185, 24 October 2005
How to Cite
Armstrong, W. E., Rubrum, A., Teruyama, R., Bond, C. T. and Adelman, J. P. (2005), Immunocytochemical localization of small-conductance, calcium-dependent potassium channels in astrocytes of the rat supraoptic nucleus. J. Comp. Neurol., 491: 175–185. doi: 10.1002/cne.20679
- Issue published online: 30 AUG 2005
- Article first published online: 30 AUG 2005
- Manuscript Accepted: 12 MAY 2005
- Manuscript Revised: 25 APR 2005
- Manuscript Received: 25 FEB 2005
- National Institutes of Health. Grant Numbers: NS-23941, HD-41002, NS-38880
- glial fibrillary acidic protein;
Supraoptic nucleus (SON) neurons possess a prominent afterhyperpolarization (AHP) that contributes to spike patterning. This AHP is probably underlain by a small-conductance, CA2+-dependent, K+ type 3 (SK3) channel. To determine the distribution of SK3 channels within the SON, we used immunocytochemistry in rats and in transgenic mice with a regulatory cassette on the SK3 gene, allowing regulated expression with dietary doxycycline (DOX). In rats and wild-type mice, SK3 immunostaining revealed an intense lacy network surrounding SON neurons, with weak staining in neuronal somata and dendrites. In untreated, conditional SK3 knockout mice, SK3 was overexpressed, but the pericellular pattern in the SON was similar to that of rats. DOX-treated transgenic mice exhibited no SK3 staining in the SON. Double staining for oxytocin or vasopressin neurons revealed weak co-localization with SK3 but strong staining surrounding each neuron type. Electron microscopy showed that SK3-like immunoreactivity was intense between neuronal somata and dendrites, in apparent glial processes, but weak in neurons. This was confirmed by using confocal microscopy and double staining for glial fibrillary acidic protein (GFAP) and SK3: many GFAP-positive processes in the SON, and in the ventral dendritic/glial lamina, were shown to contain SK3-like immunoreactivity. These studies suggest a prominent role of SK3 channels in astrocytes. Given the marked plasticity in glial/neuronal relationships, as well as studies suggesting that astrocytes in the central nervous system can generate prominent CA2+ transients to various stimuli, a CA2+-dependent K+ channel may help SON astrocytes with K+ buffering whenever astrocyte intracellular CA2+ is increased. J. Comp. Neurol. 491:175–185, 2005. © 2005 Wiley-Liss, Inc.