Electrophysiological and morphological characterization of dentate astrocytes in the hippocampus.
We studied electrophysiological and morphological properties of astrocytes in the dentate gyrus of the rat hippocampus in slices. Intracellular application of Lucifer yellow revealed two types of morphology: one with a long process extruding from the cell body, and the other with numerous short processes surrounding the cell body. Their electrophysiological properties were either passive, that is, no detectable voltage-dependent conductance, or complex, with Na+/K+ currents similar to those reported in the Ammon's horn astrocytes. We did not find any morphological correlate to the types of electrophysiological profile or dye coupling. Chelation of cytoplasmic calcium ([Ca2+]i) by BAPTA increased the incidence of detecting a low Na+) conductance and transient outward K+ currents. However, an inwardly rectifying K+ current (Kir), a hallmark of differentiated CA1/3 astrocytes, was not a representative K+-current in the complex dentate astrocytes, suggesting that these astrocytes could retain an immature form of K-currents. Dentate astrocytes may possess a distinct current profile that is different from those in CA1/3 Ammon's horn.
Isokawa
Masako
M
Department of Physiology, University of Maryland, 655 W. Baltimore Street, Baltimore, Maryland 21201, USA. misok001@yahoo.com
McKhann
Guy M
GM
D000818:Animals; D001253:Astrocytes / Q000166:cytology* / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D048430:Cell Shape; D003600:Cytosol / Q000502:physiology; D018891:Dentate Gyrus / Q000166:cytology* / Q000502:physiology*; D004594:Electrophysiology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009924:Organ Culture Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000502:physiology
D024661:Potassium Channels, Inwardly Rectifying; D015222:Sodium Channels; D012964:Sodium; D002118:Calcium