Chapter

Seizure-Induced Formation of Basal Dendrites on Granule Cells of the Rodent Dentate Gyrus

Charles E. Ribak, Lee A. Shapiro, Xiao-Xin Yan, Khashayar Dashtipour, J. Victor Nadler, Andre Obenaus, Igor Spigelman and Paul S. Buckmaster

in Jasper's Basic Mechanisms of the Epilepsies

Fourth edition

Published on behalf of ©Jeffrey L. Noebels, Massimo Avoli, Michael A. Rogawski, Richard W. Olsen, and Antonio V. Delgado-Escueta

Published in print July 2012 | ISBN: 9780199746545
Published online April 2013 | e-ISBN: 9780199322817 | DOI: http://dx.doi.org/10.1093/med/9780199746545.003.0036

Series: Contemporary Neurology Series

Seizure-Induced Formation of Basal Dendrites on Granule Cells of the Rodent Dentate Gyrus

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Granule cells of the normal adult rodent dentate gyrus generally have the typical morphology of bipolar cells. Their apical dendrites arise from one pole and arborize into the molecular layer, while the axon originates from the base of the granule cell body and extends into the hilus subjacent to the granule cell layer.1 Two exceptions to this rule have been observed. Sometimes recurrent basal dendrites arise from the base of granule cell bodies and then curve back through the granule cell layer in the direction of the molecular layer, where they join apical dendrites.2–4 Despite this unusual origination, dendrites of dentate granule cells in rodents arborize exclusively in the molecular layer. The other exception is the rare instance of an axon originating from the granule cell's apical dendrite or the apical pole of its cell body.4 In this instance, the axon descends into the hilus without giving rise to collaterals. Both of these morphologies suggest that rat granule cells are more heterogeneous than was previously indicated. Dentate granule cells from humans and nonhuman primates differ from granule cells from rodents; primate granule cells commonly have basal dendrites. Seress and Mrzljak5 were the first to show that primate granule cells display basal dendrites in normal brain. Other studies confirmed this observation and showed that many granule cells in monkey have basal dendrites that enter the hilus.6 These basal dendrites have large, complex spines and smaller “stubby” spines. About 10% of granule cells in the monkey dentate gyrus exhibit basal dendrites. Pertinent to this review is the finding that greater numbers of granule cells with hilar basal dendrites are found in the temporal lobes of epileptic humans compared to normal human control tissues.7,8 The remainder of this chapter will focus on the seizure-induced formation of hilar basal dendrites in rodents and the potential significance of hilar basal dendrites in epileptogenesis.

Chapter.  5963 words.  Illustrated.

Subjects: Neurology

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