Role of potassium and calcium in the generation of cellular bursts in the
dentate gyrus.
Enhui Pan and Janet L. Stringer.
Department of Pharmacology and Division of Neuroscience, Baylor College of
Medicine, One Baylor Plaza, Houston, TX 77030.
APStracts 4:0035N, 1997.
ABSTRACT
Epileptiform activity, which appears to be endogenous, has been recorded in
the granule cells of the dentate gyrus before the onset of synchronized
seizure activity and has been termed cellular bursts. It has been postulated
that an increase in input to the dentate gyrus causes a local increase in
[K+]o and a decrease in [Ca++]o that results in this cellular bursting. The
first test of this hypothesis is to determine whether the cellular bursts
appear in ionic conditions that occur in vivo before the onset of synchronized
epileptic activity. This hypothesis was tested in vitro by varying the ionic
concentrations in the perfusing solution and recording changes in the granule
cells of the dentate gyrus. Intra- and extracellular recordings were made in
the dentate gyrus of hippocampal slices prepared from anesthetized adult
Sprague-Dawley rats. Increasing the extracellular potassium or decreasing the
extracellular calcium of the perfusing solution caused three forms of
spontaneous activity to appear: depolarizing potentials, action potentials and
cellular bursts. Increasing potassium or decreasing calcium also caused the
granule cells to depolarize and reduced their input resistance. No
synchronized extracellular field activity was detected. Simultaneously
increasing potassium and decreasing calcium caused cellular bursts to appear
at concentrations recorded in vivo before the onset of synchronized
reverberatory seizure activity.
Received 27 August 1996; accepted in final form 9 January 1997.
APS Manuscript Number J689-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 5 February 1997