EFFECTS OF MAGNESIUM-FREE MEDIUM ON INTRINSIC PROPERTIES OF RAT AND HUMAN HIPPOCAMPAL CA1 NEURONS IN VITRO
Abstract number :
3.051
Submission category :
Year :
2002
Submission ID :
3245
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Andrea A. Tavares, Simone D. Salamoni, Gisele F. Finckler, Ricardo V. Breda, Andre F. Palmini, Nei V. Azambuja, Eliseu Paglioli-Neto, Jaderson C. DaCosta. Department of Internal Medicine,Division of Neurology, School of Medicine/Hospital Sao Lucas PUCRS,
RATIONALE: N-Methil-D-Aspartate (NMDA) glutamate receptors may contribute significantly to epileptiform activity induced by magnesiun-free medium recognized in vitro model for the study of eplepsy. Electrophysiological recordings from brain slices perfused with Magnesium-free Ringer solution show interictal and ictal-like seizure discharges. The aim of this study is to test the hypothesis that NMDA-receptors would alter eletrophysiological propertie of CA1 hippocampal neurons in both rats and human tissue.
METHODS: Hippocampal slices were prepared from adult male Wistar rats and surgical samples of human tissue. The rats were decapitated under deep ether anesthesia, the brains quickly removed and 400-mm-thick slices were prepared. The hippocampal human tissues were cut into 500-um-thick sections. The slices were kept in a prechamber at room temperature in Ringer which was continuously bubbled with 95% O2, 5% CO2. The slices were then transferred into an interface recording chamber continuously perfused with an oxygenated Ringer solution. Intracellular recordings were obtained from CA1 pyramidal neurons of control adult wistar rats , pilocarpine induced epileptic rats and human hipoccampal tissue. Ictal-like activity and interictal discharges were induced by perfusing the slice with oxygenated Mg2+-free Ringers solution. Passive (membrane potential, input resistence, time constant) and firing properties (excitability, threshold, amplitude and duration of the spikes) were analysed before, during and after perfusion with Mg2+-free medium.
RESULTS: The control (40 cells) and epileptic (22 cells) rats show significant differences in some intrinsic electrophysiological properties such as membrane potentials and excitability in every moment studied. Also, the control rats show significant differences in the input resistence comparing the periods before, during and after perfusion. These neurones displayed spountaneous single spike and/or bursts of action potentials. On the other hand, only 25% of human hippocampal neurons showed ep[iacute]leptiform activity induced by Mg2+-free medium and none of them had altered its electrophysiological properties.
CONCLUSIONS: Our data suggest that NMDA receptor activation with Mg2+-free medium can induce electrophysiological changes in hippocampal neurons but not in human ones.
[Supported by: CAPES, CNPq, FAPERGS, PUCRS,Secretaria de C&T do RS.]