Neuroscience 2005 Abstract
| Presentation Number: | 516.13 |
|---|---|
| Abstract Title: | Excitatory actions of depolarizing inhibitory postsynaptic potentials in neonatal rat lumbar motoneurons. |
| Authors: |
Jean-Xavier, C.*1
; Cattaert, D.2
; Vinay, L.1
1Plasticité et Physio-Pathologie de la Motricité, CNRS, Marseille, France 2France, CNRS, 31 chemin Joseph Aiguier, F-13402 cx 20, |
| Primary Theme and Topics |
Sensory and Motor Systems - Pattern Generation and Locomotion -- Mammalian locomotion |
| Secondary Theme and Topics | Sensory and Motor Systems<br />- Spinal Cord<br />-- Motoneurons |
| Session: |
516. Pattern Generation and Locomotion: Mammals Poster |
| Presentation Time: | Monday, November 14, 2005 1:00 PM-2:00 PM |
| Location: | Washington Convention Center - Hall A-C, Board # AA34 |
| Keywords: | CHLORIDE, TRANSPORTER, GLYCINE, GABA |
Spinal cord transection on the day of birth in the rat increases the excitability of lumbar networks (Norreel et al., J. Neurosci. 2003) and prevents the typical switch from depolarizing to hyperpolarizing inhibitory post-synaptic potentials (IPSPs) that occurs during the first postnatal week (Jean-Xavier et al., SfN 2004). In the present study we investigated the excitatory role of depolarizing IPSPs, which were recorded either in normal saline solution or after blocking the transporters that regulate the intracellular chloride concentration (bumetanide), thereby inducing a positive shift of the reversal potential of IPSPs (Eipsp). The excitability of the recorded motoneurons was tested by injecting short sub-threshold depolarizing current pulses. Cells were inhibited in the early phase of the depolarizing IPSPs when the conductance increase dominates. However, a facilitation of action potential generation was observed in the late phase of the response when the conductance has returned to control values but the cell is still depolarized. The interaction between depolarizing IPSPs and excitatory inputs was tested by means of a simulation using the compartment model program Neuron. This modeling study confirmed that the shunting action decreases rapidly as the inhibitory inputs are moved away from the soma. In contrast to this local action of the conductance increase, the depolarization spreads electrotonically and may facilitate remote excitatory inputs. This study demonstrates that small depolarizing IPSPs (Eipsp 5-10 mV above resting potential) can, depending on timing and location, promote action potential firing in response to sub-threshold excitatory inputs. Slight changes of the chloride equilibrium potential (between -60 and -75 mV) may therefore have important consequences in spinal cord processing.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
Copyright © 2005-2026 Society for Neuroscience; all rights reserved. Permission to republish any abstract or part of any abstract in any form must be obtained in writing by SfN office prior to publication.
