Differential plasticity of the GABAergic and glycinergic synaptic transmission to rat lumbar motoneurons after spinal cord injury.

Abstract

Maturation of inhibitory postsynaptic transmission onto motoneurons in the rat occurs during the perinatal period, a time window during which pathways arising from the brainstem reach the lumbar enlargement of the spinal cord. There is a developmental switch in miniature IPSCs (mIPSCs) from predominantly long-duration GABAergic to short-duration glycinergic events. We investigated the effects of a complete neonatal [postnatal day 0 (P0)] spinal cord transection (SCT) on the expression of Glycine and GABA(A) receptor subunits (GlyR and GABA(A)R subunits) in lumbar motoneurons. In control rats, the density of GlyR increased from P1 to P7 to reach a plateau, whereas that of GABA(A)R subunits dropped during the same period. In P7 animals with neonatal SCT (SCT-P7), the GlyR densities were unchanged compared with controls of the same age, while the developmental downregulation of GABA(A)R was prevented. Whole-cell patch-clamp recordings of mIPSCs performed in lumbar motoneurons at P7 revealed that the decay time constant of miniature IPSCs and the proportion of GABAergic events significantly increased after SCT. After daily injections of the 5-HT(2)R agonist DOI, GABA(A)R immunolabeling on SCT-P7 motoneurons dropped down to values reported in control-P7, while GlyR labeling remained stable. A SCT made at P5 significantly upregulated the expression of GABA(A)R 1 week later with little, if any, influence on GlyR. We conclude that the plasticity of GlyR is independent of supraspinal influences whereas that of GABA(A)R is markedly influenced by descending pathways, in particular serotoninergic projections.

• Authors: Karina Sadlaoud, Sabrina Tazerart, Cécile Brocard, Céline Jean-Xavier, Paule Portalier, Frédéric Brocard, Laurent Vinay, Hélène Bras
• Journal: The Journal of neuroscience : the official journal of the Society for Neuroscience (J Neurosci) Vol. 30 Issue 9 Pg. 3358-69 (Mar 03 2010) ISSN: 1529-2401 [Electronic] United States
• PMID: 20203195 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Protein Subunits
• Receptors, GABA-A
• Receptors, Glycine
• gamma-Aminobutyric Acid
• Glycine

Topics

• Animals
• Animals, Newborn
• Brain Stem (growth & development)
• Disease Models, Animal
• Down-Regulation (physiology)
• Efferent Pathways (cytology, growth & development, injuries)
• Glycine (metabolism)
• Immunohistochemistry
• Inhibitory Postsynaptic Potentials (physiology)
• Male
• Motor Neurons (metabolism)
• Neural Inhibition (physiology)
• Neuronal Plasticity (physiology)
• Patch-Clamp Techniques
• Protein Subunits (metabolism)
• Rats
• Rats, Wistar
• Receptors, GABA-A (metabolism)
• Receptors, Glycine (metabolism)
• Spinal Cord (cytology, growth & development)
• Spinal Cord Injuries (metabolism, physiopathology)
• Synaptic Transmission (physiology)
• Up-Regulation (physiology)
• gamma-Aminobutyric Acid (metabolism)