Differential plasticity of the GABAergic and glycinergic synaptic transmission to rat lumbar motoneurons after spinal cord injury.
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.
Sadlaoud
Karina
K
Laboratoire Plasticité et Physio-Pathologie de la Motricité (Unité Mixte de Recherche 6196), Centre National de la Recherche Scientifique and Aix-Marseille Université, Marseille, France.
Tazerart
Sabrina
S
Brocard
Cécile
C
Jean-Xavier
Céline
C
Portalier
Paule
P
Brocard
Frédéric
F
Vinay
Laurent
L
Bras
Hélène
H
D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000254:growth & development; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000502:physiology; D004525:Efferent Pathways / Q000166:cytology / Q000254:growth & development* / Q000293:injuries; D005998:Glycine / Q000378:metabolism; D007150:Immunohistochemistry; D053444:Inhibitory Postsynaptic Potentials / Q000502:physiology; D008297:Male; D009046:Motor Neurons / Q000378:metabolism*; D009433:Neural Inhibition / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000378:metabolism; D018009:Receptors, Glycine / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology / Q000254:growth & development*; D013119:Spinal Cord Injuries / Q000378:metabolism* / Q000503:physiopathology; D009435:Synaptic Transmission / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D021122:Protein Subunits; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; D005680:gamma-Aminobutyric Acid; D005998:Glycine