Differential effects of the brainstem on the maturation of GABAergic and glycinergic synapses on lumbar motoneurones in the rat
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1
Universite de la Mediterranee, Laboratoire Plasticite et Physio-Pathologie de la Motricite, UMR 6196 CNRS , France
In immature spinal neurons, GABA- and glycine-evoked potentials are depolarizing and switch to a hyperpolarizing action during the first postnatal week. After neonatal spinal cord transection (SCT), this ontogenetic shift does not occur in lumbar Motoneurones (Mns). We investigated the effects of a complete neonatal SCT on the immuno-expression of Gly and GABAA receptors subunits (GlyR and GABAAR) in lumbar Mns. 7 days-old rats with neonatal SCT (S7) were compared to shams at P1 and P7. On S7, the membrane density of GlyRα1 was unchanged compared to P7. By contrast, the densities of GABAAR α2 and α3 subunits were significantly higher on S7 than on P7, and close to those reported at P1. Whole cell patch clamp recordings of mIPSCs performed in P7 vs S7 lumbar Mns revealed that the decay time of GABA but not glycine events was affected by SCT and the proportion of GABA events significantly increased, whereas the proportion of glycine and mixed events decreased. Serotoninergic axons arising from Raphe nuclei are among the earliest to reach the lumbar segments. Therefore, we tested the effects of a pharmacological activation of 5HT2R by the agonist DOI, which play a key role in the recovery of motor function after SCT, in S7 rats. After DOI treatment, GABAAR motoneuronal immunolabeling dropped down to values reported in P7, while Glyα1 labelling remained stable. We conclude that the plasticity of GlyR is independent of supraspinal influences whereas the plasticity of GABAAR is markedly influenced by descending pathways, in particular serotonergic projections.
Keywords:
GABAA receptors,
glycine receptors,
immunocytochemistry,
spinal cord transection,
whole cell patch recording
Conference:
3rd Mediterranean Conference of Neuroscience , Alexandria, Egypt, 13 Dec - 16 Dec, 2009.
Presentation Type:
Poster Presentation
Citation:
Sadlaoud
K,
Tazerart
S,
Brocard
C,
Jean-Xavier
C,
Portalier
P,
Brocard
F,
Vinay
L and
Bras
H
(2009). Differential effects of the brainstem on the maturation of GABAergic and glycinergic synapses on lumbar motoneurones in the rat.
Front. Neurosci.
Conference Abstract:
3rd Mediterranean Conference of Neuroscience .
doi: 10.3389/conf.neuro.01.2009.16.165
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Received:
26 Nov 2009;
Published Online:
26 Nov 2009.
*
Correspondence:
Karina Sadlaoud, Universite de la Mediterranee, Laboratoire Plasticite et Physio-Pathologie de la Motricite, UMR 6196 CNRS, 13331 Marseille, France, bras@dpm.cnrs-mrs.fr