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This Article Full Text Full Text (PDF) All Versions of this Article: 574/1/245    most recent jphysiol.2006.108738v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Balland, B. Articles by Tell, F. Search for Related Content PubMed PubMed Citation Articles by Balland, B. Articles by Tell, F. Related Collections Neuroscience

¹ Laboratoire de Neurophysiologie Cellulaire, CNRS UMR 6150, IFR Jean-Roche, Faculté de Médecine, Bd Pierre Dramard, 13916 Marseille cedex 20, France

Calcium influxes through ionotropic glutamate receptors (AMPA and NMDA receptors, AMPARs and NMDARs) are considered to be critical for the shaping and refinement of neural circuits during synaptogenesis. Using a combined morphological and electrophysiological approach, we evaluated this hypothesis at the level of the nucleus tractus solitarii (NTS), a brainstem structure that is a gateway for many visceral sensory afferent fibres. We confirmed that in the NTS, the first excitatory synapses appeared at embryonic day 18. We next characterized the biophysical properties of NTS AMPARs. Throughout perinatal development, both evoked and miniature EPSCs recorded in the presence of an NMDAR blocker were insensitive to polyamines and had linear current–voltage relationships. This demonstrated that AMPARs at NTS excitatory synapses were calcium-impermeable receptors composed of a majority of GluR₂ subunits. We then investigated the influence of calcium influxes through NMDARs on the development of NTS synaptic transmission. We found that NMDAR expression at synaptic sites did not precede AMPAR expression. Moreover, NMDAR blockade in utero did not prevent the development of AMPAR synaptic currents and the synaptic clustering of GluR₂ subunits. Thus, our data support an alternative model of synaptogenesis that does not depend on calcium influxes through either AMPARs or NMDARs. This model may be particularly relevant to the formation of neural networks devoted to basic behaviours required at birth for survival.

(Received 5 April 2006; accepted after revision 5 May 2006; first published online 11 May 2006)
Corresponding author Fabien Tell: Laboratoire de Neurophysiologie Cellulaire, CNRS UMR 6150, IFR Jean-Roche, Faculté de Médecine, Bd Pierre Dramard, 13916 Marseille cedex 20, France. Email: tell.f{at}jean-roche.Univ-mrs.fr

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