Acetylcholine controls GABA-, glutamate-, and glycine-dependent giant depolarizing potentials that govern spontaneous motoneuron activity at the onset of synaptogenesis in the mouse embryonic spinal cord.
A remarkable feature of early neuronal networks is their endogenous ability to generate spontaneous rhythmic electrical activity independently of any external stimuli. In the mouse embryonic SC, this activity starts at an embryonic age of ∼ 12 d and is characterized by bursts of action potentials recurring every 2-3 min. Although these bursts have been extensively studied using extracellular recordings and are known to play an important role in motoneuron (MN) maturation, the mechanisms driving MN activity at the onset of synaptogenesis are still poorly understood. Because only cholinergic antagonists are known to abolish early spontaneous activity, it has long been assumed that spinal cord (SC) activity relies on a core network of MNs synchronized via direct cholinergic collaterals. Using a combination of whole-cell patch-clamp recordings and extracellular recordings in E12.5 isolated mouse SC preparations, we found that spontaneous MN activity is driven by recurrent giant depolarizing potentials. Our analysis reveals that these giant depolarizing potentials are mediated by the activation of GABA, glutamate, and glycine receptors. We did not detect direct nAChR activation evoked by ACh application on MNs, indicating that cholinergic inputs between MNs are not functional at this age. However, we obtained evidence that the cholinergic dependency of early SC activity reflects a presynaptic facilitation of GABA and glutamate synaptic release via nicotinic AChRs. Our study demonstrates that, even in its earliest form, the activity of spinal MNs relies on a refined poly-synaptic network and involves a tight presynaptic cholinergic regulation of both GABAergic and glutamatergic inputs.
Institut National de la Santé et de la Recherche Médicale, Unité Mixte de Recherche S1130, Université Pierre et Marie Curie, Paris, Ile de France, France, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8246, Université Pierre et Marie Curie, Ile de France, France, Université Pierre et Marie Curie UM CR18 Université Paris 06, Ile de France, France, Université d'Angers, 49000 Angers, France, Université de Bordeaux, Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, Unité Mixte de Recherche 5287, F-33000 Bordeaux, France, and Centre National de la Recherche Scientifique, Institut de Neurosciences Cognitives et Intégratives d'Aquitaine, Unité Mixte de Recherche 5287, F-33000 Bordeaux, France.
Antonny
A
Czarnecki
Hervé
H
Le Corronc
Chiara
C
Rigato
Barbara
B
Le Bras
François
F
Couraud
Anne-Laure
AL
Scain
Anne-Emilie
AE
Allain
Christine
C
Mouffle
Erika
E
Bullier
Jean-Marie
JM
Mangin
Pascal
P
Branchereau
Pascal
P
Legendre
D000109:Acetylcholine / Q000378:metabolism* / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D018678:Cholinergic Agents / Q000494:pharmacology; D004622:Embryo, Mammalian; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D005260:Female; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D005998:Glycine / Q000378:metabolism* / Q000494:pharmacology; D018398:Homeodomain Proteins / Q000235:genetics; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D013116:Spinal Cord / Q000166:cytology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
D018678:Cholinergic Agents; D018683:Excitatory Amino Acid Agents; D018398:Homeodomain Proteins; D014157:Transcription Factors; C084059:Hb9 protein, mouse; D018698:Glutamic Acid; D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D000109:Acetylcholine; D005998:Glycine
embryo; giant depolarizing potential; motoneuron; mouse; spinal cord; synaptogenesis