Release of glutamate by the embryonic spinal motoneurons of rat positively regulated by acetylcholine through the nicotinic and muscarinic receptors.
It has been shown that mature neurons in adult vertebrates can co-express glutamate and acetylcholine. Furthermore, interactions at the synaptic level have been demonstrated. In a previous study we found that also motoneurons at early embryonic stages, thus well prior to synapse formation, release acetylcholine, and that glutamate increases this release. We now report the existence of a glutamate release from embryonic motoneurons and the increase of glutamate release by acetylcholine. This effect is mediated by nicotinic and muscarinic cholinergic receptors present on embryonic motoneurons. Using conditions of partial or total depletion of calcium, we show that the glutamate release has two components: one is calcium-dependent and the other calcium-independent. Furthermore, we show that extracellular glutamate can be taken up by motoneurons, probably via the neuronal glutamate transporter EAAC1, which we find to be expressed at this stage. Monitoring of the glutamate release kinetics showed that extracellular glutamate concentration reached a steady-state level, strongly suggesting the establishment of equilibrium between glutamate release and uptake. Altogether, these results support the idea that glutamate can act as a neurotransmitter in embryonic motoneurons. We hypothesise that, glutamate acts as a regulator of motoneuron maturation and spinal cord development.
Barthélémy-Requin
M
M
IMVT, IBDML, UMR-CNRS 6216, Parc Scientifique et Technologique de Luminy, Case 907, 13288 Marseille Cedex 09, France. magali.barthelemy@ibdml.univ-mrs.fr
Bévengut
M
M
Portalier
P
P
Ternaux
J P
JP
D000109:Acetylcholine / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D002021:Buffers; D002118:Calcium / Q000494:pharmacology; D050580:Excitatory Amino Acid Transporter 3 / Q000235:genetics; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D009046:Motor Neurons / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology* / Q000196:embryology / Q000254:growth & development
D002021:Buffers; D050580:Excitatory Amino Acid Transporter 3; D010880:Piperidines; D011976:Receptors, Muscarinic; D011978:Receptors, Nicotinic; C493398:Slc1a1 protein, rat; D018698:Glutamic Acid; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium; D000109:Acetylcholine; D002118:Calcium