An activity-dependent neurotrophin-3 autocrine loop regulates the phenotype of developing hippocampal pyramidal neurons before target contact.
Neurotrophin-3 (NT-3), its cognate receptor trkC, and voltage-gated calcium channels are coexpressed by embryonic pyramidal neurons before target contact, but their functions at this stage of development are still unclear. We show here that, in vitro, anti-NT-3 and anti-trkC antibodies blocked the increase, and NT-3 reversed the decrease in the number of calbindin-D(28k)-positive pyramidal neurons induced by, respectively, calcium channel activations and blockades. Similar results were obtained with single-neuron microcultures. In addition, voltage-gated calcium channel inhibition downregulates the extracellular levels of NT-3 in high-density cultures. Moreover, electrophysiological experiments in single-cell cultures reveal a tetrodotoxin-sensitive spontaneous electrical activity allowing voltage-gated calcium channel activation. The mouse NT-3 (-/-) mutation decreases by 40% the number of developing calbindin-D(28k)-positive pyramidal neurons, without affecting neuronal survival, both in vitro and in vivo. Thus, present results strongly support that an activity-dependent autocrine NT-3 loop provides a local, intrinsic mechanism by which, before target contact, hippocampal pyramidal-like neurons may regulate their own differentiation, a role that may be important during early CNS differentiation or after adult target disruption.
Boukhaddaoui
H
H
Institut National de la Santé et de la Recherche Médicale U-432, Universite Montpellier II, 34095 Montpellier, Cedex 5, France.
Sieso
V
V
Scamps
F
F
Valmier
J
J
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D019898:Autocrine Communication / Q000187:drug effects / Q000502:physiology*; D064026:Calbindins; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002452:Cell Count; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008959:Models, Neurological; D020933:Neurotrophin 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010641:Phenotype; D017966:Pyramidal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020812:Receptor, trkC / Q000037:antagonists & inhibitors; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
D000906:Antibodies; D064026:Calbindins; D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D020933:Neurotrophin 3; D064030:S100 Calcium Binding Protein G; D013779:Tetrodotoxin; D020812:Receptor, trkC