Developmental regulation of T-, N- and L-type calcium currents in mouse embryonic sensory neurones.
We investigated the development of a low (T-type) and two high voltage-activated (N- and L-type) calcium channel currents in large diameter dorsal root ganglion neurones acutely isolated from embryonic mice using the whole-cell patch-clamp technique. The low and high voltage-activated barium currents (LVA and HVA) were identified by their distinct threshold of activation and their sensitivity to pharmacological agents, dihydropyridines and omega-conotoxin-GVIA, at embryonic day 13 (E13), E15 and E17-18, respectively, before, during and after synaptogenesis. The amplitude and density of LVA currents, measured during a -40 mV pulse from a holding potential of -100 mV, increased significantly between E13 and E15, and remained constant between E15 and E17-18. The density of global HVA current, elicited by 0 mV pulse, increased between E13 and E15/E17-18. The density of the N-type current studied by the application of omega-conotoxin-GVIA (1 microM) increased significantly between E13 and E15/E17-18. The use of the dihydropyridine nitrendipine (1 microM) revealed that the density of L-type current remained constant at each stage of development. Nevertheless, application of dihydropyridine Bay K 8644 (3 microM) demonstrated a significant slowing of the deactivation tail current between embryonic days 13 and 15, which may reflect a qualitative maturation of this class of calcium channel current. The temporal relationship between the changes in calcium channel pattern and the period of target innervation suggests possible roles of T-, N- and L-type currents during developmental key events such as natural neurone death and onset of synapse formation.
Desmadryl
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G
INSERM U432 Neurobiologie et Développement du Système Vestibulaire, Montpellier, France.
Hilaire
C
C
Vigues
S
S
Diochot
S
S
Valmier
J
J
D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D004558:Electric Stimulation; D004594:Electrophysiology; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000196:embryology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D013116:Spinal Cord / Q000166:cytology / Q000196:embryology* / Q000378:metabolism
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels