Diversity of voltage-gated calcium currents in large diameter embryonic mouse sensory neurons

• Published in: Neuroscience 1995-11, Vol.69 (2), p.627-641
• Main Authors: Diochot, S., Richard, S., Valmier, J.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; calcium channels; Calcium Channels - physiology; dorsal root ganglion; DRG; EDTA; EGTA; Embryology: invertebrates and vertebrates. Teratology; embryonic day; ethylenediaminetetra-acetate; ethyleneglycolbis (aminoethyl ether) tetra-acetate; Experimental organogenesis; Fundamental and applied biological sciences. Psychology; Ganglia, Spinal - physiology; HEPES; high-voltage-activated; HVA; low-voltage activated; LVA; Membrane Potentials - physiology; Mice; Mice, Inbred Strains; N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid; Neurons, Afferent - physiology; Organogenesis. Physiological fonctions; Patch-Clamp Techniques; TEA; tetraethylammonium; Time Factors; toxins; ω-Aga-IVA; ω-agatoxin IVA; ω-conotoxin GVIA; ω-conotoxin MVIIC; ω-CTx-GVIA; ω-CTx-MVIIC
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/0306-4522(95)00267-M

Voltage-gated Ca 2+ currents were investigated in a subpopulation of dorsal root ganglion neurons (large diameter, neurofilament-positive) acutely isolated from 13-day-old mouse embryos and recorded using the whole-cell patch-clamp technique. Low- and high-voltage-activated calcium currents were recorded. These currents could be identified and separated by their distinct (i) threshold of activation, (ii) ability to run-up during the early phase of recording and (iii) decay kinetics using Ba 2+ instead of Ca 2+ as the charge carrier. Among high-voltage-activated currents, L-, N- and P-type Ca 2+ currents were identified by their sensitivity to, respectively, the dihydropyridine agonist Bay K 8644 (5 μM) and antagonist nitrendipine (3 μM), ω-conotoxin GVIA (3 μM) and ω-agotoxin IVA (30 nM). In the combined presence of nitrendipine (3 μM), ω-conotoxin GVIA (3 μM) and ω-agotoxin IVA (30 nM), two additional high-voltage-activated components were detected. One, blocked by 500 nM ω-conotoxin MVIIC and 1 μM ω-agotoxin IVA, had properties similar to those of the Q-type Ca 2+ current first reported in cerebellar granule cells. The other, defined by its resistance to saturating concentrations of all the blockers mentioned above applied in combination, resembles the R-type Ca 2+ current also described in cerebellar granule cells. In conclusion, embryonic sensory neurons appear to express a large repertoire of voltage-activated Ca 2+ currents with distinct pharmacological properties. This diversity suggests a great variety of pathways for Ca 2+ signaling which may support different functions during development.