Toxin-resistant calcium currents in embryonic mouse sensory neurons.
We characterized toxin-insensitive calcium currents expressed by acutely dissociated embryonic dorsal root ganglion neurons. In the presence of 3 microM omega-conotoxin-GVIA, 3 microM nitrendipine and either 500 nM omega-agatoxin-IVA or 500 nM omega-conotoxin-MVIIC to inhibit N-, L- and P/Q-type currents, respectively, all neurons expressed two residual currents: a T-type and another which we referred to as toxin-resistant current. The toxin-resistant current (i) consisted of an inactivating and a sustained components, (ii) had a threshold of activation and a steady-state inactivation comprised between that of the T-type current and that of the other high-voltage-activated currents, (iii) had the same permeability for barium and calcium used as charge carriers, (iv) was highly sensitive to both cadmium and nickel; and (v) was insensitive to 500 microM amiloride which abolished the T-type at this concentration. The properties of the toxin-resistant current are very similar to those of the currents expressed in oocytes following injection of alpha(1E) subunits which we demonstrated to be present in these neurons. Therefore a component of the toxin-resistant current calcium channels in sensory neurons may be closely related to those calcium channels formed by alpha(1E) subunits.
Hilaire
C
C
Laboratoire de médecine expérimentale, Institut de Biologie, C.N.R.S.UPR 9008, I.N.S.E.R.M. U 249, Montpellier, France.
Diochot
S
S
Desmadryl
G
G
Richard
S
S
Valmier
J
J
D000818:Animals; D002121:Calcium Channel Blockers / Q000633:toxicity*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D004622:Embryo, Mammalian / Q000187:drug effects / Q000502:physiology; D005727:Ganglia, Spinal / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000633:toxicity; D014118:Toxins, Biological / Q000633:toxicity*; D020960:omega-Conotoxins
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010455:Peptides; D014118:Toxins, Biological; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC