Elementary properties and pharmacological sensitivities of calcium channels in mammalian peripheral neurons.
The major component of whole-cell Ca2+ current in differentiated, neuron-like rat pheochromocytoma (PC12) cells and sympathetic neurons is carried by dihydropyridine-insensitive, high-threshold-activated N-type Ca2+ channels. We show that these channels have unitary properties distinct from those of previously described Ca2+ channels and contribute both slowly inactivating and large sustained components of whole-cell current. The N-type Ca2+ currents are modulated by GTP binding proteins. The snail toxin omega-conotoxin reveals two pharmacological components of N-type currents, one blocked irreversibly and one inhibited reversibly. Contrary to previous reports, neuronal L-type channels are insensitive to omega-conotoxin. N-type Ca2+ channels appear to be specific for neuronal cells, since their functional expression is greatly enhanced by nerve growth factor.
Plummer
M R
MR
Department of Cellular and Molecular Physiology, Harvard Medical School, Boston, Massachusetts 02115.
Logothetis
D E
DE
Hess
P
P
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D004095:Dihydropyridines / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects*; D008978:Mollusk Venoms / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism; D010673:Pheochromocytoma / Q000473:pathology; D051381:Rats; D013873:Thionucleotides / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000378:metabolism; D020960:omega-Conotoxins
D015220:Calcium Channels; D004095:Dihydropyridines; D008978:Mollusk Venoms; D013873:Thionucleotides; D020960:omega-Conotoxins; C053423:Conus magus toxin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C038806:1,4-dihydropyridine; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D000109:Acetylcholine; D002118:Calcium