title: Voltage-dependent inhibition and facilitation of Ca channel activation by GTP-gamma-S and Ca-agonists in adult rat sensory neurons.
abstract: Intracellular application of guanosine 5'-O-3-thiotriphosphate (GTP-gamma-S, 100 microM) causes a slow down of high-threshold Ca channel activation in adult rat sensory neurons that is relieved by strong depolarizations or by the Ca agonist Bay K 8644 (5 microM). Recovery from GTP-gamma-S inhibition is usually accompanied by an increase in Ca current amplitude (facilitation) and is insensitive to holding potential (-60 to -90 mV). Inhibition and facilitation of Ca currents are also little affected by nifedipine (5 microM) or by cell incubation with omega-conotoxin (omega-CgTx, 3.2 microM). We conclude that both slowdown of Ca channel activation by GTP-gamma-S and facilitation by strong depolarizations or by Ca agonists derive from a common process in which G-protein activation, membrane voltage and Ca agonist receptors interact to modulate neuronal Ca channel gatings.
authors.affiliation: Department of Anatomy and Human Physiology, Turin, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Pollo
authors.forename: M
authors.initials: M
authors.lastname: Taglialatela
authors.forename: E
authors.initials: E
authors.lastname: Carbone
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects* / Q000502:physiology; D004594:Electrophysiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D008978:Mollusk Venoms / Q000494:pharmacology; D009475:Neurons, Afferent / Q000378:metabolism / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D051381:Rats; D020866:omega-Conotoxin GVIA
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D008978:Mollusk Venoms; D010456:Peptides, Cyclic; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D020866:omega-Conotoxin GVIA; D009543:Nifedipine; D002118:Calcium