title: Voltage-independent inhibition of Ca(V)2.2 channels is delimited to a specific region of the membrane potential in rat SCG neurons.
abstract: Neurotransmitters and hormones regulate Ca(V)2.2 channels through a voltage-independent pathway which is not well understood. It has been suggested that this voltage-independent inhibition is constant at all membrane voltages. However, changes in the percent of voltage-independent inhibition of Ca(V)2.2 have not been tested within a physiological voltage range. Here, we used a double-pulse protocol to isolate the voltage-independent inhibition of Ca(V)2.2 channels induced by noradrenaline in rat superior cervical ganglion neurons. To assess changes in the percent of the voltage-independent inhibition, the activation voltage of the channels was tested between -40 and +40 mV. We found that the percent of voltage-independent inhibition induced by noradrenaline changed with the activation voltage used. In addition, voltage-independent inhibition induced by oxo-M, a muscarinic agonist, exhibited the same dependence on activation voltage, which supports that this pattern is not exclusive for adrenergic activation. Our results suggested that voltage-independent inhibition of Ca(V)2.2 channels depends on the activation voltage of the channel in a physiological voltage range. This may have relevant implications in the understanding of the mechanism involved in voltage-independent inhibition.
authors.affiliation: Department of Physiology,  School of Medicine,  Universidad Nacional Autónoma de México, UNAM. Apartado Postal 70250, México D.F. C.P. 04510,  México.
authors.forename: Oscar
authors.initials: O
authors.lastname: Vivas
authors.forename: Isabel
authors.initials: I
authors.lastname: Arenas
authors.forename: David E
authors.initials: DE
authors.lastname: García
mesh_terms: D000818:Animals; D020864:Calcium Channels, N-Type / Q000187:drug effects*; D002478:Cells, Cultured; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects*; D018721:Muscarinic Agonists / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010095:Oxotremorine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017783:Superior Cervical Ganglion / Q000502:physiology*
chemical_list: C503279:Cacna1b protein, rat; D020864:Calcium Channels, N-Type; D018721:Muscarinic Agonists; D010095:Oxotremorine; C042743:oxotremorine M; D009638:Norepinephrine