title: Nanosecond electric pulses: a novel stimulus for triggering Ca2+ influx into chromaffin cells via voltage-gated Ca2+ channels.
abstract: Exposing bovine chromaffin cells to a single 5 ns, high-voltage (5 MV/m) electric pulse stimulates Ca(2+) entry into the cells via L-type voltage-gated Ca(2+) channels (VGCC), resulting in the release of catecholamine. In this study, fluorescence imaging was used to monitor nanosecond pulse-induced effects on intracellular Ca(2+) level ([Ca(2+)](i)) to investigate the contribution of other types of VGCCs expressed in these cells in mediating Ca(2+) entry. ω-Conotoxin GVIA and ω-agatoxin IVA, antagonists of N-type and P/Q-type VGCCs, respectively, reduced the magnitude of the rise in [Ca(2+)](i) elicited by a 5 ns pulse. ω-conotoxin MVIIC, which blocks N- and P/Q-type VGCCs, had a similar effect. Blocking L-, N-, and P\Q-type channels simultaneously with a cocktail of VGCC inhibitors abolished the pulse-induced [Ca(2+)](i) response of the cells, suggesting Ca(2+) influx occurs only via VGCCs. Lowering extracellular K(+) concentration from 5 to 2 mM or pulsing cells in Na(+)-free medium suppressed the pulse-induced rise in [Ca(2+)](i) in the majority of cells. Thus, both membrane potential and Na(+) entry appear to play a role in the mechanism by which nanoelectropulses evoke Ca(2+) influx. However, activation of voltage-gated Na(+) channels (VGSC) is not involved since tetrodotoxin (TTX) failed to block the pulse-induced rise in [Ca(2+)](i). These findings demonstrate that a single electric pulse of only 5 ns duration serves as a novel stimulus to open multiple types of VGCCs in chromaffin cells in a manner involving Na(+) transport across the plasma membrane. Whether Na(+) transport occurs via non-selective cation channels and/or through lipid nanopores remains to be determined.
authors.affiliation: Department of Pharmacology, University of Nevada School of Medicine, Howard Building/MS 318, Reno, NV 89557, USA. gcraviso@medicine.nevada.edu
authors.forename: Gale L
authors.initials: GL
authors.lastname: Craviso
authors.forename: Sophie
authors.initials: S
authors.lastname: Choe
authors.forename: Paroma
authors.initials: P
authors.lastname: Chatterjee
authors.forename: Indira
authors.initials: I
authors.lastname: Chatterjee
authors.forename: P Thomas
authors.initials: PT
authors.lastname: Vernier
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002417:Cattle; D019439:Chromaffin Cells / Q000378:metabolism*; D004560:Electricity; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D012964:Sodium / Q000378:metabolism; D013997:Time Factors
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D012964:Sodium; D002118:Calcium