title: Paradoxical facilitation of exocytosis by inhibition of L-type calcium channels of bovine chromaffin cells.
abstract: Ca(2+) entry through the L-subtype (α(1D), Ca(v)1,3) of voltage-dependent calcium channels (VDCCs) seems to selectively regulate the endocytotic response after the application of a single depolarizing pulse to voltage-clamped bovine chromaffin cells. Here we have found that L channel blockade with nifedipine transformed the exocytotic responses elicited by a double-pulse protocol, from depression to facilitation. This apparent paradoxical effect was mimicked by pharmacological interventions that directly block endocytosis namely, dynasore, calmidazolium, GTP-γS and GDP-βS. This reinforces our view that Ca(2+) entry through PQ channels (α(1A); Ca(v)2.1) regulates fast exocytosis while Ca(2+) entry through L channels preferentially controls rapid endocytosis.
authors.affiliation: Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: Juliana M
authors.initials: JM
authors.lastname: Rosa
authors.forename: Marina
authors.initials: M
authors.lastname: Conde
authors.forename: Carmen
authors.initials: C
authors.lastname: Nanclares
authors.forename: Angela
authors.initials: A
authors.lastname: Orozco
authors.forename: Inés
authors.initials: I
authors.lastname: Colmena
authors.forename: Ricardo
authors.initials: R
authors.lastname: de Pascual
authors.forename: Antonio G
authors.initials: AG
authors.lastname: García
authors.forename: Luis
authors.initials: L
authors.lastname: Gandía
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects* / Q000378:metabolism; D005089:Exocytosis / Q000187:drug effects*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000031:analogs & derivatives / Q000494:pharmacology; D006835:Hydrazones / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D006835:Hydrazones; D007093:Imidazoles; C511794:N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide; C034883:guanosine 5'-O-(2-thiotriphosphate); D016244:Guanosine 5'-O-(3-Thiotriphosphate); C031938:calmidazolium; D009543:Nifedipine; D002118:Calcium