title: omega-Agatoxin IVA blocks nicotinic receptor channels in bovine chromaffin cells.
abstract: We have studied the contribution of P-type voltage-dependent Ca2+ channels to both catacholamine (CA) and ATP secretion from bovine chromaffin cells induced by high K+ or nicotine using omega-agatoxin IVA, a selective blocker of P-type voltage-dependent Ca2+ channels. We found that high K+ (75 mM) induced the release of about 13% of norepinephrine, 5% epinephrine and 11% ATP, and that omega-agatoxin (100 nM) did not affect this secretion. However, both nicotine-induced CA and ATP secretion were significantly blocked (about 50%) by omega-agatoxin IVA (100 nM). In addition, this toxin also reversibly blocked (about 70%) the inward current induced by nicotine in bovine chromaffin cells. The results suggest that, besides its known action of blocking P-type voltage-dependent channels, omega-agatoxin is a potent and reversible blocker of the nicotinic receptor channel in chromaffin cells, and that this action would explain the blockade of nicotine-induced secretion.
authors.affiliation: Departamento de Farmacología, Universidad de Alicante, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Granja
authors.forename: J M
authors.initials: JM
authors.lastname: Fernández-Fernández
authors.forename: V
authors.initials: V
authors.lastname: Izaguirre
authors.forename: C
authors.initials: C
authors.lastname: González-García
authors.forename: V
authors.initials: V
authors.lastname: Ceña
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D004837:Epinephrine / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000378:metabolism; D013111:Spider Venoms / Q000494:pharmacology*; D020867:omega-Agatoxin IVA
chemical_list: D015220:Calcium Channels; D011978:Receptors, Nicotinic; D013111:Spider Venoms; D020867:omega-Agatoxin IVA; D009538:Nicotine; D000255:Adenosine Triphosphate; D011188:Potassium; D009638:Norepinephrine; D004837:Epinephrine