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Methyllycaconitine (MLA), alpha-conotoxin ImI, and alpha-bungarotoxin inhibited the release of catecholamines triggered by brief pulses of acetylcholine (ACh) (100 microM, 5 s) applied to fast-superfused bovine adrenal chromaffin cells, with IC50s of 100 nM for MLA and 300 nM for alpha-conotoxin ImI and alpha-bungarotoxin. MLA (100 nM), alpha-conotoxin ImI(More)
During fast superfusion of bovine chromaffin cells with normal Krebs-HEPES solution containing 2 mM Ca2+, pulses of 100 microM ACh or 100 mM K+ of increasing duration (1-5 s) caused similar exocytosis of about 3-4 microC catecholamine. Depletion of endoplasmic reticulum (ER) Ca2+ by pretreatment with 1 microM thapsigargin, 10 mM caffeine and 10 microM(More)
In chromaffin cells, plasma membrane calcium (Ca2+) channels and mitochondria constitute defined functional units controlling the availability of Ca2+ nearby exocytotic sites. We show here that, when L-/N-type Ca2+ channels were inhibited with nisoldipine and omega-conotoxin GVIA, cytosolic [Ca2+] ([Ca2+]c) peaks measured in fura-4F-loaded cells were(More)
Ca(2+) uptake by mitochondria is a potentially important buffering system able to control cytosolic [Ca(2+)]. In chromaffin cells, we have shown previously that stimulation of either Ca(2+) entry or Ca(2+) release via ryanodine receptors triggers large increases in mitochondrial [Ca(2+)] ([Ca(2+)](M)) approaching the millimolar range, whose blockade(More)
Nanomolar concentrations of atropine have been considered up to now to be selective for blockade of muscarinic receptors for acetylcholine. A collateral finding indicated to us that these low concentrations of atropine could also target the neuronal nicotinic receptors. We report here a detailed study on this novel property of atropine. Catecholamine(More)
The activity of the plasmalemmal Na(+)/Ca(2+) exchanger (NCX) is highly sensitive to temperature. We took advantage of this fact to explore here the effects of the NCX blocker KB-R7943 (KBR) at 22 and 37°C on the kinetics of Ca(2+) currents (ICa), cytosolic Ca(2+) ([Ca(2+)]c) transients, and catecholamine release from bovine chromaffin cells (BCCs)(More)
In bovine chromaffin cells fast-superfused with Krebs-HEPES solution containing 1-2 mM Ca2+, 5 s pulses of choline (1-10 mM), elicited catecholamine secretory responses that were only approximately 10% of those evoked by ACh (0.01-0.1 mM). However, in high-Ca2+ solutions (10-20 mM) the size of the choline secretory responses approached those of ACh. The(More)
The blockade of exocytosis induced by the putative endogenous ligand for imidazoline receptors, agmatine, was studied by using on-line measurement of catecholamine release in bovine adrenal medullary chromaffin cells. Agmatine inhibited the acetylcholine-evoked release of catecholamines in a concentration-dependent manner (IC(50)=366 microM); the(More)
Galantamine is a drug in clinical use for the treatment of Alzheimer's disease, but its mechanism(s) of action remains controversial. Here we addressed the question whether galantamine could potentiate neurotransmitter release by inhibiting small conductance Ca2+ -activated K+ channels (KCa2). Galantamine potentiated catecholamine secretory responses(More)
The mechanism of blockade of P/Q Ca(2+) channels by antimigraine, dotarizine, was studied in voltage-clamped bovine adrenal chromaffin cells. Inward currents through P/Q channels were pharmacologically isolated by superfusing the cells with omega-conotoxin GVIA (1 microM) plus nifedipine (3 microM). Dotarizine (10-30 microM) blocked the P/Q fraction of(More)