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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)
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)
1. In this study we pose the question of why the bovine adrenal medullary chromaffin cell needs various subtypes (L, N, P, Q) of the neuronal high-voltage activated Ca2+ channels to control a given physiological function, i.e. the exocytotic release of catecholamines. One plausible hypothesis is that Ca2+ channel subtypes undergo different patterns of(More)
Mitochondria play an important role in the homeostasis of intracellular Ca(2+) and regulate its availability for exocytosis. Inhibitors of mitochondria Ca(2+) uptake such as protonophore CCCP potentiate the secretory response to a depolarizing pulse of K(+). Exposure of cells to agents that directly (cytochalasin D, latrunculin B) or indirectly (PMA)(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)
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)
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)