Sant'Ambrogio di Torino, Italy
Sant'Ambrogio di Torino, Italy

Time filter

Source Type

Mahapatra S.,NIS Center | Marcantoni A.,NIS Center | Vandael D.H.F.,NIS Center | Striessnig J.,University of Innsbruck | Carbone E.,NIS Center
Channels | Year: 2011

Mouse and rat chromaffin cells (MCCs, RCCs) fire spontaneously at rest and their activity is mainly supported by the two L-type Ca 2+ channels expressed in these cells (Ca v1.2 and Ca v1.3). Using Ca v1.3 -/- KO MCCs we have shown that Ca v1.3 possess all the prerequisites for carrying subthreshold currents that sustain low frequency cell firing near resting (0.5 to 2 Hz at -50 mV): 1 low-threshold and steep voltage dependence of activation, slow and incomplete inactivation during pulses of several hundreds of milliseconds. Ca v1.2 contributes also to pacemaking MCCs and possibly even Na + channels may participate in the firing of a small percentage of cells. We now show that at potentials near resting (-50 mV), Ca v1.3 carries equal amounts of Ca 2+ current to Ca v1.2 but activates at 9 mV more negative potentials. MCCs express only TTX-sensitive Na v1 channels that activate at 24 mV more positive potentials than Ca v1.3 and are fully inactivating. Their blockade prevents the firing only in a small percentage of cells (13%). This suggests that the order of importance with regard to pacemaking MCCs is: Ca v1.3, Ca v1.2 and Na v1. The above conclusions, however, rely on the proper use of DHPs, whose blocking potency is strongly holding potential dependent. We also show that small increases of KCl concentration steadily depolarize the MCCs causing abnormally increased firing frequencies, lowered and broadened AP waveforms and an increased facility of switching "non-firing" into "firing" cells that may lead to erroneous conclusions about the role of Ca v1.3 and Ca v1.2 as pacemaker channels in MCCs. © 2011 Landes Bioscience.


Vandael D.H.F.,NIS Center | Ottaviani M.M.,NIS Center | Legros C.,French Institute of Health and Medical Research | Lefort C.,French Institute of Health and Medical Research | And 4 more authors.
Journal of Physiology | Year: 2015

Key points: Mouse chromaffin cells (MCCs) of the adrenal medulla possess fast-inactivating Nav channels whose availability alters spontaneous action potential firing patterns and the Ca2+-dependent secretion of catecholamines. Here, we report MCCs expressing large densities of neuronal fast-inactivating Nav1.3 and Nav1.7 channels that carry little or no subthreshold pacemaker currents and can be slowly inactivated by 50% upon slight membrane depolarization. Reducing Nav1.3/Nav1.7 availability by tetrodotoxin or by sustained depolarization near rest leads to a switch from tonic to burst-firing patterns that give rise to elevated Ca2+-influx and increased catecholamine release. Spontaneous burst firing is also evident in a small percentage of control MCCs. Our results establish that burst firing comprises an intrinsic firing mode of MCCs that boosts their output. This occurs particularly when Nav channel availability is reduced by sustained splanchnic nerve stimulation or prolonged cell depolarizations induced by acidosis, hyperkalaemia and increased muscarine levels. Action potential (AP) firing in mouse chromaffin cells (MCCs) is mainly sustained by Cav1.3 L-type channels that drive BK and SK currents and regulate the pacemaking cycle. As secretory units, CCs optimally recruit Ca2+ channels when stimulated, a process potentially dependent on the modulation of the AP waveform. Our previous work has shown that a critical determinant of AP shape is voltage-gated sodium channel (Nav) channel availability. Here, we studied the contribution of Nav channels to firing patterns and AP shapes at rest (-50 mV) and upon stimulation (-40 mV). Using quantitative RT-PCR and immunoblotting, we show that MCCs mainly express tetrodotoxin (TTX)-sensitive, fast-inactivating Nav1.3 and Nav1.7 channels that carry little or no Na+ current during slow ramp depolarizations. Time constants and the percentage of recovery from fast inactivation and slow entry into closed-state inactivation are similar to that of brain Nav1.3 and Nav1.7 channels. The fraction of available Nav channels is reduced by half after 10 mV depolarization from -50 to -40 mV. This leads to low amplitude spikes and a reduction in repolarizing K+ currents inverting the net current from outward to inward during the after-hyperpolarization. When Nav channel availability is reduced by up to 20% of total, either by TTX block or steady depolarization, a switch from tonic to burst firing is observed. The spontaneous occurrence of high frequency bursts is rare under control conditions (14% of cells) but leads to major Ca2+-entry and increased catecholamine release. Thus, Nav1.3/Nav1.7 channel availability sets the AP shape, burst-firing initiation and regulates catecholamine secretion in MCCs. Nav channel inactivation becomes important during periods of high activity, mimicking stress responses. © 2014 The Physiological Society.


Vandael D.H.F.,Nis Center | Vandael D.H.F.,AM Technology | Marcantoni A.,Nis Center | Carbone E.,Nis Center
Current Molecular Pharmacology | Year: 2015

Neuronal and neuroendocrine L-type calcium channels (Cav1.2, Cav1.3) open readily at relatively low membrane potentials and allow Ca2+ to enter the cells near resting potentials. In this way, Cav1.2 and Cav1.3 shape the action potential waveform, contribute to gene expression, synaptic plasticity, neuronal differentiation, hormone secretion and pacemaker activity. In the chromaffin cells (CCs) of the adrenal medulla, Cav1.3 is highly expressed and is shown to support most of the pacemaking current that sustains action potential (AP) firings and part of the catecholamine secretion. Cav1.3 forms Ca2+-nanodomains with the fast inactivating BK channels and drives the resting SK currents. These latter set the inter-spike interval duration between consecutive spikes during spontaneous firing and the rate of spike adaptation during sustained depolarizations. Cav1.3 plays also a primary role in the switch from “tonic” to “burst” firing that occurs in mouse CCs when either the availability of voltage-gated Na channels (Nav) is reduced or the β2 subunit featuring the fast inactivating BK channels is deleted. Here, we discuss the functional role of these “neuronlike” firing modes in CCs and how Cav1.3 contributes to them. The open issue is to understand how these novel firing patterns are adapted to regulate the quantity of circulating catecholamines during resting condition or in response to acute and chronic stress. © 2015 Bentham Science Publishers.


Mahapatra S.,NIS Center | Marcantoni A.,NIS Center | Zuccotti A.,University of Tübingen | Carabelli V.,NIS Center | Carbone E.,NIS Center
Journal of Physiology | Year: 2012

Mouse chromaffin cells (MCCs) express high densities of L-type Ca 2+ channels (LTCCs), which control pacemaking activity and catecholamine secretion proportionally to their density of expression. In vivo phosphorylation of LTCCs by cAMP-PKA and cGMP-PKG, regulate LTCC gating in two opposing ways: the cAMP-PKA pathway potentiates while the cGMP-PKG cascade inhibits LTCCs. Despite this, no attempts have been made to answer three key questions related to the two Cav1 isoforms expressed in MCCs (Cav1.2 and Cav1.3): (i) how much are the two Cav1 channels basally modulated by PKA and PKG?, (ii) to what extent can Cav1.2 and Cav1.3 be further regulated by PKA or PKG activation?, and (iii) are the effects of both kinases cumulative when simultaneously active? Here, by comparing the size of L-type currents of wild-type (WT; Cav1.2 + Cav1.3) and Cav1.3 -/- KO (Cav1.2) MCCs, we provide new evidence that both PKA and PKG pathways affect Cav1.2 and Cav1.3 to the same extent either under basal conditions or induced stimulation. Inhibition of PKA by H89 (5 μm) reduced the L-type current in WT and KO MCCs by ∼60%, while inhibition of PKG by KT 5823 (1 μm) increased by ∼40% the same current in both cell types. Given that Cav1.2 and Cav1.3 carry the same quantity of Ca 2+ currents, this suggests equal sensitivity of Cav1.2 and Cav1.3 to the two basal modulatory pathways. Maximal stimulation of cAMP-PKA by forskolin (100 μm) and activation of cGMP-PKG by pCPT-cGMP (1 mm) uncovered a ∼25% increase of L-type currents in the first case and ∼65% inhibition in the second case in both WT and KO MCCs, suggesting equal sensitivity of Cav1.2 and Cav1.3 during maximal PKA or PKG stimulation. The effects of PKA and PKG were cumulative and most evident when one pathway was activated and the other was inhibited. The two extreme combinations (PKA activation-PKG inhibition vs. PKG activation-PKA inhibition) varied the size of L-type currents by one order of magnitude (from 180% to 18% of control size). Taken together our data suggest that: (i) Cav1.2 and Cav1.3 are equally sensitive to PKA and PKG action under both basal conditions and maximal stimulation, and (ii) PKA and PKG act independently on both Cav1.2 and Cav1.3, producing cumulative effects when opposingly activated. These extreme Cav1 channel modulations may occur either during high-frequency sympathetic stimulation to sustain prolonged catecholamine release (maximal L-type current) or following activation of the NO-cGMP-PKG signalling pathway (minimal L-type current) to limit the steady release of catecholamines. © 2012 The Authors. The Journal of Physiology © 2012 The Physiological Society.


Mouse and rat chromaffin cells (MCCs, RCCs) fire spontaneously at rest and their activity is mainly supported by the two L-type Ca(2+) channels expressed in these cells (Ca(v)1.2 and Ca(v)1.3). Using Ca(v)1.3(-/-) KO MCCs we have shown that Ca(v)1.3 possess all the prerequisites for carrying subthreshold currents that sustain low frequency cell firing near resting (0.5 to 2 Hz at -50 mV): low-threshold and steep voltage dependence of activation, slow and incomplete inactivation during pulses of several hundreds of milliseconds. Ca(v)1.2 contributes also to pacemaking MCCs and possibly even Na(+) channels may participate in the firing of a small percentage of cells. We now show that at potentials near resting (-50 mV), Ca(v)1.3 carries equal amounts of Ca(2+) current to Ca(v)1.2 but activates at 9 mV more negative potentials. MCCs express only TTX-sensitive Na(v)1 channels that activate at 24 mV more positive potentials than Ca(v)1.3 and are fully inactivating. Their blockade prevents the firing only in a small percentage of cells (13%). This suggests that the order of importance with regard to pacemaking MCCs is: Ca(v)1.3, Ca(v)1.2 and Na(v)1. The above conclusions, however, rely on the proper use of DHPs, whose blocking potency is strongly holding potential dependent. We also show that small increases of KCl concentration steadily depolarize the MCCs causing abnormally increased firing frequencies, lowered and broadened AP waveforms and an increased facility of switching "non-firing" into "firing" cells that may lead to erroneous conclusions about the role of Ca(v)1.3 and Ca(v)1.2 as pacemaker channels in MCCs.


Deganello F.,CNR Institute of Nanostructured Materials | Tummino M.L.,CNR Institute of Nanostructured Materials | Tummino M.L.,University of Turin | Calabrese C.,CNR Institute of Nanostructured Materials | And 7 more authors.
New Journal of Chemistry | Year: 2015

For the first time, sustainable LaFeO3 powders were prepared from soluble bio-based substances (SBO) extracted from urban wastes. For the preparation of the perovskite-type powders, a modified solution combustion synthesis route was used, where SBO have the triple role of fuel, complexant and microstructural templates. A careful examination of the LaFeO3 powders, using complementary characterization techniques, evidenced their peculiar microstructural, morphological, textural and photocatalytic properties. Preliminary photodegradation tests of a phenol-based wastewater pollutant and photobleaching of a model dye were performed on the waste-derived and reference LaFeO3 powders; the obtained results encourage further studies on the application of these materials as heterogeneous catalysts for wastewater treatment. Moreover, a meaningful amount of entrapped matter was evidenced in the powders, which is responsible for most of their peculiar properties. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015.


Fiori F.,Marche Polytechnic University | Lussana D.,Nis Center | Riontino G.,Nis Center
Journal of Alloys and Compounds | Year: 2010

A quantitative description of the Mg-rare earth EV31 alloy during the first stages of the precipitation sequence using in situ small-angle X-ray scattering (SAXS) is presented. In situ evolutions of the size, volume fraction and number density of precipitates formed at 150 °C and 200 °C were obtained. A kinetic mechanism suggests that the precursor nanoparticles are nucleated at the beginning of the artificial ageing and, at 200 °C, these particles grow mainly by accretion of the solute from the matrix without further nucleation. The particles grow within two regimes: (i) at the beginning of ageing, the growth is associated with solute diffusion with an apparent activation energies of 0.78 eV (diffusion assisted by vacancies); (ii) further growth is associated with solute diffusion with an apparent activation energies of 1.16 eV (bare solute diffusion). After about 2 h at 200 °C, corresponding to the condition of maximum hardness for this alloy, the present results indicate a volume fraction of about 1.5% occupied by particles with an average Guinier radius of 2 nm. The evolution of the volume fraction at 150 °C, studied for a similar time interval, is weaker than the one found at 200 °C. © 2009 Elsevier B.V. All rights reserved.


Comunanza V.,NIS Center | Carbone E.,NIS Center | Marcantoni A.,NIS Center | Sher E.,Eli Lilly and Company | Ursu D.,Eli Lilly and Company
Pflugers Archiv European Journal of Physiology | Year: 2011

We studied the inhibitory effects of transient receptor potential vanilloid-1 (TRPV1) activation by capsaicin on low-voltage-activated (LVA, T-type) Ca 2+ channel and high-voltage-activated (HVA; L, N, P/Q, R) currents in rat DRG sensory neurons, as a potential mechanism underlying capsaicin-induced analgesia. T-type and HVA currents were elicited in whole-cell clamped DRG neurons using ramp commands applied before and after 30-s exposures to 1 μM capsaicin. T-type currents were estimated at the first peak of the I-V characteristics and HVA at the second peak, occurring at more positive potentials. Small and medium-sized DRG neurons responded to capsaicin producing transient inward currents of variable amplitudes, mainly carried by Ca 2+. In those cells responding to capsaicin with a large Ca 2+ influx (59% of the total), a marked inhibition of both T-type and HVA Ca 2+ currents was observed. The percentage of T-type and HVA channel inhibition was prevented by replacing Ca 2+ with Ba 2+ during capsaicin application or applying high doses of intracellular BAPTA (20 mM), suggesting that TRPV1-mediated inhibition of T-type and HVA channels is Ca 2+-dependent and likely confined to membrane nano-microdomains. Our data are consistent with the idea that TRPV1-induced analgesia may derive from indirect inhibition of both T-type and HVA channels which, in turn, would reduce the threshold of nociceptive signals generation (T-type channel inhibition) and nociceptive synaptic transmission (HVA-channels inhibition). © 2011 Springer-Verlag.


Mouse chromaffin cells (MCCs) generate action potential (AP) firing that regulates the Ca


PubMed | NIS Center
Type: Journal Article | Journal: Pflugers Archiv : European journal of physiology | Year: 2011

We studied the inhibitory effects of transient receptor potential vanilloid-1 (TRPV1) activation by capsaicin on low-voltage-activated (LVA, T-type) Ca(2+) channel and high-voltage-activated (HVA; L, N, P/Q, R) currents in rat DRG sensory neurons, as a potential mechanism underlying capsaicin-induced analgesia. T-type and HVA currents were elicited in whole-cell clamped DRG neurons using ramp commands applied before and after 30-s exposures to 1M capsaicin. T-type currents were estimated at the first peak of the I-V characteristics and HVA at the second peak, occurring at more positive potentials. Small and medium-sized DRG neurons responded to capsaicin producing transient inward currents of variable amplitudes, mainly carried by Ca(2+). In those cells responding to capsaicin with a large Ca(2+) influx (59% of the total), a marked inhibition of both T-type and HVA Ca(2+) currents was observed. The percentage of T-type and HVA channel inhibition was prevented by replacing Ca(2+) with Ba(2+) during capsaicin application or applying high doses of intracellular BAPTA (20mM), suggesting that TRPV1-mediated inhibition of T-type and HVA channels is Ca(2+)-dependent and likely confined to membrane nano-microdomains. Our data are consistent with the idea that TRPV1-induced analgesia may derive from indirect inhibition of both T-type and HVA channels which, in turn, would reduce the threshold of nociceptive signals generation (T-type channel inhibition) and nociceptive synaptic transmission (HVA-channels inhibition).

Loading NIS Center collaborators
Loading NIS Center collaborators