Noradrenergic inhibition and voltage-dependent facilitation of omega-conotoxin-sensitive Ca channels in insulin-secreting RINm5F cells. |
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| Authors: | G Aicardi A Pollo E Sher E Carbone |
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| Affiliation: | Department of Anatomy and Human Physiology, Torino, Italy. |
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| Abstract: | We found that, besides dihydropyridine-sensitive Ca channels, insulin-secreting RINm5F cells also contain a minority (15-25%) of omega-conotoxin (omega-CgTx)-sensitive channels that show a high-affinity binding to [125I] omega-CgTx (Kd 51 pM). Noradrenaline (NA, 10 microM) slows down Ca-channel activation in these cells and produces a sizeable reduction of Ca currents that is relieved by strong pre-conditioning depolarizations (facilitation). The action of NA is mimicked by intracellular application of GTP-gamma-S and is prevented by pertussis toxin (PTX) or by cell pre-incubation with omega-CgTx. This suggests specific noradrenergic inhibition of omega-CgTx-sensitive Ca channels that is modulated by membrane potentials and PTX-sensitive G-protein activation. |
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