We have studied the contribution of N-type voltage-dependent Ca2+ channels to both norepinephrine and epinephrine secretion from bovine chromaffin cells induced by high K+ or nicotine using ω-conotoxin GVIA, a selective blocker of N-type voltage-dependent Ca2+ channels. We found that high K+ (75 mM) induced catecholamine secretion was not affected by exposure of bovine chromaffin cells to ω-conotoxin GVIA (1 μM). However, nicotine-induced both norepinephrine and epinephrine secretion were similarly blocked (about 25%) by ω-conotoxin GVIA (1 μM). This effect could be explained by a potent (about 80%) and reversible blockade of the inward current induced by nicotine receptor activation in bovine chromaffin cells. The results indicate that besides the blockade of N-type voltage-dependent channels, ω-conotoxin GVIA is a potent and reversible blocker of the nicotinic receptor-induced currents in chromaffin cells.
Bibliographical noteFunding Information:
4,8 y---3r---vtinic receptor activation in other neurosecretory systems. -L--This work has been supported, in part, by grants from 15 Fundacion Salud 2000, Direccicin General de Investiga-Fig. 2. Effect of o-conotoxin GVIA on nicotine-induced currents. In- cion Cientifica y Tecnica, grant #PM92-0112 and the (10pM)with an interval of 15 min as described in the text. During theward current induced by three consecutive applications of nicotine European Economic Community, grant #SCl*-CT91-second application of nicotine w-conotoxin GVIA (1 PM) was present, 0709. R.G. is supported by a University of Alicante fel-The figure represent a typical experiment that was repeated four times lowship; J.M.F. by a CAM fellowship and V.I. by a Gen-with similar results. eralitat Valenciana fellowship.
- Chromaffin cells
- Nicotine-induced catecholamine secretion
- Nicotinic receptor-induced currents