CALCIUM PERMEABILITY OF NEURONAL NICOTINIC ACETYLCHOLINE-RECEPTOR CHANNELS IN PC12 CELLS

被引:84
作者
SANDS, SB
BARISH, ME
机构
[1] UNIV CALIF IRVINE, COLL MED, DEPT PHYSIOL & BIOPHYS, IRVINE, CA 92717 USA
[2] CITY HOPE NATL MED CTR, BECKMAN RES INT, DIV NEUROSCI, DUARTE, CA 91010 USA
关键词
NEURONAL NICOTINIC ACETYLCHOLINE RECEPTOR; CA PERMEABILITY;
D O I
10.1016/0006-8993(91)91211-I
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
The conductance properties of neuronal nicotinic acetylcholine receptors (neuronal nAChR channels) in PC12 cells were studied using single channel and whole cell gigaohm seal voltage clamp techniques. Acetylcholine receptor agonists were applied using external pipettes. Neuronal nAChR channels were selective for monovalent cations, and were impermeable to anions. Based on measurements of shifts in reversal potential with changes in external Na and K ion concentrations and evaluation of the GHK constant field relation, P K/P(Na) was 1.45 (ignoring Ca permeability). P Ca/P(K) was 1.75 based on the shift in reversal potential seen when raising the external Ca concentration from 2 to 50 mM (holding the external Na ion concentration constant), and determining the best fit to the extended GHK constant field relation using ionic activities. This value is larger than that determined for the muscle-type nAChR channel. Evaluation of the extended GHK current equations using these permeability coefficients indicated that at subthreshold voltage approximately 5% of total current through neuronal nAChR channels will be carried by Ca ions. Thus, these channels may be important mediators of activity-dependent Ca influx in the nervous system.
引用
收藏
页码:38 / 42
页数:5
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