Desensitization shortens the high-quantal-content endplate current time course in frog muscle with intact cholinesterase

被引:18
作者
Giniatullin, RA
Talantova, M
Vyskocil, F
机构
[1] ACAD SCI CZECH REPUBL,INST PHYSIOL,CR-14220 PRAGUE 4,CZECH REPUBLIC
[2] CHARLES UNIV,FAC SCI,DEPT ANIM PHYSIOL & DEV BIOL,PRAGUE,CZECH REPUBLIC
[3] KAZAN MED UNIV,DEPT PHYSIOL,KAZAN,RUSSIA
来源
JOURNAL OF PHYSIOLOGY-LONDON | 1997年 / 502卷 / 03期
关键词
D O I
10.1111/j.1469-7793.1997.641bj.x
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
1. The desensitization induced by bath-applied carbachol or acetylcholine (ACh) and potentiated by proadifen (SKF 525A) was studied in the frog sartorius with intact synaptic acetylcholinesterase (AChE). 2. The reduction in the density and number of postsynaptic receptors produced by desensitization lowered the amplitude of the endplate currents (EPCs) and shortened the EPC decay when the quantal content (m) of the EPC was about 170 and when multiple release of quanta at single active zones was highly probable. The shortening of high-quantal-content EPCs persisted for at least 15 min after the wash-out of agonists, at a time when the amplitude had recovered fully. 3. The decay times of the low-quantal-content EPCs recorded from preparations pretreated with 5 mM Mg2+ (m approximate to 70) and single-quantum miniature endplate currents (MEPCs) were not affected by carbachol, ACh or proadifen. 4. The desensitization of ACh receptors potentiated by proadifen, prevented completely the 6- to 8-fold prolongation of EPC which was induced by neostigmine inhibition of synaptic AChE. 5. It is assumed that high-quantal-content EPCs increase the incidence of multiple quanta release at single active zones and the probability of repetitive binding of ACh molecules which leads to EPC prolongation. The shortening which persists after complete recovery of the amplitude during wash-out of the exogenous agonist is probably due to 'trapping' of ACh molecules onto rapidly desensitized receptors and the reduced density of functional AChRs during the quantum action.
引用
收藏
页码:641 / 648
页数:8
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