CALCIUM-DEPENDENCE OF QUANTAL SECRETION FROM VISUALIZED SYMPATHETIC-NERVE VARICOSITIES ON THE MOUSE VAS-DEFERENS

被引:23
作者
MACLEOD, GT [1 ]
LAVIDIS, NA [1 ]
BENNETT, MR [1 ]
机构
[1] UNIV SYDNEY,DEPT PHYSIOL,NEUROBIOL LAB,SYDNEY,NSW 2006,AUSTRALIA
来源
JOURNAL OF PHYSIOLOGY-LONDON | 1994年 / 480卷
关键词
D O I
10.1113/jphysiol.1994.sp020340
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
1. The effects of calcium on the secretion of quanta recorded from single varicosities on the surface of the mouse vas deferens has been determined. 2. If recordings were made from two adjacent varicosities and the [Ca2+](0) increased from a low value (1mM), then the increase in the mean quantal content of the endplate potential (($) over bar m(e)) was almost entirely due to an increase in the binomial probability for secretion (p(e)). At higher [Ca2+], there was an increasing tendency for the binomial parameter (n(e)) to increase from 1 to 2. When n(e) increased there was very little change in p(e), indicating that the new release site recruited from the other varicosity has a relatively low probability for secretion. 3. If recordings were restricted to single varicosities and the [Ca2+](0) increased in the range from 1 to 4 mM then the increases in ($) over bar m(e) were almost always due to an increase in p(e). The gradient relating the log of ($) over bar m(e) to the log of [Ca2+](0) for [Ca2+](0) of 1.0-1.5 mM was in the range 3.2-5.4 (mean 4.2). 4. Test impulses gave a similar proportional increase in ($) over bar m(e) following a conditioning impulse at all varicosities from which recordings were made. 5. Facilitation of ($) over bar m(e) declined exponentially with an increase in the test-conditioning interval from 0.5 to 4 s. The time constant for this decline was about 6 s. 6. The results indicate that single release sites show a similar fourth power dependency on[Ca2+](0) and facilitate to about the same degree following a conditioning impulse.
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页码:61 / 70
页数:10
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