Karunanithi S, Lavidis N A, Bennett M R
Department of Physiology, University of Sydney, NSW, Australia.
Eur J Pharmacol. 1994 Aug 11;261(1-2):17-24. doi: 10.1016/0014-2999(94)90295-x.
A study was undertaken to ascertain why in the mouse vas deferens excitatory junction potentials facilitate whereas contractions depress during low frequency stimulation. In a set of contraction studies, where a conditioning stimulus was followed 2 s later by a test stimulus, depression in the first phase of contraction was observed only at high stimulus strengths when many nerves are activated leading to a large secretion. Low stimulus strengths did not produce depression, suggesting that the autoinhibitory effect due to released noradrenaline is absent. At supramaximal stimulus strengths short, low frequency (0.1-0.5 Hz) trains gave varying degrees of depression of the first phase at each stimulus frequency. This depression was reversed by yohimbine (10 microM), indicating that the level of autoinhibition depends on the total amount of noradrenaline secreted. In the absence of autoinhibition, facilitation could be predicted in terms of the residual Ca2+ hypothesis.
开展了一项研究，以确定为何在低频刺激期间，小鼠输精管的兴奋性接头电位表现为易化，而收缩却受到抑制。在一组收缩研究中，条件刺激后2秒施加测试刺激，仅在高刺激强度下，即激活许多神经导致大量分泌时，才观察到收缩第一阶段的抑制。低刺激强度未产生抑制，这表明不存在因去甲肾上腺素释放所致的自身抑制作用。在超最大刺激强度下，短时间的低频（0.1 - 0.5 Hz）串刺激在每个刺激频率下均使第一阶段出现不同程度的抑制。育亨宾（10 microM）可逆转这种抑制，这表明自身抑制水平取决于分泌的去甲肾上腺素总量。在不存在自身抑制的情况下，可根据残余钙假说预测易化现象。
