Wiegand H, Lohmann H, Chandra S V
Arch Toxicol. 1986 Apr;58(4):265-70. doi: 10.1007/BF00297118.
Endplate potentials (EPP's) and miniature endplate potentials (MEPP's) were recorded from neuromuscular junctions of the mouse phrenic nerve-diaphragm preparation, blocked by high Mg++ (12 X 10(-3) mol/l)-Ringer. Superfusion of the preparations with Mg++-Ringer solutions containing thallium acetate (5 X 10(-4) mol/l Tlac) decreased phasic transmitter release as judged by EPP amplitudes as well as average quantal content, until total synaptic blockade (within about 300 min) occurred. Simultaneously MEPP amplitudes remained unchanged, whereas the frequency of MEPP's increased. When EPP amplitudes and/or quantal content were reduced by 50% (usually within about 180 min), superfusion with Mg++-Ringer solution without Tlac did not restore phasic transmitter release. However, the increase in spontaneous transmitter release was reversible, as MEPP frequencies returned to normal values. 4-Aminopyridine (5 X 10(-4) mol/l 4-AP) as added to the bath solution in the state of 50%-reduced phasic release temporarily restored EPP amplitudes and average quantal content, whereas MEPP amplitudes remained unchanged. It is concluded that thallium irreversibly blocks phasic transmitter release, whereas spontaneous transmitter release is reversibly enhanced.
在高镁（12×10⁻³mol/L）-林格液阻断的小鼠膈神经-膈肌标本的神经肌肉接头处记录终板电位（EPP）和微小终板电位（MEPP）。用含醋酸铊（5×10⁻⁴mol/L Tlac）的镁-林格液灌流标本，根据EPP幅度和平均量子含量判断，相性递质释放减少，直至完全突触阻断（约300分钟内）发生。同时，MEPP幅度保持不变，而MEPP的频率增加。当EPP幅度和/或量子含量降低50%（通常在约180分钟内）时，用不含Tlac的镁-林格液灌流不能恢复相性递质释放。然而，自发递质释放的增加是可逆的，因为MEPP频率恢复到正常值。在相性释放减少50%的状态下，向浴液中加入4-氨基吡啶（5×10⁻⁴mol/L 4-AP）可暂时恢复EPP幅度和平均量子含量，而MEPP幅度保持不变。结论是铊不可逆地阻断相性递质释放，而自发递质释放则可逆性增强。
