Penn R D, Loewenstein W R
Science. 1966 Jan 7;151(3706):88-9. doi: 10.1126/science.151.3706.88.
Calcium ion participates in maintaining electrical connections between the nerve cells of Retzius (Hirudo medicinalis). The conductance across the junction between these cells decreases with decreasing concentration of free, extracellular Ca(++) At a certain level of Ca(++) withdrawal from the cell system, junctional conductance reaches a critical low point at which the cells become functionally disconnected: the nerve impulses which are normally discharged in synchrony by the cells become asynchronous. These effects of Ca(++) on junctional connection are irreversible, in contrast to those on nonjunctional surface membrane permeability.
钙离子参与维持蛭类（医蛭）中Retzius神经细胞之间的电连接。这些细胞之间连接部位的电导随着细胞外游离Ca(++)浓度的降低而减小。当从细胞系统中去除一定水平的Ca(++)时，连接部位的电导达到一个临界低点，此时细胞在功能上断开连接：正常情况下由这些细胞同步发放的神经冲动变得不同步。与Ca(++)对非连接部位表面膜通透性的影响相反，Ca(++)对连接部位连接的这些影响是不可逆的。
