Hong S J, Lnenicka G A
Department of Biological Sciences, University at Albany, SUNY 12222, USA.
J Neurosci. 1995 May;15(5 Pt 1):3539-47. doi: 10.1523/JNEUROSCI.15-05-03539.1995.
The effect of increased impulse activity upon voltage-dependent Ca2+ currents was studied in the cell body of a crayfish phasic motoneuron using two-electrode voltage-clamp technique. Increased electrical activity in this relatively inactive motoneuron produces a short-term and long-term reduction in the voltage-dependent Ca2+ current. Both forms of activity-dependent reduction in Ca2+ current are Ca2+ dependent. The short-term reduction in Ca2+ current appears to involve the Ca(2+)-dependent inactivation of Ca2+ channels, previously described in a variety of neurons. The long-term reduction in Ca2+ current is produced by prolonged Ca2+ influx and persists for days: in vivo stimulation of the phasic motor axon at 5 Hz for 1 hr results in a 30% reduction in Ca2+ current density, which persists for at least 3 d. Both the short-term and long-term reductions in Ca2+ current appear to result from changes in a single type of high-voltage-activated (HVA) Ca2+ channel. Inhibition of protein synthesis attenuates the long-term reduction in Ca2+ current and has no effect upon the short-term Ca2+ current reduction. During the long-term reduction in Ca2+ current, it appears that Ca2+ channels located distant to the site of Ca2+ influx are affected. The relationship of these results to a previously described Ca(2+)-dependent reduction in transmitter release is discussed.
采用双电极电压钳技术，在小龙虾相位性运动神经元的胞体中研究了冲动活动增加对电压依赖性Ca2+电流的影响。在这个相对不活跃的运动神经元中，电活动增加会导致电压依赖性Ca2+电流出现短期和长期的降低。这两种形式的Ca2+电流活动依赖性降低均依赖于Ca2+。Ca2+电流的短期降低似乎涉及Ca2+通道的Ca(2+)依赖性失活，这在多种神经元中已有描述。Ca2+电流的长期降低是由Ca2+的持续内流引起的，并持续数天：在体内以5Hz的频率刺激相位性运动轴突1小时，会导致Ca2+电流密度降低30%，且至少持续3天。Ca2+电流的短期和长期降低似乎都是由单一类型的高电压激活（HVA）Ca2+通道的变化引起的。蛋白质合成的抑制会减弱Ca2+电流的长期降低，而对Ca2+电流的短期降低没有影响。在Ca2+电流的长期降低过程中，似乎远离Ca2+内流部位的Ca2+通道受到了影响。文中讨论了这些结果与先前描述的Ca(2+)依赖性递质释放减少之间的关系。
