Chow R H, Klingauf J, Heinemann C, Zucker R S, Neher E
Max Planck Institute for Biophysical Chemistry, Department of Membrane Biophysics, Goettingen, Germany.
Neuron. 1996 Feb;16(2):369-76. doi: 10.1016/s0896-6273(00)80054-9.
Transmitter release from chromaffin cells differs from that in synapses in that it persists for a longer time after Ca2+ entry has stopped. This prolonged secretion is not due to a delay between vesicle fusion and transmitter release, nor to slow detection of released substance: step increases in capacitance due to single vesicle fusion precede the release detected by amperometry by only a few milliseconds. The persistence of secretion after a depolarization is reduced by addition of mobile calcium buffer. This suggests that most of the delay is due to diffusion of Ca2+ between channels and release sites, implying that Ca2+ channels and secretory vesicles are not colocalized in chromaffin cells, in contrast to presynaptic active zones.
嗜铬细胞释放递质与突触释放递质不同，在于在Ca2+进入停止后，它持续的时间更长。这种延长的分泌并非由于囊泡融合与递质释放之间存在延迟，也不是由于对释放物质的检测缓慢：单个囊泡融合导致的电容阶跃增加仅比安培检测法检测到的释放提前几毫秒。去极化后分泌的持续性会因添加可移动钙缓冲剂而降低。这表明大部分延迟是由于Ca2+在通道与释放位点之间的扩散，这意味着与突触前活动区不同，Ca2+通道和分泌囊泡在嗜铬细胞中并非共定位。
