Lemos J R, Nowycky M C
Neurobiology Group, Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.
Neuron. 1989 May;2(5):1419-26. doi: 10.1016/0896-6273(89)90187-6.
The properties of the Ca2+ channels mediating transmitter release in vertebrate neurons have not yet been described with voltage-clamp techniques. Several types of voltage-dependent Ca2+ channels are known to exist on neuronal somata, but the small size and inaccessibility of most vertebrate nerve endings have precluded direct characterization of the presynaptic channels. However, large nerve endings, which release the peptides oxytocin and vasopressin in a Ca2(+)-dependent manner, can be dissociated from the rat neurohypophysis. Using both single-channel and whole-cell patch-clamp techniques, we have characterized two types of Ca2+ channels that coexist in these terminals. One is a large-conductance, high-threshold, dihydropyridine-sensitive channel that contributes a slowly inactivating current. The second is a smaller conductance channel, which is also activated at high thresholds, but underlies a rapidly inactivating, dihydropyridine-insensitive current. Both types of Ca2+ channels may participate in the peptide release process.
介导脊椎动物神经元递质释放的Ca2+通道特性尚未通过电压钳技术进行描述。已知神经元胞体上存在几种类型的电压依赖性Ca2+通道，但大多数脊椎动物神经末梢体积小且难以接近，这使得无法直接对突触前通道进行特性描述。然而，以Ca2(+)-依赖方式释放催产素和加压素肽的大神经末梢可以从大鼠神经垂体中分离出来。使用单通道和全细胞膜片钳技术，我们已经对这些终末中共存的两种类型的Ca2+通道进行了特性描述。一种是大电导、高阈值、对二氢吡啶敏感的通道，它产生一个缓慢失活的电流。第二种是较小电导的通道，它也在高阈值时被激活，但作为一个快速失活、对二氢吡啶不敏感的电流的基础。这两种类型的Ca2+通道都可能参与肽释放过程。
