Distinct temporal profiles of activity-dependent calcium increase in pyramidal neurons of the rat visual cortex

作     者：Kato, N Tanaka, T Yamamoto, K Isomura, Y 

作者机构：Kyoto Univ Grad Sch Med Dept Integrat Brain Sci Kyoto 6068501 Japan 

出 版 物：《JOURNAL OF PHYSIOLOGY-LONDON》 (生理学杂志)

年 卷 期：1999年第519卷第2期

页      面：467-479页

核心收录：

学科分类：0710[理学-生物学] 1001[医学-基础医学(可授医学、理学学位)] 07[理学] 071003[理学-生理学] 

主　　题：苯胺化合物 钙/代谢 钙信号/药物作用 钙信号/生理学 电刺激 兴奋性突触后电位/药物作用 兴奋性突触后电位/生理学 荧光染料 Fura-2 神经元可塑性/药物作用 神经元可塑性/生理学 膜片钳术 光度测定法 锥体细胞/药物作用 锥体细胞/代谢 锥体细胞/生理学 大鼠 Wistar 时间因素 视皮质/细胞学 视皮质/代谢 视皮质/生理学 呫吨类 动物 大鼠 

摘      要：1. Using fluo-3-based fluorometry, we studied variation in depolarization-induced calcium increases in the proximal dendrites or soma of pyramidal neurons in layer II/III of the rat visual cortex. 2. Depolarization for all durations tested (0.1-2 s;0.5 nA) evoked a train of action potentials and a small increase in calcium signal (mean 26%) which peaked within I s of the onset of depolarization. With depolarization for longer than Is, this small increase was often followed by a larger increase (73%). This later phase of calcium increase occurred without sudden changes in action potential firing. 3. Application of ryanodine, which suppresses intracellular calcium release, abolished the second phase without affecting the early phase in a use-dependent manner. Meanwhile, no major changes were observed in the pattern of action potential firing. 4. In calcium-free medium, both the early and late phases were almost undetectable, although action potential firing was still evoked by injection of depolarizing currents. Since the late phase depended on intracellular calcium release, this effect of calcium-free medium on the late phase is likely to be indirect through an influence on the early phase. 5. This two-phase profile was observed with somatic depolarization or with antidromic action potentials induced by tetanization. Neocortical pyramidal neurons can thus recruit calcium from different sources, even without chemical sensitization, generating temporally diverse profiles of intracellular calcium signal in response to action potential firing. 6. Such variety in the mechanisms of calcium increase may be relevant to the role of calcium as a versatile second messenger for various types of synaptic plasticity.