Yuste R, Denk W
Biological Computation Research Department, AT&T Bell Laboratories, Murray Hill, New Jersey 07974, USA.
Nature. 1995 Jun 22;375(6533):682-4. doi: 10.1038/375682a0.
Most excitatory synaptic connections occur on dendritic spines. Calcium imaging experiments have suggested that spines constitute individual calcium compartments, but recent results have challenged this idea. Using two-photon microscopy to image fluorescence with high resolution in strongly scattering tissue, we measured calcium dynamics in spines from CA1 pyramidal neurons in slices of rat hippocampus. Subthreshold synaptic stimulation and spontaneous synaptic events produced calcium accumulations that were localized to isolated spines, showed stochastic failure, and were abolished by postsynaptic blockers. Single somatic spikes induced fast-peaking calcium accumulation in spines throughout the cell. Pairing of spikes with synaptic stimulation was frequently cooperative, that is, it resulted in supralinear calcium accumulations. We conclude: (1) calcium channels exist in spine heads; (2) action potentials invade the spines; (3) spines are individual calcium compartments; and (4) spines can individually detect the temporal coincidence of pre- and postsynaptic activity, and thus serve as basic functional units of neuronal integration.
大多数兴奋性突触连接发生在树突棘上。钙成像实验表明，树突棘构成独立的钙区室，但最近的研究结果对这一观点提出了挑战。我们利用双光子显微镜在强散射组织中进行高分辨率荧光成像，测量了大鼠海马切片中CA1锥体神经元树突棘内的钙动力学。阈下突触刺激和自发突触事件产生的钙积累局限于单个孤立的树突棘，呈现随机失效，并被突触后阻滞剂消除。单个体细胞动作电位可在整个细胞的树突棘中诱导快速峰值钙积累。动作电位与突触刺激配对时通常具有协同作用，即会导致超线性钙积累。我们得出以下结论：（1）树突棘头部存在钙通道；（2）动作电位可侵入树突棘；（3）树突棘是独立的钙区室；（4）树突棘能够单独检测突触前和突触后活动的时间一致性，因此可作为神经元整合的基本功能单位。
