Fiala J C, Feinberg M, Popov V, Harris K M
Division of Neuroscience in the Department of Neurology, Children's Hospital, Boston Massachusetts, USA.
J Neurosci. 1998 Nov 1;18(21):8900-11. doi: 10.1523/JNEUROSCI.18-21-08900.1998.
To determine the role of dendritic filopodia in the genesis of excitatory synaptic contacts and dendritic spines in hippocampal area CA1, serial section electron microscopy and three-dimensional analysis of 16 volumes of neuropil from nine male rat pups, aged postnatal day 1 (P1) through P12, were performed. The analysis revealed that numerous dendritic filopodia formed asymmetric synaptic contacts with axons and with filopodia extending from axons, especially during the first postnatal week. At P1, 22 +/- 5.5% of synapses occurred on dendritic filopodia, with 19 +/- 5.9% on filopodia at P4, 20 +/- 8.0% at P6, decreasing to 7.2 +/- 4.7% at P12 (p < 0.02). Synapses were found at the base and along the entire length of filopodia, with many filopodia exhibiting multiple synaptic contacts. In all, 162 completely traceable dendritic filopodia received 255 asymmetric synaptic contacts. These synapses were found at all parts of filopodia with equal frequency, usually occurring on fusiform swellings of the diameter. Most synaptic contacts (53 +/- 11%) occurred directly on dendritic shafts during the first postnatal week. A smaller but still substantial portion (32 +/- 12%) of synapses were on shafts at P12 (p < 0.036). There was a highly significant (p < 0.0002) increase in the proportion of dendritic spine synapses with age, rising from just 4.9 +/- 4.3% at P1 to 37 +/- 14% at P12. The concurrence of primarily shaft and filopodial synapses in the first postnatal week suggests that filopodia recruit shaft synapses that later give rise to spines through a process of outgrowth.
为确定树突丝状伪足在海马CA1区兴奋性突触联系和树突棘形成过程中的作用，对9只出生后1天（P1）至12天的雄性幼鼠的16块神经毡进行了连续切片电子显微镜检查和三维分析。分析显示，许多树突丝状伪足与轴突以及从轴突伸出的丝状伪足形成不对称突触联系，尤其是在出生后的第一周。在P1时，22±5.5%的突触出现在树突丝状伪足上，P4时为19±5.9%，P6时为20±8.0%，到P12时降至7.2±4.7%（p<0.02）。在丝状伪足的基部和整个长度上都发现了突触，许多丝状伪足呈现多个突触联系。总共162个可完全追踪的树突丝状伪足接受了255个不对称突触联系。这些突触在丝状伪足的各个部位出现的频率相等，通常出现在直径的梭形膨大部分。在出生后的第一周，大多数突触联系（53±11%）直接出现在树突干上。在P12时，较小但仍相当一部分（32±12%）的突触位于树突干上（p<0.036）。随着年龄增长，树突棘突触的比例显著增加（p<0.0002），从P1时的仅4.9±4.3%上升到P12时的37±14%。出生后第一周主要是树突干和丝状伪足突触同时出现，这表明丝状伪足招募树突干突触，这些突触随后通过生长过程产生树突棘。
