Watson A H, Bazzaz A A
School of Biosciences, University of Wales Cardiff, Cardiff CF10 3US, United Kingdom.
J Comp Neurol. 2001 May 7;433(3):335-48. doi: 10.1002/cne.1143.
The object of this study was to analyze the synaptic interactions of identified muscle spindle afferent axon terminals in the spinal cord of the rat. Group 1a muscle afferents supplying the gastrocnemius muscle were impaled with microelectrodes in the dorsal white matter of the spinal cord and stained by intracellular injection with Neurobiotin. Postembedding immunogold techniques were used to reveal GABA- and glycine-like immunoreactivity in boutons presynaptic to afferent terminals in the ventral horn and the deep layers of the dorsal horn. Serial-section reconstruction was used to reveal the distribution of synaptic contacts of different types on the afferent terminals. The majority of afferent boutons received axoaxonic and made axodendritic or axosomatic synaptic contacts. In the ventral horn, 91% of boutons presynaptic to the afferent terminals were immunoreactive for GABA alone and 9% were immunoreactive for both GABA and glycine. The mean number of axo-axonic contacts received per terminal was 2.7, and the mean number of synaptic contacts at which the terminal was the presynaptic element was 1.4. In the deep layers of the dorsal horn, 58% of boutons presynaptic to afferent terminals were immunoreactive for GABA alone, 31% were immunoreactive for GABA and glycine, and 11% for glycine alone. The mean number of axoaxonic contacts received per afferent terminal in this region was 1.6 and the mean number of synaptic contacts at which the terminal was the presynaptic element was 0.86. This clearly establishes the principle that activity in 1a afferents is modulated by several neurochemically distinct populations of presynaptic neuron.
本研究的目的是分析大鼠脊髓中已确定的肌梭传入轴突终末的突触相互作用。供应腓肠肌的Ⅰa类肌传入纤维在脊髓背侧白质中用微电极刺入，并通过细胞内注射神经生物素进行染色。采用包埋后免疫金技术揭示腹角和背角深层传入终末突触前小体中的GABA和甘氨酸样免疫反应性。连续切片重建用于揭示不同类型突触接触在传入终末上的分布。大多数传入小体接受轴-轴突触联系，并形成轴-树突或轴-体突触接触。在腹角，传入终末突触前的小体中，91%仅对GABA有免疫反应，9%对GABA和甘氨酸均有免疫反应。每个终末接受的轴-轴突触联系的平均数为2.7，终末作为突触前成分的突触接触平均数为1.4。在背角深层，传入终末突触前的小体中，58%仅对GABA有免疫反应，31%对GABA和甘氨酸有免疫反应，11%仅对甘氨酸有免疫反应。该区域每个传入终末接受的轴-轴突触联系的平均数为1.6，终末作为突触前成分的突触接触平均数为0.86。这清楚地确立了一个原则，即Ⅰa类传入纤维的活动受几种神经化学性质不同的突触前神经元群体的调节。
