CROSS-CORRELATION ASSESSMENT OF SYNAPTIC STRENGTH OF SINGLE IA FIBER-CONNECTIONS WITH TRICEPS SURAE MOTONEURONS IN CATS
CROSS-CORRELATION ASSESSMENT OF SYNAPTIC STRENGTH OF SINGLE IA FIBER-CONNECTIONS WITH TRICEPS SURAE MOTONEURONS IN CATS
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DOI：
10.1113/jphysiol.1987.sp016692
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发表时间：
1987-09-01
影响因子：
5.5
通讯作者：
MATSUMURA, M
中科院分区：
文献类型：
--
作者：
COPE, TC;FETZ, EE;MATSUMURA, M
1.在巴比妥酸麻醉的猫上，研究了由单个Ia纤维产生的兴奋性突触后电位（eps）与小腿三头肌运动神经元产生的交叉相关图之间的关系。首先记录eps，使用肌肉拉伸诱发的单个Ia纤维的放电来编译运动神经元膜电位的尖峰触发平均值。随后，Ia纤维动作电位与细胞内注射电流诱导的相同运动神经元的节律性放电交叉相关。2.初级相关图峰值有统计学意义的49个单一的Ia纤维运动神经元连接的31。相关图的累积总和用于确定峰的开始和持续时间。对于涉及超过2000个触发尖峰的20个病例，13个显示出显著的相关图峰值。对于这13个，平均百分比增加（m.p.i.）在运动神经元放电概率中，定义为相关图峰值高于基线的平均高度，范围为29 - 138%。k值（最大高度除以基线）范围为2.1至5.2。峰值持续时间为1.8 ~ 3.2ms，其余7例Ia e. p. s. p. s无明显相关图峰值（P > 0.05）。3. m.p.i.在运动神经元放电概率和e. p. s. p.振幅（n = 13）中，平均斜率为0.30%/μ V。k值与e. p. s. p.振幅的相关性更弱（r = 0.67; P < 0.01）。与e.p.s.p振幅最强相关的相关图参数（r = 0.80）是相关图峰面积（每个兴奋性突触后电位高于基线的尖峰数量）。E. p. s. p.上升率与m.p.i.放电概率（r = 0.28）和峰面积（r = 0.36）。4.主要相关图峰值的形状可以在很大程度上由与e. p. s. p.导数成比例的函数来解释（在时间对准之后）。从相关图峰值中减去与e. p. s. p.导数成比例的函数，留下可忽略的余数或余数项，其持续时间短于e. p. s. p. 5。为了研究重复性放电过程中运动神经元阈值附近发生的单纤维Ia e. p. s. p. s的特性，选择性地使用在膜电位去极化斜坡末端附近发生的Ia尖峰对e. p. s. p. s进行平均。这些“斜坡e. p. s. p. s”往往是有点小（约。8%），比静息状态下运动神经元在相同连接处产生的“静息eps”多。斜坡上升时间通常比静止上升时间短或长，但在一致的方向上没有差异。相关图峰面积和m.p.i.在射击概率方面，斜升式比静止式性能更好。6.相关图峰值的性质与（a）内在运动神经元性质（包括基强度电流和传导速度）、（B）Ia纤维-运动神经元连接类型（同源或异源）或（c）脊髓状况（完整或急性横断）无明显相关。7.它的结论是交叉相关图提供了一个直接的测量突触强度在单一的Ia纤维运动神经元连接。这些相关图证实，单一Ia纤维提高运动神经元放电概率的幅度tidue的基础epsps的比例。
1. The relation between excitatory post-synaptic potentials (e.p.s.p.s) produced by single Ia fibres and the resultant cross-correlograms in triceps surae motoneurones was investigated in barbiturate-anaesthetized cats. The e.p.s.p.s were documented first, using the discharge of single Ia fibres evoked by muscle stretch to compile spike-triggered averages of motoneurone membrane potential. Subsequently, Ia fibre action potentials were cross-correlated with rhythmic discharge of the same motoneurones induced by intracellular injection of current. 2. Primary correlogram peaks were statistically significant for thirty-one of forty-nine single Ia fibre-motoneurone connections. Cumulative sums of correlograms were used to identify the onset and duration of peaks. For twenty cases involving more than 2000 trigger spikes, thirteen showed significant correlogram peaks. For these thirteen, the mean percentage increase (m.p.i.) in motoneurone firing probability, defined as the mean height of the correlogram peak above base line, ranged from 29 to 138%. The k values (maximum height divided by base line) ranged from 2.1 to 5.2. Peak duration varied from 1.8 to 3.2 ms. In the remaining seven cases the Ia e.p.s.p.s produced no significant correlogram peak (i.e. P > 0.05). 3. A significant positive relationship (r = 0.76; P < 0.005) was found between m.p.i. in motoneurone firing probability and e.p.s.p. amplitude (n = 13), with a mean slope of 0.30%/.mu.V. The k values were more weakly related to e.p.s.p. amplitude (r = 0.67; P < 0.01). The correlogram parameter most strongly related to e.p.s.p ampilitude (r = 0.80) was correlogram peak area (number of spikes above base line per excitatory post-synaptic potential). E.p.s.p. rate of rise was not significantly related (P > 0.10) to either m.p.i. in firing probability (r = 0.28) or peak area (r = 0.36). 4. The shapes of the primary correlogram peaks could be accounted for largely by a function proportional to the e.p.s.p. derivative (after temporal alignment). Subtracting a function proportional to the e.p.s.p. derivative from the correlogram peak left either a negligible remainder or a remainder term whose duration was shorter than the e.p.s.p. 5. To investigate properties of single-fibre Ia e.p.s.p.s occurring near motoneurone threshold during repetitive firing, e.p.s.p.s were selectively averaged using Ia spikes occurring near the end of the depolarizing ramp in membrane potential. These ''ramp e.p.s.p.s'' tended to be somewhat smaller (by ca. 8%) than the ''rest e.p.s.p.s'' produced at the same connections with the motoneurone at rest. Ramp-e.p.s.p. rise times were often substantially shorter or longer than rest-e.p.s.p. rise times, but did not differ in a consistent direction. Correlogram peak area and m.p.i. in firing probability were better releated to ramp- than to rest-e.p.s.p. properties. 6. Properties of the correlogram peaks were not obviously related to (a) intrinsic motoneurone properties, including rheobase current and conduction velocity, (b) the type of Ia fibre-motoneurone connection, homonymous or heteronymous, or (c) the condition of the spinal cord, intact or acutely transected. 7. It is concluded that cross-correlograms provide a direct measure of synaptic strength at single Ia fibre-motoneurone connections. These correlograms confirm that single Ia fibres raise motoneurone firing probability in proportion to the amplitude tidue to the underlying e.p.s.p.s.