McAllen R M, Trevaks D
Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Melbourne, Australia.
Acta Physiol Scand. 2003 Mar;177(3):219-25. doi: 10.1046/j.1365-201X.2003.01072.x.
The idea that, like somatic motor neurones, sympathetic pre-ganglionic neurones are engaged to fire in a pre-determined recruitment order, was investigated in chloralose-anaesthetized cats.
Ongoing pre-ganglionic spike activity was recorded from fine filaments of otherwise intact thoracic white rami, while post-ganglionic activity was recorded from the whole inferior cardiac nerve (ICN). Spikes of individual pre-ganglionic fibres were extracted from few-fibre recordings by spike shape analysis. Presumed cardiac pre-ganglionic fibres were further selected by the spike-triggered average of ICN activity, which showed a clear peak when triggered by their spikes.
To test whether particular pre-ganglionic neurones were recruited to fire in a set time sequence, the spontaneous spike trains of fibres in the same white ramus were compared by cross correlation. In all 24 cases the cross correlograms showed a central peak (width 163 +/- 15 ms), indicating that the two neurones tended to fire together. In 23 of the 24 cases that peak spanned the zero point on the time axis, showing that each neurone could fire either first or second. To test whether pre-ganglionic neurones were recruited in a set order with respect to burst amplitude, the firing of individual pre-ganglionic neurones was compared with the strength of the corresponding post-ganglionic burst discharge, on a heartbeat-by-heartbeat basis. Pre-ganglionic neurone firing was probabilistic: each neurone fired with only a minority of post-ganglionic bursts. Firing probability increased linearly with burst amplitude (30 of 30 cases). The slope of the relation varied between units, but its intercept was always close to the origin (zero pre-ganglionic firing probability at zero post-ganglionic burst size).
The data indicate that, at least under these conditions, sympathetic pre-ganglionic neurones follow no set recruitment sequence in either their firing times or with respect to the strength of the autonomic motor output.
在水合氯醛麻醉的猫身上研究这样一种观点，即与躯体运动神经元一样，交感神经节前神经元按预先确定的募集顺序放电。
从原本完整的胸段白交通支的细丝记录持续的节前尖峰活动，而从整个心下神经（ICN）记录节后活动。通过尖峰形状分析从少纤维记录中提取单个节前纤维的尖峰。通过ICN活动的尖峰触发平均值进一步选择假定的心脏节前纤维，当由它们的尖峰触发时，该平均值显示出一个明显的峰值。
为了测试特定的节前神经元是否按设定的时间顺序被募集放电，通过互相关比较同一白交通支中纤维的自发尖峰序列。在所有24例中，互相关图显示一个中心峰值（宽度163±15毫秒），表明这两个神经元倾向于一起放电。在24例中的23例中，该峰值跨越时间轴上的零点，表明每个神经元既可以先放电也可以后放电。为了测试节前神经元是否按照爆发幅度的设定顺序被募集，在逐个心跳的基础上，将单个节前神经元的放电与相应节后爆发放电的强度进行比较。节前神经元放电是概率性的：每个神经元仅在少数节后爆发时放电。放电概率随爆发幅度呈线性增加（30例中的30例）。单位之间关系的斜率有所不同，但其截距总是接近原点（节后爆发大小为零时节前放电概率为零）。
数据表明，至少在这些条件下，交感神经节前神经元在其放电时间或自主运动输出强度方面没有遵循设定的募集顺序。
