Barman S M, McCaffrey T V, Wurster R D
Am J Physiol. 1976 Apr;230(4):1095-1100. doi: 10.1152/ajplegacy.1976.230.4.1095.
Anesthetized, vagotomized, and paralyzed cats were used to study the relationship between changes in blood pressure and T2 preganglionic nerve activity elicited by stimulation of descending spinal sympathoexcitatory pathways. While low-frequency stimulation (1-10 Hz) resulted in a depressor response, an attenuation of sympathetic nerve evoked discharges was noted after the second pulse of twin-pulse stimulations with 1,000- to 100-ms intervals between stimuli (corresponding to 1-10 Hz). High-frequency stimulation (greater than 10 Hz) resulted in a pressor response, while preganglionic nerve-evoked discharges were enhanced during twin-pulse stimulations with intervals between stimuli less than 50 ms (corresponding to greater than 20 Hz). These data suggest that the depressor response during low-frequency stimulation may be explained by impulses occurring during the silent period of the previous response. During this time the preganglionic neuron is inexcitable and spontaneous activity is abolished; therefore, the blood pressure falls. High-frequency stimulation may result in a pressor response by increasing the number of preganglionic neurons that are activated. This may be due to a process of temporal summation, with initial stimuli bringing cells closer to their threshold for firing and additional stimuli close in time causing these neurons to discharge.
使用麻醉、切断迷走神经并使其麻痹的猫来研究刺激脊髓下行交感兴奋通路所引发的血压变化与T2节前神经活动之间的关系。低频刺激（1 - 10赫兹）会导致降压反应，而在双脉冲刺激的第二个脉冲后，交感神经诱发放电会减弱，刺激间隔为1000至100毫秒（对应1 - 10赫兹）。高频刺激（大于10赫兹）会导致升压反应，而在刺激间隔小于50毫秒（对应大于20赫兹）的双脉冲刺激期间，节前神经诱发放电会增强。这些数据表明，低频刺激期间的降压反应可能是由前一次反应的静息期出现的冲动所解释。在此期间，节前神经元无法兴奋且自发活动被消除；因此，血压下降。高频刺激可能通过增加被激活的节前神经元数量而导致升压反应。这可能是由于时间总和的过程，初始刺激使细胞更接近其放电阈值，而时间上接近的额外刺激导致这些神经元放电。
