Spinal nociceptive neurons are well known to undergo a process of long-term potentiation (LTP) following conditioning by high-frequency sciatic nerve stimulation (HFS) at intensities recruiting C-fibers. However, little if any information exists as to whether such HFS conditioning that produces spinal LTP affects sensory transmission at supraspinal levels. The present study explored this possibility. Conventional extracellular recording methods were used to examine the consequences of HFS versus sham HFS conditioning on individual wide-dynamic range thalamic neurons located in the ventro-postero-lateral (VPL) nucleus in isoflurane-anesthetized rats. Following HFS, the ongoing firing rate and stimulus-evoked (brush, pinch, sciatic nerve) responses were markedly enhanced as were responses to juxtacellular, microiontophoretic applications of glutamate. These HFS-induced enhancements lasted throughout the recording period. Sham stimuli had no effect on VPL neuron excitability. Cortical electroencephalographic (EEG) wave activities were also measured around HFS in conjunction with VPL neuron recordings. The cortical EEG pattern under baseline conditions consisted of recurring short duration bursts of high-amplitude slow waves followed by longer periods of flat EEG. Following HFS, the EEG shifted to a continuous large-amplitude, slow-wave pattern within the 0.5-8.0 Hz bandwidth lasting throughout the recording period. Sham HFS did not alter EEG activity. Sciatic nerve conditioning at A-δ fiber strength, known to reverse spinal LTP, did not alter enhanced neuronal excitability or the EEG slow-wave pattern induced by HFS. These data support the concept that HFS conditioning of the sciatic nerve, which leads to spinal LTP, is associated with distinct, long-lasting changes in the excitability of neurons comprising thalamocortical networks.

译文

众所周知,脊髓伤害感受神经元经过高频坐骨神经刺激(HFS)调节C纤维强度后会经历长期增强(LTP)过程。但是,关于这种产生脊柱LTP的HFS调理是否会影响脊髓上水平的感觉传递,几乎没有任何信息。本研究探讨了这种可能性。常规的细胞外记录方法用于检查HFS与假HFS调节对异氟烷麻醉大鼠腹侧后外侧(VPL)核中单个宽动态范围丘脑神经元的影响。 HFS后,持续的射击频率和刺激诱发的(刷,捏,坐骨神经)反应显着增强,对谷氨酸的近细胞,微离子电渗疗法的反应也明显增强。这些由HFS引起的增强在整个记录期间一直持续。假刺激对VPL神经元兴奋性没有影响。还测量了HFS周围的皮质脑电图(EEG)波活动以及VPL神经元记录。基线条件下的皮质脑电图模式由高振幅慢波的反复短时突发和随后较长时间的平坦脑电图组成。在进行HFS之后,EEG在整个记录周期内转移到0.5-8.0 Hz带宽内的连续大振幅慢波模式。 Sham HFS并未改变脑电图活动。已知可以逆转脊柱LTP的A-δ纤维强度的坐骨神经调节不会改变增强的神经元兴奋性或HFS诱发的EEG慢波模式。这些数据支持这样的概念,即坐骨神经的HFS调节导致脊柱LTP,与包括丘脑皮质网络的神经元的兴奋性发生明显且持久的变化有关。

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