經(jīng)典的疼痛學(xué)研究認為,，痛覺的上傳過程中存在兩條平行通路,，分別負責(zé)疼痛的感覺和情緒信息傳遞。其中,，外側(cè)通路負責(zé)傳遞疼痛的感覺信息,，包括強度、位置和性質(zhì)等,，內(nèi)側(cè)通路則傳遞疼痛的情緒相關(guān)信息,。盡管近年來有研究提示，內(nèi)側(cè)疼痛通路可能也具有編碼疼痛刺激強度的能力,，然而對于其編碼特征與外側(cè)通路有何差別卻知之甚少,。
激光刺激在內(nèi)外側(cè)痛覺通路誘發(fā)的神經(jīng)反應(yīng)
為此,，中科院心理健康重點實驗室羅非研究員、王錦琰副研究員及其團隊利用清醒動物神經(jīng)細胞群單位放電多通道同步記錄技術(shù),，在大鼠的初級軀體感覺皮層(SI),、丘腦腹后外側(cè)核(VPL)、前扣帶皮層(ACC)以及丘腦背內(nèi)側(cè)核(MD)埋置電極,，研究疼痛的內(nèi)外側(cè)通路對傷害刺激強度的編碼特征,。其中SI和VPL位于疼痛加工的外側(cè)通路，而ACC和MD位于疼痛加工的內(nèi)側(cè)通路,。研究人員在給予大鼠后肢足底六個遞增強度的傷害性激光刺激同時,，監(jiān)測這四個腦區(qū)，隨后分析其神經(jīng)元個數(shù),、放電頻率以及整體放電數(shù)這三種編碼模式,。
研究結(jié)果表明：在所有記錄到的四個腦區(qū)都可以觀察到傷害性激光刺激激活的雙峰反應(yīng)；激光刺激強度與有反應(yīng)神經(jīng)元數(shù),、放電頻率以及群放電數(shù)之間分別存在顯著相關(guān),，而群體放電數(shù)這種編碼方式相比較另外兩種編碼方式，與激光刺激強度的相關(guān)性更為顯著,；更重要的是,，通過判別分析表明，兩條通路對傷害性刺激強度的的編碼能力相當(dāng),，且兩者共同作用時,，編碼能力最強。
這一研究證明,，內(nèi)側(cè)通路不僅能夠編碼傷害刺激強度,，且其編碼特征與外側(cè)通路神經(jīng)元相類似，兩者共同貢獻了對強度的編碼,，同時表明群放電數(shù)可能是一種最優(yōu)的疼痛強度編碼方式,。
本研究已發(fā)表于《分子疼痛》（Moleculer Pain）。(生物谷 Bioon.com)
doi:10.1186/1744-8069-7-64
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Ensemble encoding of nociceptive stimulus intensity in the rat medial and lateral pain systems
Yang Zhang, Ning Wang, Jin-Yan Wang, Jing-Yu Chang, Donald J Woodward and Fei Luo
Background The ability to encode noxious stimulus intensity is essential for the neural processing of pain perception. It is well accepted that the intensity information is transmitted within both sensory and affective pathways. However, it remains unclear what the encoding patterns are in the thalamocortical brain regions, and whether the dual pain systems share similar responsibility in intensity coding. Results Multichannel single-unit recordings were used to investigate the activity of individual neurons and neuronal ensembles in the rat brain following the application of noxious laser stimuli of increasing intensity to the hindpaw. Four brain regions were monitored, including two within the lateral sensory pain pathway, namely, the ventral posterior lateral thalamic nuclei and the primary somatosensory cortex, and two in the medial pathway, namely, the medial dorsal thalamic nuclei and the anterior cingulate cortex. Neuron number, firing rate, and ensemble spike count codings were examined in this study. Our results showed that the noxious laser stimulation evoked double-peak responses in all recorded brain regions. Significant correlations were found between the laser intensity and the number of responsive neurons, the firing rates, as well as the mass spike counts (MSCs). MSC coding was generally more efficient than the other two methods. Moreover, the coding capacities of neurons in the two pathways were comparable. Conclusion This study demonstrated the collective contribution of medial and lateral pathway neurons to the noxious intensity coding. Additionally, we
