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To investigate the effects of pentobarbital anesthesia on nociceptive processing in the medial and lateral pain pathways.
Laser stimulation was employed to evoke nociceptive responses in rats under awake or anesthetic conditions. Pain-related neuronal activities were simultaneously recorded from the primary somatosensory cortex (SI), ventral posterolateral thalamus (VPL), anterior cingulate cortex (ACC), and medial dorsal thalamus (MD) with 4 eight-wire microelectrode arrays.
Compared with the awake state, pentobarbital anesthesia significantly suppressed the neural activities induced by noxious laser stimulation. Meanwhile, the pain-evoked changes in the neuronal correlations between cortex and thalamus were suppressed in both medial and lateral pain pathways. In addition, the spontaneous firing rates in all the 4 areas were altered (including inhibition and excitation) under the condition of anesthesia.
The nociceptive processing in the brain can be dramatically changed by anesthesia, which indicates that there are considerable differences in the brain activities between awake and anesthetized states. It is better to employ awake animals for recording neural activity when investigating the sensory coding mechanisms, especially pain coding, in order to obtain data that precisely reflect the physiological state.
利用清醒动物神经细胞群单位放电多通道同步记录技术, 在大鼠的初级躯体感觉皮层(SI)、 丘脑腹后外侧核(VPL)、 前扣带皮层(ACC)以及丘脑背内侧核(MD)埋置电极, 给予对侧足底伤害性激光刺激, 观察大鼠清醒状态下以及戊巴比妥钠麻醉状态下由激光刺激引发的各脑区神经活动的变化。
与清醒状态相比, 戊巴比妥钠麻醉显著降低了伤害性激光刺激所引发的四个脑区神经元活动的增强, 同时也抑制了由疼痛引起的内、 外侧通路上脑区之间的同步电活动。 另外, 各脑区的自发放电频率也因麻醉而发生显著改变, 包括抑制和增强两种情况。
麻醉能显著改变疼痛相关的神经活动, 表明大脑活动在麻醉与清醒状态下有着很大差别。 该结果提示, 在研究感觉神经编码尤其是痛觉编码时, 最好使用清醒动物记录神经活动, 以获得能真正反映生理状态的实验数据。
These authors contributed equally to this work.