Molecular Pain：吗啡对内外侧痛觉通路信息传递的影响

吗啡及其他阿片类激动剂因其强大的镇痛作用被广泛应用于临床上对疼痛的治疗。然而，人类对于阿片类药物在脊髓水平之上的镇痛机制的认识却很有限。

心理所心理健康院重点实验室罗非研究员、王锦琰副研究员及其团队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，研究吗啡在疼痛的内外侧通路对伤害性感觉加工的调节作用。其中，SI和VPL位于疼痛加工的外侧通路，处理疼痛的感觉信息，而ACC和MD位于疼痛加工的内侧通路，处理疼痛的情绪信息。结果表明，大鼠腹腔注射5mg/kg的吗啡能够显著降低伤害性热辐射刺激所引发的四个脑区神经元活动的改变，包括降低神经元对热辐射刺激的反应幅度、反应比例、反应持续时间，以及削弱皮层和丘脑神经元群对伤害性刺激和非伤害性刺激的分辨能力。另外，吗啡还能够抑制由疼痛引起的内、外侧通路之间以及皮层-丘脑之间的信息流动，该效应能够被阿片受体拮抗剂纳洛酮所阻断。上述研究结果表明，吗啡通过抑制疼痛的情绪和感觉维度起到镇痛作用，进而在皮层和丘脑水平阐明了吗啡的镇痛机制。该研究对于吗啡镇痛机制的基础研究起到了推动作用，为临床治疗提供了有力的理论依据。（生物谷Bioon.com）

生物谷推荐原始出处：

Molecular Pain 2009, 5:60doi:10.1186/1744-8069-5-60

Morphine modulation of pain processing in medial and lateral pain pathways

Jin-Yan Wang* 1 , Jin Huang* 2 , Jing-Yu Chang3 , Donald J Woodward3  and Fei Luo1

1Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Science, Beijing, China
2Neuroscience Research Institute, Peking University, Beijing, China
3Neuroscience Research Institute of North Carolina, Winston-Salem, NC, USA

Background
Despite the wide-spread use of morphine and related opioid agonists in clinic and their powerful analgesic effects, our understanding of the neural mechanisms underlying opioid analgesia at supraspinal levels is quite limited. The present study was designed to investigate the modulative effect of morphine on nociceptive processing in the medial and lateral pain pathways using a multiple single-unit recording technique. Pain evoked 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 eight-wire microelectrode arrays in awake rats.

Results
The results showed that the noxious heat evoked responses of single neurons in all of the four areas were depressed after systemic injection of 5 mg/kg morphine. The depressive effects of morphine included (i) decreasing the neuronal response magnitude; (ii) reducing the fraction of responding neurons, and (iii) shortening the response duration. In addition, the capability of cortical and thalamic neural ensembles to discriminate noxious from innocuous stimuli was decreased by morphine within both pain pathways. Meanwhile, morphine suppressed the pain-evoked changes in the information flow from medial to lateral pathway and from cortex to thalamus. These effects were completely blocked by pre-treatment with the opiate receptor antagonist naloxone.

Conclusion
These results suggest that morphine exerts analgesic effects through suppressing both sensory and affective dimensions of pain.