外侧缰核内谷氨酸能神经元介导吗啡戒断后痛觉过敏的机制研究

Addiction and pain are in close association and interact with each other tightly, while researches focused on the mechanism of the relationship between them are scarce. The hyperalgesia induced by opioid withdrawal is a typical manifestion of addiction induced pain, its mechanism is neither unclear. Lateral habenula(LHb) is an important nerve center for the modulation of addiction and pain. Neurons in the LHb are activated abundantly after opiate withdrawal or painful stimulation. We have also observed that lesioning LHb, targeting down-regulating the expression of vesicular glutamate transporter 2 in LHb or selectively inhibiting the activity of glutamatergic projections from LHb to ventrolateral periaqueductal gray(vlPAG) attenuated hyperalgesia induced by morphine withdrawal significantly, while the hyperalgesia reoccured after blocking GABA receptor in the vlPAG, indicating that glutamatergic neurons in the LHb may take part in regulating hyperalgesia induced by morphine withdrawal and its mechanism may be related with GABA in the vlPAG. The present program, by using a combination of optogenetics techniques, morphology techniques, electrophysiology techniques and molecular biology techniques, intends to identify the role of LHb in hyperalgesia after opiate withdrawal and to explore the possible mechanism: glumatergic neurons in the LHb are activated after opiate withdrawal, then inhibit glutamatergic neurons in the vlPAG via activating GABAergic intermediate neurons, finally attenuate descending inhibition of pain and result in hyperalgesia.

成瘾与疼痛联系密切且互相影响，然而以往鲜有将二者结合起来的机制研究。阿片戒断后痛觉过敏是成瘾诱发疼痛的典型表现，其机制不明确。外侧缰核（LHb）是成瘾及疼痛的关键中枢，吗啡戒断或疼痛时其内神经元大量激活。我们前期观察到，毁损LHb、靶向下调LHb内囊泡膜谷氨酸转运体2表达或抑制LHb向中脑导水管周围灰质腹外侧亚核（vlPAG）的谷氨酸能投射的活动均显著缓解小鼠吗啡戒断后痛觉过敏，而激活vlPAG内GABA受体后痛觉过敏再次增强，提示LHb中谷氨酸能神经元参与调控吗啡戒断后痛觉过敏，其机制可能与vlPAG内GABA活动有关。本项目拟利用光遗传学技术，结合电生理、形态及分子生物学技术明确LHb在吗啡戒断后痛觉过敏中的作用，并探索可能的机制：吗啡戒断后LHb内谷氨酸能神经元兴奋，后通过兴奋GABA能中间神经元间接抑制vlPAG内谷氨酸能神经元，导致vlPAG对痛觉下行抑制减弱、痛觉过敏产生。

成瘾与疼痛是两种联系密切且互相影响的临床疾病。阿片类药物戒断后痛觉过敏是成瘾导致疼痛的典型表现，该现象在临床十分常见且危害严重，但其机制不明确。外侧缰核（LHb）是近年来神经科学领域的一个热点，其内部的谷氨酸能神经元已经被证明参与调控抑郁、焦虑、疼痛及成瘾等多种神经功能障碍。 但LHb是否参与介导阿片类药物戒断后痛觉过敏及其机制尚不明确。.本项目关注LHb内谷氨酸能神经元的作用，探索其可能在吗啡戒断后痛觉过敏中的作用机制。利用了形态学、分子生物及电生理技术等多种技术研究，证实了LHb内谷氨酸能神经元→vlPAG内GABA能神经元→vlPAG内谷氨酸能神经元这一间接投射通路的存在。发现了吗啡戒断后痛觉过敏条件下该通路上游LHb内谷氨酸能神经元的高度激活。并验证了抑制LHb 内谷氨酸能神经元活动后吗啡戒断后痛觉过敏减弱。通过以上研究提出了阿片类药物过敏后痛觉过敏的可能机制：吗啡戒断后LHb内谷氨酸能神经元兴奋，通过兴奋GABA能中间神经元间接抑制vlPAG内谷氨酸能神经元，导致vlPAG对痛觉下行抑制减弱，痛觉过敏产生。这为阿片戒断后痛觉过敏的治疗发现了新靶点。此外，本项目还发现脑干外侧网状核内大量谷氨酸能神经元共表达囊泡膜谷氨酸转运体1及2，这类神经元参与向小脑投射并在大鼠上肢精细活动调控中发挥关键作用。.