中脑腹侧被盖区至岛叶的多巴胺能神经投射通路参与慢性痛及负性情绪调控的机制

Both ventral tegmental area (VTA) and insular cortex (IC) are involved in the regulations of pain and its related negative emotions. Morphologically, the VTA send projections to the IC. However, the functional connetions between these two regions and the underlying mechanisms remain unclear. Our previous work demonstrated that the VTA could send dopaminergic (DAergic) projections to the IC. Moreover, the electrophysiological activities of VTA-IC projecting neurons were decreased under neuropathic pain (NP) conditions in mice. By utilizing optogenetic method to specifically manipulate DAergic VTA-IC projecting fibers, we found that the pain threshold as well as negative emotions, such as anxiety and depression of NP mice could be alleviated. Consequently, taking advantage of tyrosine hydroxylase (TH)-Cre recombinase transgenetic mice, we try to specifically investigate the regulatory effects of DAergic VTA-IC projections on the IC neuronal activity, as well as the chronic pain and related negative emotions changes in behavioral mice, by integrating neurobiological techniques. Our proposed work will shed light on the the underlying mechanisms of DA’s regulatory effects on the cortex, and point out novel avenues for clinical therapies for chronic pain and its related negative emotions.

中脑腹侧被盖区(VTA)和岛叶(IC)均是疼痛及其伴随负性情绪调控的重要脑区。形态学上，VTA可以向IC发出纤维投射，但功能上的联系和机制尚不清楚。我们前期的研究工作表明，VTA内的多巴胺(DA)能神经元向IC发出投射。神经病理性痛状态下，小鼠VTA-IC投射神经元电生理活性明显降低。通过光遗传学技术特异性地激活VTA-IC的DA能投射纤维，可以缓解动物的痛行为和焦虑、抑郁等负性情绪。本项目将在此基础上，以酪氨酸羟化酶(TH)-Cre小鼠为实验对象，通过综合应用先进的神经科学实验方法，研究VTA发出的DA能投射纤维对IC内神经元活性的调节效应和机制，探讨该通路对慢性痛及其伴随的负性情绪发生发展的影响。该研究将为DA在皮层的作用机制提供重要的实验依据，也有益于临床慢性痛及其相关负性情绪的治疗和药物研发。

中脑腹侧被盖区（VTA）和岛叶（IC）均是疼痛及其伴随负性情绪调控的重要脑区。VTA可以向IC发出纤维投射，但功能上的联系和机制尚不清楚。我们采用SNI建立小鼠神经病理性痛模型。应用束路追踪结合原位杂交及免疫荧光多重染色技术观察到，VTA-IC投射神经元主要为多巴胺（DA）能，少部分为抑制性GABA神经元；在神经病理性痛状态下，VTA-IC投射神经元激活。IC内来自VTA的投射纤维既能够与CaMKII阳性兴奋性神经元，也能够与GAD67阳性抑制性神经元形成密切接触，而抑制性神经元同时主要表达D1R。接着采用Western Blot检测观察到，SNI状态下小鼠IC内DA明显降低，D1R表达明显下降，而D2R表达却明显升高。接着我们利用电生理膜片钳技术钳制VTA-IC投射神经元，记录并观察到，SNI状态下，其神经元自发性兴奋性突触后电流（sEPSC）的频率和幅值明显减低，提示突触前和突触后其兴奋性均明显降低，同时其自发放电、固有兴奋性也明显降低，说明VTA-IC投射神经元电生理活性明显降低。最后通过光遗传学技术，将携带兴奋性光敏蛋白的病毒注射入TH-Cre小鼠的VTA，用蓝光刺激IC，特异性地激活VTA-IC的DA能投射神经纤维，我们观察到SNI小鼠的痛行为和焦虑、抑郁等负性情绪得到明显缓解。本研究证实VTA-IC神经通路作为一条重要的痛调控通路在神经病理性痛状态下被抑制，特异性激活该通路能够显著改善动物痛行为和其伴随的负性情绪，为DA在皮层的作用机制提供重要的实验依据，也有益于临床慢性痛及其相关负性情绪的治疗和药物研发。