岛叶到伏隔核通路对小鼠痛觉的影响

Effects of insula to nucleus accumbens pathway on pain sensation in mice

目的探究投向伏隔核的岛叶神经元对小鼠痛觉的影响。方法使用雄性78周C57BL/6小鼠,在伏隔核注射逆向示踪包含Cre重组酶片段的腺相关病毒,在岛叶皮质分别注射Cre重组酶依赖的破伤风轻链改造TetTox,光敏感通道蛋白NpHR或光敏感通道蛋白ChR2的腺相关病毒。病毒表达28 d后,在岛叶皮质埋置光纤,埋置光纤2周后,进行光遗传学实验。通过行为学实验检测机械痛和辣椒素引起的急性疼痛。对机械痛,采用Von Frey细丝,使用up and down的方法进行痛阈检测小鼠的缩足阈值;对辣椒素引起的急性疼痛,使用辣椒素足底注射进行急性疼痛造模,观察并统计小鼠的舔爪时间及抬爪时间。结果沉默投向伏隔核的岛叶神经元使小鼠缩足阈值上升(P=0.01);光抑制岛叶到伏隔核通路使小鼠缩足阈值上升(P=0.02),急性疼痛下的舔爪时间(P=0.04)和抬爪时间降低(P=0.02),与沉默岛叶神经元对痛觉行为的影响一致;光激活投向伏隔核的岛叶神经元引起缩足阈值下降(P=0.0008),而舔爪时间(P=0.95)和抬爪时间(P=0.46)并没有减少。结论岛叶到伏隔核通路参与疼痛的传导和调控,抑制投向伏隔核的岛叶神经元使小鼠痛阈上升,激活岛叶投射到伏隔核的神经元使小鼠缩足阈值下降。

Objective To investigate the effect of insular neurons subset in nucleus accumbens on pain perception in mice.Methods The adeno-associated virus(AAV)vectors expressing the Reteo-Cre recombinase(Retro-Cre)were injected into the nucleus accumbens of C57BL/6J male mice,and the AAV vectors with Cre-inducible expression of Tetanus light chain modification of TetTox/light sensitive channel protein NpHR or light sensitive channel protein ChR2 were injected into the insula.Twenty-eight days after virus expression,optical fibers were embedded in the insula cortex,and two weeks later,optogenetics was performed.Behavioral tests were performed to detect mechanical pain and acute pain induced by capsaicin.The up-and-down method was used to detect the paw withdrawal threshold with Von Frey hairs.Capsaicin were injected into the sole of the foot induced acute pain model,the paw licking time and paw total lifting time were observed and counted.Results Silenced IC-NAc increased paw withdrawal threshold in mice(P=0.01).Optogenetics-inhibited IC-NAc increased the paw withdrawal threshold(P=0.02),in acute pain model,paw licking time(P=0.04)and paw total lifting time(P=0.02)increased.It was consistent with the effect of silencing insular neurons on nociceptive behavior.Optogenetics-activated IC-NAC showed decreased paw withdrawal threshold(P=0.0008),but no difference in paw licking time(P=0.95)and total lifting time(P=0.46).Conclusion The inhibition of insular neurons projecting to nucleus accumbens can increase pain threshold in mice,and the activation of insular neurons projecting to nucleus accumbens can decrease paw withdrawal threshold in mice.Insular to nucleus accumbens pathway may be involved in pain transduction and regulation in mice.