中脑腹侧被盖区多巴胺能神经元短暂激活未能诱发小鼠自身给糖行为的重建

Transient activation of dopaminergic neurons in ventral tegmental area of midbrain fails to induce reinstatement of sucrose self-administration behavior in mice

目的研究脑内奖赏系统中脑腹侧被盖区(VTA)多巴胺(DA)能神经元对灯光线索诱发小鼠自身给糖行为重建的调控作用。方法以转基因DAT-Cre小鼠为研究对象,通过病毒转染的方式,将光敏感通道蛋白特异性表达在小鼠VTA的DA能神经元上。采用10%蔗糖水训练注射过携带光敏感通道蛋白重组腺相关病毒的小鼠建立自身给糖行为,然后进行首次消退训练,达到首次消退期稳定阶段(连续3 d小鼠有效鼻触次数<10%形成期稳定操作值)后,进行线索点燃测试。随后,小鼠进行第2次消退,达到第2次消退期稳定阶段,采用频率20 Hz、脉冲时长15 ms的激光连续100次集中刺激VTA的DA能神经元。最后进行第3次消退,达到第3次消退期稳定阶段,采用频率80 Hz、脉冲时长15 ms的激光连续100次集中刺激VTA的DA能神经元。结果在相关灯光线索刺激下,小鼠出现蔗糖行为重建,表现为有效鼻触次数较首次消退期稳定阶段有效鼻触次数(首次消退期最后3 d的有效鼻触次数平均值)显著升高(P<0.01),提示蔗糖相关灯光线索可显著诱发小鼠觅糖行为重建,实验模型建立成功。20 Hz 15 ms或80 Hz 15 ms的激光刺激小鼠VTA能特异性激活多巴胺能神经元,与第2次消退期稳定阶段或者第3次消退期稳定阶段的有效鼻触次数相比,上述激光刺激对小鼠有效鼻触次数无显著影响。结论在自身给糖小鼠模型中,VTA脑区单一类型DA能神经元的短暂激活不足以诱发小鼠觅糖行为重建。

OBJECTIVE To explore the regulation of dopaminergic neurons in the ventral tegmental area(VTA)on the reinstatement during sucrose-induced self-administration in mice.METHODS A sucrose self-administration behavior model was established in DAT-Cre mice.By means of viral transfection,light sensitive channel protein was specifically expressed in dopaminergic neurons in the VTA of the brain of mice.Mice injected with rAAV-EF1α-DIO-hChR2-mCherry-WPRE-pA were trained with 10%sucrose water to establish their sucrose self-administration behavior.Then,the first extinction training was performed,and cue priming was performed after the stable stage of the first extinction period was reached(the number of active pokes in mice for 3 consecutive days<10%stable operation value at the formation stage).Then the mice underwent the second extinction,and reached the stable stage.The dopaminergic neurons of the VTA were continuously stimulated by laser with a frequency of 20 Hz and pulse duration of 15 ms for 100 times.Finally,the third extinction was performed until the stable stage was reached.The dopaminergic neurons of the VTA were continuously stimulated by laser with a frequency of 80 Hz and pulse duration of 15 ms for 100 times.RESULTS Under the stimulation of rele⁃vant light cues,sucrose behavior reinstatement was observed in mice,which showed that the number of active pokes was significantly increased compared with the first extinction(the mean number of active pokes in the last 3 days of the first extinction period)(P<0.01),suggesting that sucrose related cues could significantly induce the reinstatement of sucrose-seeking behavior in mice.Laser stimulation at 20 Hz 15 ms or 80 Hz 15 ms specifically activated dopaminergic neurons in the VTA.Compared with the number of active pokes in the stable stage of the second or third extinction stage,the above laser stimulation had no significant effect on the number of active pokes in mice.CONCLUSION In the sucrose self-administration model,the transient activation of a single type of dopaminergic neurons in the VTA is insufficient to induce the reinstatement of sucrose-seeking behavior.