The Role Of Projecting Neurons From Basolateral Amygdala To Nucleus Accumbens In Chronic Pain Induced Motivation Deficits

Chronic pain is an illness and does not have such a protecting function.Patients with chronic pain not only endure long-term pain,but also suffer from emotional disorders and cognitive deficits,such as anxiety,depression,motivation decline,dysmnesia and learning disability.The underlying mechanism remains unclear.In this study,we sought to explore the mechanism of motivational deficit associated with chronic pain in a mouse model of neuropathic pain with spared nerve injury(SNI).We found that two weeks after SNI surgery,neuropathic mice showed a significant motivation decline.Thus,the SNI mice completed less trials and touched less targeted screen in the progressive ratio task(PR task),a classical motivation-related task,compared to the sham control mice.But they did not show any anxiety-and depression-like behaviors four weeks after SNI surgery.Using fiber photometry technology,we found that the activity of the projection neurons from the basolateral amygdala(BLA)to the nucleus accumbens(NAc)was significantly increased when the mice receiving the reward of food,with a greater increment during the second half of the PR task.In the pain group,the augmentation in the signal from the projection neurons during reward receiving period was significantly reduced after the SNI surgery.The neural activity also tended to be weaker in the neuropathic mice than that in the sham mice.But we didn't find any change of calcium signal from the projection neurons when mice finished PR trials,started next trials or touched the screen.We also find the calcium signa of the projection neurons from BLA to m PFC didn't change when the mice receiving the reward of food.Therefore,our data suggest that the changes in the activity of the projecting neurons from the BLA to the NAc is involved in the motivational deficit caused by chronic pain.The detailed cellular and synaptic mechanisms warrants further study.