Evaluation of Neuropathic Pain in a Rat Model of Total Brachial Plexus Avulsion from Behavior to Brain Metabolism

• Published in: Pain physician 2019-05, Vol.22 (3), p.E215-E224
• Main Authors: Shen, Jun, Huo, Bei-Bei, Zheng, Mou-Xiong, Hua, Xu-Yun, Shen, Hao, Lu, Ye-Chen, Jiang, Dong-Lang, Shan, Chun-Lei, Xu, Jian-Guang
• Format: Article
• Language: English
• Subjects: Animals; Brachial Plexus - injuries; Brain - metabolism; Brain - pathology; Brain - physiopathology; China; Disease Models, Animal; Glucose; Male; Metabolism; Neuralgia - metabolism; Neuralgia - pathology; Neuralgia - physiopathology; Pain; Positron Emission Tomography Computed Tomography; Rats; Rats, Sprague-Dawley; Spinal cord; Spinal Cord - metabolism; Spinal Cord - pathology; Spinal Cord - physiopathology; Surgery; Tomography
• ISSN: 1533-3159; 2150-1149
• DOI: 10.36076/PPJ/2019.22.E215

Approximately 30% to 80% of patients with brachial plexus avulsion (BPA) developed neuropathic pain. It is an intolerable neuropathic pain, which brings heavy burden to family and society. In addition to motor and sensory deficits, neuropathic pain can be another serious sequela that equally influences the patient. The development of a microsurgical technique has promoted the treatment and rehabilitation of brachial plexus injury, but pain relief after BPA is still a difficult problem. The present study aimed to semi-quantify changes in the behavior, spinal cord and cerebral metabolism in a neuropathic pain model following BPA injury in rats. Controlled animal study. Institute of Rehabilitation Medicine, Shanghai, China. A total of 15 Sprague-Dawley rats, weighing 200 to 220 g, were randomly divided into 2 groups: experimental group (n = 10) and control group (n = 5). In the experimental group, neuropathic pain induced by BPA was established by directly avulsing the C5, C6, C7, C8, and T1 roots on the right side from the spinal cord. Rats in the control group only received open-close surgery. The autotomic behavior of biting their own digits was recorded and scored at 2 months after the surgery. Small animal positron emission tomography/computed tomography (PET/CT) images after injection of a 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) tracer were acquired to evaluate glucose metabolism in pain-related brain regions before and after the surgery, respectively. Semi-quantitative values of cortical to cerebellum standardized uptake value (SUV) ratios were calculated. Then, the animals were euthanized and the cervical segments of the spinal cord were removed for detection of glial fibrillary acidic protein (GFAP) expression in the astrocytes by immunohistochemical assay. Nine of the 10 rats (90%) in the experimental group showed autotomic behavior at 2 months after the surgery. Slight autotomic behavior was noted only in one of 5 rats (20%) from the control group. The autotomic score in the experimental group was significantly higher than that in the control group (5.4 ± 1.0 vs. 0.2 ± 0.4, P < 0.05). The experimental group showed significantly higher SUV ratio in both the right and left thalamus, compared to the control group (P < 0.05). Immunohistochemical assay demonstrated that GFAP positive astrocytes in the dorsal horn at the injured side significantly increased compared to the control group (P < 0.05). There are differences between small animals and human