RESUMO
BACKGROUND: Compound betamethasone injection has been widely used to treat intervertebral disc herniation, but its precise mechanism remains unclear. OBJECTIVE: To explore effects of local injection of compound betamethasone on substance P and calcitonin gene-related peptide in spinal cord and dorsal root ganglia of rat models undergoing autologous transplantation of nucleus pulposus. METHODS: A total of 36 Sprague-Dawley rats were randomly assigned to four groups: blank group, model group, sham surgery group, and western medicine group, with 9 rats in each group. After 1 week of adaptive feeding, rat models of autologous transplantation of nucleus pulposus were established in the model and western medicine groups. At 3, 7 and 12 days after surgery, the rats were given 128.25 μL saline in the model and sham surgery groups. The rats in the western medicine group were administered Betamethason Compound Injection 13.5 μL + 2% Lidocaine Injection 67.5 μL. At 12 hours after final administration, L4-6 segments of the spinal cord and dorsal root ganglion were obtained, and substance P and calcitonin gene-related peptide contents in L4-6 segments of the spinal cord and dorsal root ganglion were determined using immunofluorescence staining. RESULTS AND CONCLUSION: Significant differences in mean fluorescence intensity of substance P and calcitonin gene-related peptide were detected in rat spinal cord and dorsal root ganglion in each group (P < 0.01). Further paired comparison showed that compared with the blank and sham surgery groups, substance P and calcitonin gene-related peptide contents were significantly higher in the spinal cord and dorsal root ganglion in the model group (P < 0.01), which verified that models could be replicated and were reliable. Compared with the model and sham surgery groups, substance P and calcitonin gene-related peptide contents were significantly lower in the spinal cord and dorsal root ganglion of rats in the western medicine group (P < 0.01). Above results confirmed that Compound Betamethasone Injection for treating lumbar intervertebral disc herniation eliminated substance P and calcitonin gene-related peptide in dorsal root ganglion possibly by inhibiting dorsal root ganglion neuron synthesis and secreting substance P and reduced their transmission to the spinal cord, resulting in inhibiting and lessening pain.