A Proteomic Approach for Quantitative Analysis of Calcitonin Gene-related Peptides in the Cerebrospinal Fluid Obtained from a Rat Model of Chronic Neuropathic Pain

Background: This study was conducted to quantitatively analyze proteins associated with the calcitonin gene-related peptide (CGRP) in cerebrospinal fluid (CSF) that was obtained from a rat model of chronic neuropathic pain following administration of intrathecal $CGRP_{8-37}$. Methods: Male Sprague-Dawley rats (100-150 g, 5-6 wks) were divided into two groups, sham controls and neuropathic pain models. At the time of operation for neuropathic pain model, an intrathecal catheter was threaded through the intrathecal space. At 1 or 2 wks after the operation (maximum pain state), a test dose of 1, 5, 10, or 50 nM of $CGRP_{8-37}$ was injected into the intrathecal catheter and the CSF was then aspirated. Conventional proteomics to evaluate the CSF were then performed using high resolution 2-D, gel electrophoresis followed by computational image analysis and protein identification by mass spectrometry. Results: Treatment with $CGRP_{8-37}$ effectively alleviated mechanical allodynia in a dose dependent manner. The most effective response was obtained when a dose of 50 nM was administered, but significant differences were obtained following administration of only 5 nM $CGRP_{8-37}$. Furthermore, the results of the proteomic analysis were consistent with the experimental results. Specially we detected 30 differentially expressed spots in 7 images when 2-D gel electrophoresis was conducted. The intensity of 6 of these spots (spot number: 20 and 26-30) was found decrease the $CGRP_{8-37}$ dose increased; therefore, these spots were evaluated by mass spectrometry. This analysis identified 2 different proteins, CGRP (spot numbers: 26-30) and neurotensin-related peptide (spot number: 20). Conclusions: The results of this study suggest that CGRP plays a role in chronic central neuropathic pain and is a major target of chronic neuropathic pain management.

만성 신경병성 통증이 유발된 쥐의 뇌척수액에서 단백체학을 이용한 Calcitonin Gene-related Peptides의 정량분석