Cheng, M; Fang, CY; Li, N; Ma, J; Meng, D; Wang, Y; Zhang, GX
OBJECTIVE To investigate the mRNA expression changes of neurite outgrowth inhibitor-A (Nogo-A), calcitonin gene-related peptide (CGRP) and CGRP receptor in the periaqueductal gray of formaldehyde-induced inflammatory rats. METHODS The hyperalgesia of inflammation was induced in rats by receiving 2% formaldehyde (sc 0.1 ml) in the unilateral hindpaw hypodermically. On the 3rd day, hindpaw withdrawal latencies in response to both the thermal and mechanical stimulation were measured, and on the 3rd and 7th days respectively after inflammation the periaqueductal gray of rats was separated. The real-time quantitative PCR was used to detect mRNA expression of Nogo-A, CGRP, calcitonin receptor-like receptor (CLR), and receptor activity-modifying proteins 1 (RAMP1) in the periaqueductal gray of rats. RESULTS There was gene expression of Nogo-A, CGRP, CLR and RAMP1 in the periaqueductal gray of normal rats. On the 3rd day after inflammation, compared with the control group, the hindpaw withdrawal latencies in response to both thermal and mechanical stimulation significantly decreased (P<0.01), the mRNA expression of Nogo-A significantly decreased (P<0.01), and the expression of CGRP, CLR and RAMP1 was significantly increased (P<0.01) in the periaqueductal gray of inflammatory rats. On the 7th day after inflammation, the CGRP mRNA expression returned to the level of normal rats, but the mRNA expression level of Nogo-A, CLR and RAMP1 didn't. The level of Nogo-A was lower (P<0.01), but that of CLR and RAMP1 was still higher (P<0.01) than normal levels. CONCLUSION The mRNA expression of Nogo-A significantly decreases, but the expression of CGRP, CLR and RAMP1 significantly increases in the periaqueductal gray of formaldehyde-induced inflammatory hyperalgesia rats. Along with the relief of inflammation, the mRNA expression of CGRP gradually returns to normal. These changes may be related to the process of inflammation or pain modulation in rat periaqueductal gray.
CSA Neurosciences Abstracts; Genetics Abstracts; Biochemistry Abstracts 2: Nucleic Acids; Toxicology Abstracts; Pain perception; Axonogenesis; Periaqueductal gray area; Inflammation; Gene expression; Receptor activity modifying proteins; Formaldehyde; Calcitonin gene-related peptide; Nogo protein; Polymerase chain reaction; Calcitonin; Mechanical stimuli; N 14810:Methods; N3 11028:Neuropharmacology & toxicology; X 24350:Industrial Chemicals; G 07710:Chemical Mutagenesis & Radiation