Role of spinal neuronal Mas-related gene receptor C in maintenance of bone cancer pain in mice

Abstract

Objective To evaluate the role of spinal neuronal Mas-related gene receptor C (MrgC) in the maintenance of bone cancer pain (BCP) in mice. Methods A total of 132 SPF male C3H/HeJ mice, aged 8-10 weeks, weighing 18-22 g, were randomly divided into 4 groups (n=33 each) using a random number table: sham operation group (S group), BCP group, bovine adrenal medulla peptide 8-22 (BAM8-22, a highly selective MrgC agonist) group (group BAM), and MrgC antibody group (group MA). BCP was produced by injecting α-MEM 20 μl containing 2×105 NCTC2472 cells into the distal medullary cavity of right femur bone.While α-MEM 20 μl was injected only in group S. The artificial cerebrospinal fluid 5 μl was injected intrathecally in S and BCP groups, and BAM 8-22 8 nmol/5 μl and MrgC antibody 5 μl were injected intrathecally in BAM and MA groups, respectively, once a day for 7 consecutive days starting from the day 14 after inoculation of the tumor cells.At 1 day before inoculation (T0), before administration (T1), and at 14, 16 19 and 21 days after inoculation (T2-5, at 0.5 h before the initial administration and 2 h after each administration), the number of spontaneous flinches (NSF) and mechanical paw withdrawal threshold (MWT) were measured.Five animals selected from each group at each time point were sacrificed, and the lumbar enlargement segments of the spinal cord were removed for determination of MrgC expression in the spinal neurons (by immunofluorescence). Results Compared with group S, NSF was significantly increased, MWT was decreased, and the expression of MrgC was up-regulated at T1-5 in BCP, BAM and MA groups.Compared with group BCP, NSF was significantly decreased, MWT was increased, and the expression of MrgC was up-regulated at T2-5 in group BAM, and NSF was significantly increased, MWT was decreased, and the expression of MrgC was down-regulated at T2-5 in group MA. Conclusion Spinal neuronal MrgC is involved in the maintenance of BCP in mice. Key words: Receptors, G-protein-coupled; Bone neoplasms; Pain; Neurons; Spinal cord