Involvements of galanin and its receptors in antinociception in nucleus accumbens of rats with inflammatory pain

This study tested the hypothesis that antinociceptive effects of galanin and its receptors in nucleus accumbens (NAc) of rats with inflammatory pain provoked by subcutaneous injection of 0.1 ml of 2% carrageenin into the sole of the rat's left hindpaw. The hindpaw withdrawal latencies (HWLs) in response to thermal and mechanical stimulation significantly decreased in bilateral hindpaws at 3 and 4 hour after a subcutaneous injection of carrageenin. However intra-NAc injection of 2 and 3 nmol, but not 1 nmol of galanin markedly induced an increase in the HWLs in a dose-dependent way. Western blot also showed, that the expression of galanin receptor 1 (GalR1) and galanin receptor 2 (Ga1R2) were significantly upregulated in NAc at 3 hour after a subcutaneous injection of carrageenin. In addition, the rats were intra-NAc injected galanin, 5 min later following by intra-NAc injection of galanin receptor antagonist galantide, the galanin-induce antinociceptive effects were suppressed by galantide. The results demonstrated that galanin and its receptors might be involved in antinociception in the NAc of rats with inflammatory pain. (C) 2015 The Authors. Published by Elsevier Ireland Ltd.

本研究验证了以下假说：在大鼠左后爪足底皮下注射0.1毫升2%角叉菜胶引发炎性疼痛的情况下，甘丙肽及其受体在大鼠伏隔核（NAc）中具有抗伤害感受作用。皮下注射角叉菜胶后3小时和4小时，双侧后爪对热刺激和机械刺激的缩爪潜伏期（HWLs）显著缩短。然而，向伏隔核内注射2和3纳摩尔（而非1纳摩尔）的甘丙肽以剂量依赖的方式显著导致缩爪潜伏期增加。蛋白质印迹法也显示，皮下注射角叉菜胶后3小时，伏隔核中甘丙肽受体1（GalR1）和甘丙肽受体2（GalR2）的表达显著上调。此外，在向大鼠伏隔核内注射甘丙肽5分钟后，接着向伏隔核内注射甘丙肽受体拮抗剂加兰他敏，甘丙肽诱导的抗伤害感受作用被加兰他敏抑制。结果表明，甘丙肽及其受体可能参与炎性疼痛大鼠伏隔核的抗伤害感受过程。（C）2015作者。由爱思唯尔爱尔兰有限公司出版。