Miampamba M, Sharkey K A
Neuroscience Research Group, Department of Physiology and Biophysics, University of Calgary, Alberta, Canada.
J Auton Nerv Syst. 1999 Sep 24;77(2-3):140-51.
Fos expression induced by injection of dilute formalin (50 microl, 5% in physiological saline) into the colonic wall was examined in the myenteric plexus, lumbosacral spinal cord and brainstem of the rat. The aims of this study were (i) to determine whether neurons in these regions express Fos in response to the injection of formalin into the colon and (ii) to examine whether administration of an alpha 2 adrenoceptor agonist modulates Fos expression. Tissues were removed 2 h after the injection of saline or formalin. Saline injected in the colon induced Fos in enteric glia in the myenteric plexus. The number of Fos immunoreactive nuclei significantly increased in both myenteric neurons and enteric glia after the injection of formalin. Similarly, Fos immunoreactive neuronal nuclei were significantly increased in the spinal cord, area postrema and nucleus of the solitary tract after the injection of formalin. Pretreatment of rats with the alpha 2 adrenoceptor agonist xylazine (2, 4 and 8 mg/kg) 15 min before the injection of formalin, dose-dependently reduced the number of Fos immunoreactive neuronal and glial nuclei in the myenteric plexus, and neuronal nuclei in the spinal cord and brainstem. Simultaneous administration of xylazine (8 mg/kg) and the alpha 2 adrenoceptor antagonist yohimbine (1 mg/kg) reversed the effects of xylazine in the spinal cord and brainstem, but not in the myenteric plexus. These data show that injection of formalin in the colonic wall results in Fos expression in myenteric neurons and enteric glia, and neurons in the spinal cord and brainstem. This may be due to the direct chemical stimulation of the innervation of the colon and/or the subsequent acute colitis. The observed neuronal Fos expression can be modulated by an alpha 2 adrenoceptor agonist through noradrenergic pathways and/or reduction of the excitability of the enteric neural circuitry.
在大鼠的肌间神经丛、腰骶脊髓和脑干中，研究了向结肠壁注射稀释福尔马林（50微升，生理盐水中含5%）所诱导的Fos表达。本研究的目的是：（i）确定这些区域的神经元是否会因向结肠注射福尔马林而表达Fos；（ii）研究给予α2肾上腺素能受体激动剂是否会调节Fos表达。在注射生理盐水或福尔马林2小时后取出组织。向结肠注射生理盐水可诱导肌间神经丛中肠神经胶质细胞表达Fos。注射福尔马林后，肌间神经元和肠神经胶质细胞中Fos免疫反应性细胞核的数量显著增加。同样，注射福尔马林后，脊髓、最后区和孤束核中Fos免疫反应性神经元细胞核也显著增加。在注射福尔马林前15分钟，用α2肾上腺素能受体激动剂赛拉嗪（2、4和8毫克/千克）对大鼠进行预处理，剂量依赖性地减少了肌间神经丛中Fos免疫反应性神经元和神经胶质细胞核的数量，以及脊髓和脑干中神经元细胞核的数量。同时给予赛拉嗪（8毫克/千克）和α2肾上腺素能受体拮抗剂育亨宾（1毫克/千克）可逆转赛拉嗪在脊髓和脑干中的作用，但在肌间神经丛中则不能。这些数据表明，向结肠壁注射福尔马林会导致肌间神经元、肠神经胶质细胞以及脊髓和脑干神经元中Fos表达。这可能是由于结肠神经支配的直接化学刺激和/或随后的急性结肠炎所致。观察到的神经元Fos表达可通过α2肾上腺素能受体激动剂通过去甲肾上腺素能途径和/或降低肠神经回路的兴奋性来调节。
