Changes of autonomic nervous active substances in myocardium of rats with acute high-level spinal cord injury / 中华创伤杂志

ABSTRACT

Objective:To investigate the changes of autonomic nervous active substances in myocardium of rats with acute high-level spinal cord injury.Methods:Twenty-four clean-level healthy adult male SD rats weighting 250-300 g for 8-10 weeks old were divided into control group ( n=6) and spinal cord injury group ( n=18) according to the random number table. The spinal cord injury group was subdivided at 4, 12 and 24 hours, with 6 rats at each time point. The high-level spinal cord injury model was established by the modified Allen′s weight-drop method, and the spinal cord was only exposed in control group. The postoperative performance and BBB score for limb movement were observed in each group. The myocardium of each group was resected and used to observe ultrastructure of myocardial cells under transmission electron microscope and detect protein and mRNA levels of tyrosine hydroxylase (TH), noradrenaline transporter (NET), acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) by Western blot and RT-PCR analysis. Results:Rats of control group showed normal limb motion after operation without significant change from the preoperation level, and mean BBB score was 21 points. Rats of spinal cord injury group showed significantly reduced activities and feeding, with flaccid paralysis of both lower limbs as well as no spontaneous excretion, and showed BBB score of 0 point at 4 hours and 12 hours after injury, which was increased slightly at 24 hours after injury, with the highest score for 1 point. The ultrastructure of myocardial cells showed no obvious abnormalities in control group, while different degrees of changes in spinal cord injury group. Compared with control group, Western blot analysis showed that protein levels of TH and NET were decreased, while AChE and ChAT were increased in spinal cord injury group ( P<0.05 or 0.01). Compared with control group, RT-PCR analysis showed that mRNA levels of TH and NET were decreased, while AChE and ChAT were increased in spinal cord injury group ( P<0.05 or 0.01). mRNA levels of TH and NET in spinal cord injury group at 24 hours after injury were significantly different from those at 4 hours and 12 hours after injury (all P<0.05). mRNA levels of ChAT in spinal cord injury group were statistically significant at 12 hours and 24 hours after injury from those at 4 hours after injury, with significant difference at 12 hours and 24 hours after injury (all P<0.05). Conclusion:Sympathetic nerve active substances TH and NET are down-regulated but vagal nerve active substances AChE and ChAT up-regulated in myocardium of rats with acute high-level spinal cord injury, which may be related to the relative excitation of the parasympathetic nerve blocking the sympathetic innervation of the higher center to the heart following high-level spinal cord injury.