The Death Mechanism And The Changes Of Neurotransmitters After Primary Brain Stem Injury

Craniocerebral injuries have been the main causes of human death in traffic accident and violence cases. Experts and scholars at home and abroad had pay close attention to it for many years. Generally speaking, rapid death caused by craniocerebral injury was chiefly due to the impairment and dysfunction of brain stem for it's the vital center of the body. We call it primary brain stem injury when one was impacted on the head and the brain stem was injured and fell fast into deep coma or death within minutes after impact. The function of nerve system is based on its special formation, depending on the transmission of neurotransmitters. The clinical manifestation and death immediately after brain stem injury had its substance foundation. If there was something wrong with the neurotransmitter transmission or the neurotransmitter itself, the function of the nerve system would be disorder. Based on animal experiments, the purpose of this study was to provide some evidence for the mechanism of the failure of brain stem function after craniocerebral injury and for diagnosis of brain stem injuries.Objective: To deduce the causes and mechanism of dying immediately and the failure of the brain stem function after craniocerebral injuries from the study of the expression of 5-HT and SP and the GABA synmetase GAD and GAD-mRNA.Material and Methods: A free-falling weight-drop device designedby Marmarou(1994) was used to impact the Wistar rats to establish the craniocerebral injury models. After ante-mortem impact, there were 14 who died within minutes after impact and 19 who survived from impact after a long deep coma. A postmortem impact group and a normal control group were both made up of 6 rats. All the rats were monitored by electrocardiograph during the whole period. Encheiresis was done on the aorta of all groups, washed by normal saline until clean water out, then perfused in by 4% paraformaldehyde for 30 minutes. Cut the skull open and took out the whole brain. Separated the brain stem from brain. Frozen it or embeded it in paraffin and sections were made and mounted on the slides. Hematoxylin and Eosin (HE) staining and immunohistochemical SABC staining were done on the paraffin sections to detect the changes of 5-HT expression in the raphe nuclei of the retricular formation of brain stem and the changes of Substance P (SP) and Glutamic Acid Decarboxylace (GAD) expression in the substantia nigra. To detect the changes of GAD65-mRNA and GAD67-mRNA expression in the substantia nigra, we used oligodeoxynucleotide probes and in situ hybridization histochemical methods on the frozen sections. The results of each groups were compared by using computerized image analysis system. The data was input into SPSS for Windows for statistics. Results:1. In the dead group, clinical manifestations caused by brain stem injury were obvious after impact, and gross pathological observations showed that there were dispersed spot hemorrhages in brain stem but not in the other three groups.2. HE staining: In the dead group rats, diffuse subarachnoid hemorrhage and edema and spot hemorrhage in brain parenchyma were observed. And edema with broadened intercellular space and dispersed spot hemorrhage and congestion in micrangium with edema around it could be observed in the brain stem. Though there were some diffuse subarachnoid hemorrhage and edema and spot hemorrhage in brain parenchyma in the survival group rats, nothing was changed in brain stem. In the postmortem impact group and the normal control group rats, nothing was changed of the brain parenchyma. 3. Immunohistochemical SABC staining:3.1 5-HT: In the death group rats' brain stems, not only the 5-HT energetic neures of raphe nuclei, but also the neurogliocyte and the mesenchymal cell and minute blood vessel in the retricular formation were 5-HT deposited abnormally, especially in that of the pons and the medullary oblongata. In contrast, the positive staining of 5-HT in the other three groups' brain stems were only located in the 5-HT e...