Cervical sympathetic trunk transection affects inducible nitric oxide synthase expression in rat hippocampus following focal cerebral ischemia/reperfusion injury

BACKGROUND: The stellate ganglion block (SGB) plays a protective role in focal cerebral ischemia/reperfusion injury. The human SGB can be simulated by transection of the cervical sympathetic trunk (TCST) in rats.OBJECTIVE: To observe the effects of TCST on inducible nitric oxide synthase (iNOS) levels and cerebral infarct wolume in the hippocampus of rats with cerebral ischemia/reperfusion injury, and to analyze the mechanism of action.DESIGN, TIME AND SETTING: A completely randomized, controlled, neuropathological experiment was performed at the Institute of Neurological Disease, Taihe Hospital, Yunyang Medical College between March and September 2006.MATERIALS: A total of 93 Wistar rats, aged 17-18 weeks, of either gender, were used for this study. 2, 3, 5-triphenyl tetrazolium chloride was purchased from Changsha Hongyuan Biological Reagent Company, China. Rabbit iNOS antibody and goat anti-rabbit lgG antibody were the products of Wuhan Boster Biological Reagent Co., Ltd., China.METHODS: Ten rats were randomly selected for the sham-operated group. Cerebral ischemia/reperfusion injury was induced by middle cerebral artery occlusion (MCAO) using the suture method in the remaining rats. Forty successful rat models were randomly and equally divided into the following two groups: (1) TCST group: subsequent to TCST, MCAO was performed for 2 hours, followed by 24 hours reperfusion; (2) model group: rats underwent experimental procedures similar to the TCST group, with the exception of TCST. Rats in the sham-operated group were subjected to experimental procedures similar to the model group; however, the thread was only introduced to a depth of 10 mm.MAIN OUTCOME MEASURES: Following 24 hours of reperfusion, functional neurological deficits were scored. Brain tissue sections from ten rats of each group were used to measure cerebral infarct volume by TTC staining. Hippocampal tissue sections of an additional ten rats from each group were used to detect iNOS levels using the streptavidin-peroxidase immunohistochemistry method. Experimental data were expressed as absorbance values.RESULTS: Of the 93 selected rats, 50 were included in the final analysis. After MCAO for 2 hours, followed by 24 hours reperfusion, the absorbance values of iNOS-immunoreactive product were significantly greater in the model group compared to the TCST and sham-operated groups (P < 0.05). However, there was no difference between the TCST and sham-operated groups (P > 0.05). In addition, cerebral infarct volume in the model group was significantly greater compared to the TCST group (P < 0.05). The TCST group performed with lower total functional neurological scores compared to the model group (P < 0.05).CONCLUSION: TCST protects the brain against focal cerebral ischemia/reperfusion injury by possibly down-regulating hippocampal iNOS expression.