| Objective:Endotoxic shock (ES) is a serious systemic syndrome, which eventually causes multiple organ dysfunction syndrome (MODS) or even multiple organ failure (MOF), and then leads to a high mortality. Brain disorder often develops in sustained ES, yet the underlying mechanisms remain unclear. Oxidative stress is regarded as one of the leading factors causing tissue impairments in ES. ES results in excessive production of free radicals, nitric oxide (NO) and peroxynitrite (ONOOˉ). These mediators can cause injuries to cells and tissues and contribute to the pathological consequences of shock. In addition, NO mediates the neurotoxic effects of excitatory amino acids which play a vital role in hypoxia and/or ischemic brain damage. Cholecystokinin-octapeptide (CCK-8), a brain-gut peptide, was reported to have protective effects on ES animals. Studies showed that CCK-8 could reverse the hypoactivity of blood vessels induced by lipopolysaccharide (LPS), the main component of endotoxin. CCK-8 could protect lung, liver, heart, spleen against injuries induced by LPS and inflammatory mediators. So, whether or not CCK-8is capable of attenuating brain injury in ES deserves studies. In this study, ES model was established to evaluate the roles of CCK-8 in alleviating the LPS-induced brain injury, and its likely mechanisms were preliminarily studied.Methods:Rabbits were anesthetized with 25% urethane (1mg/kg, iv). The left common carotid artery and right cervical vein were isolated and cannulated for measuring mean arterial pressure (MAP) and administrationt of agents. Animals were divided randomly into four groups(eight per group): ①control group: the same volume of saline was administrated intravenously; ②LPS group: LPS ( 8mg/kg, 8mg/ml) was injected , obvious reduction of MAP indicated the development of ES; ③CCK-8+LPS group: CCK-8 (15μg/kg, 1mg/ml) was injected 30min before the administration of LPS; ④ Proglumide (Pro)+LPS group: Pro (1mg/kg, 1mg/ml), a nonspecific antagonist of CCK receptors was injected 30min before the administration of LPS. MAP was observed and recorded before and 30min, 1h, 1.5h, 2h, 3h, 4h, 5h after the administration of saline, LPS, CCK-8+LPS, Pro+LPS. Blood samples were taken before and 1h, 3h, 5h after the administration of the agents. Rabbits were sacrificed at 5h and brain tissue samples were obtained. Contents of NO and malondialdehyde (MDA), activities of nitric oxide synthase (NOS) and superoxide dismutase (SOD) were measured in plasma and brain tissues (cerebral cortex and hippocampus). Morphological changes in brain wereobserved through light microscope (LM) and transmission electron microscope (TEM). Rats were anesthetized with 10% chloral hydrate (350mg/kg, ip). Animals were divided randomly into four groups (three per group): ①control group: the same volume of saline was administrated; ②LPS group: LPS ( 8mg/kg) was injected; ③CCK-8+LPS group: CCK-8 (40μg/kg) was injected 30min before the administration of LPS; ④ Pro+LPS group: Pro (1mg/kg) was injected 30min before the administration of LPS. All agents were injected with through sublingual vein. Brain samples were obtained 6h after the administration of agents. Brain coronal sections were processed for immunohistochemical analysis to observe the expression and distribution of iNOS and nNOS protein. Data are expressed as mean±SD. Differences among groups were tested by one-way analysis of variance (ANOVA) followed by a least significant difference (LSD) test when significant differences were detected. P values of less than 0.05 were considered statistically significant.Results:There was no difference in MAP among these groups before treatment. Compared with control group, LPS administration resulted in significant reduction in MAP from 30min to 5 hour (P<0.01). CCK-8 pre-administration could elevate MAP and maintain it at a higher level than that of LPS group (P<0.05, P<0.01). In Pro+LPS group, there was a tendency of further decline in MAP compared with LPSgroup, but no statis...
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