| Research Abstract |
The purpose of this study is to examine whether anandamide, an endogenous cannabinoid receptor ligand, is involved in the pathogenesis of septic encephalopathy. Male Wistar rats (7 weeks old) were randomly divided into four groups : Group 1, control (0.5ml of saline injected subcutaneously) ; Group 2, sham (surgical abdominal incision and suturing was performed, but ligation and puncture of the cecum was omitted) ; Group 3, cecal ligation and puncture (CLP) ; Group 4, CLP + AM281 {(N-morpholin-4-yl)-5-(2,4--yl)-5-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide)} as the cannabinoid receptor antagonist [1mg/kg i.p]. Sepsis was induced by CLP under pentobarbital anesthesia (10mg/kg i.p.) with 1% isoflurane. A 2 Fr high-fidelity micromanometer catheter was inserted into the left ventricle via the right carotid artery to assess hemodynamics. Each of the rats was neurologically assessed at 30min, 12, 24 and 48h after the treatment. The cytoplasmic levels of caspase-3 in the hippocamp
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i were assayed before, and at 30min, 24 and 48h after surgery, using Western blotting techniques. To examine the effects of AM 281 on neurologic function and mortality rate, we set another control group treated solely with AM 281. Selective inducible nitric oxide synthase (NOS) inhibitor, L-N6-(1-iminoethyl)-lysine (L-NIL) (4mg/kg), was injected intraperitoneally immediately after CLP to produce the CLP+ L-NIL group to exclude the influence of depressed hemodynamics on neurological impairment. It was found that administration of AM 281 could prevent the hemodynamic changes induced by sepsis. Reflex responses, including the pinna, corneal, paw or tail flexion and righting reflexes and the escape response significantly decreased in, the CLP and CLP+ L-NIL groups at 48 h after the surgery. In contrast, no changes in these reflex responses were found between the CLP+ AM 281 and control and sham groups. In addition, no effects of the administration of AM 281 on neurologic function and mortality rate in control group. Tissue caspase-3 levels were elevated at 48h after CLP in the CLP alone group (Control, 3.9±0.4; sham, 4.2±0.4; CLP, 7.1±1.0^*; CLP+AM 281, 4.0±0.5 densitometric units ; means±SD. ^*p<0.01). In addition, administration of AM 281 also improved the mortality rate (p<0.05).
Administration of AM 281 prevented the hemodynamic changes and development of neurological dysfunction occurring in association with septic shock ; and could improve the mortality rate in experimentally induced septic shock in rats. Although further studies are necessary to determine whether endogenous cannabinoids cause septic encephalopathy in rats directly or via their effects on systemic hemodynamics, the beneficial effects of AM 281 on these rats might have significant therapeutic implications in cases of septic encephalopathy. Less
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