Humans ; Neurosurgical Procedures ; methods ; Obesity ; Tracheostomy ; methods

Objective To investigate the iNOS expression in cerebral aneurysm tissue, and the effect of selective iNOS inhibitor aminoguanidine on experimental cerebral aneurysm formation and serum NO production. Methods Fifty SD rats were divided into 3 groups randomly. To reproduce the aneurysm model, 40 adult male rats (weight, 250-300g) were subjected to ligation of the left common carotid artery and the posterior branches of both renal arteries. One week after the operation, 1% saline was given for drinking to substitute plain water. Each rat received an intraperitoneal injection of aminoguanidine (100mg/kg)(group A, n=20) or normal saline (group B, n=20) beginning in the morning of postoperative day(POD) 1 through POD 150. Group C rats received no operation to serve as the control group (n=10). Arterial wall at the bifurcation of the right anterior cerebral artery and olfactory artery as well, as serum were harvested after 5 months. Blood pressure was measured before the experiment and 5 months after the experiment procedure. NO levels were indirectly quantified by measuring nitrate levels. The incidence of formation of aneurysm, pathological findings and expression of iNOS in aneurysmal wall were evaluated with HE staining and immunohistochemical analysis. Results Selective iNOS inhibitor aminoguanidine could significantly inhibit the formation of aneurysms and lower serum levels of nitrate. The pathological features of the experimental aneurysms were similar to that in human, including discontinuation or disappearance of tunica intima, thinning or disappearance of the elastic and muscular layers, and substitution of artery wall by a layer of fibrous connective tissue. iNOS immunoreactivity could be seen in the smooth muscle cells of the intimal pad and distal portion of the newly formed aneurysm. Conclusion Cerebral aneurysm can be induced in rats by alteration in hemodynamics, and it is related to formation of local expression of iNOS and high NO level.