Effects of NG-nitro-L-arginine on focal cerebral ischemic injury in rats

BACKGROUND： Previous researches have proved that aminoguanidin can cure cerebral ischemic injury remarkably as a selective induced nitricoxide synthase （iNOS） inhibitor. However, whether nonselective NOS inhibitor could protect cerebral ischemic injury or not is unclear. OBJECTIVE： To investigate the effects of NG-nitro-L-arginine （L-NA）, a nonselective nitricoxide synthase （NOS） inhibitor, on cerebral ischemic injury of rats and the possible mechanism.DESIGN： Randomized controlled study.SETTING ： Pharmacological Department of Medical Academy of Science of Hebei Province.MATERIALS： A total of 56 male healthy SD rats, of grade Ⅱ, weighting 250-290 g, were provided by the Experimental Animal Center of Hebei Province （certification： 04036）. METHODS： The experiment was completed in the Pharmacological Department of Medical Academy of Science of Hebei Province from March 2005 to January 2006.① Grouping： Rats were randomly divided into 3 groups： sham operation group （n=8）, model group （n=24） and L-NA group （n=24）.② Modeling： Middle cerebral artery （MCA） was established on rats in model group and L-NA group with intreluminal line occlusion methods, and rats in sham operation group were separated their external carotid arteries without occlusion of internal carotid artery. ③ Intervention study： Rats in model group and L-NA group were injected intreperitoneally with 10 mL/kg and 20 mg/kg L-NA at 2, 6 and 12 hours respectively after ischemia twice a day for 3 consecutive days. ④ Rats were sacrificed on the third day for measuring volume of cerebral infarction with image analysis and swelling degrees and activities of mitochondria with electron microscope. Effect of L-NA on ultrastructural changes of neurons in cortex was observed after ischemia. MAIN OUTCOME MEASURES：① Volume of cerebral infarction; ②Swelling degrees, contents of nitric oxide （NO） and malondialdehyde （MDA） and activities of adenosine triphosphatase （ATPase）, superoxide dismutase （SOD） and glutathione peroxidase （GSH-Px） in mitochondria;③ Ultrastructural changes of mitochondria in brain tissue after cerebral ischemia. RESULTS： ① At 12 hour after ischemia, volume of cerebral infarction in L-NA group was lower than that in model group （P 〈 0.01）. ② Content of NO in mitochondria in L-NA group was decreased as compared with that in model group at 2, 6 and 12 hours after ischemia （P 〈 0.05）; swelling degree of mitochondria in brain tissue was relieved in L-NA group at 12 hour after ischemia, and content of MDA was decreased （P 〈 0.05）; mitochondrial activity in L-NA group was increased at 12 hour after ischemia, and activities of ATPase, SOD and GSH-Px in mitochondria were increased （P 〈 0.05）.③ Degrees of mitochondrial injury in brain tissue were relieved in L-NA group at 12 hour after ischemia as compared with those in model group and L-NA group at 2 and 6 hours after ischemia. CONCLUSION ： ①L-NA can beneficially inhibit NO production, but not protect brain against damage in ischemia acute stage. ②L-NA might have protective effects on cerebral injury through inhibiting the production of oxygen free radical, increasing antioxidation, ameliorating energy metabolism, beneficially improving the integrity of form and function of mitochondria in brain tissue during postischemia in rats.

Purinergic contraction of the rat vas deferens in L-NAME-induced hypertension：effect of sildenafil

Hypertension （HTN） is a risk factor for erectile dysfunction, but its effect on vas deferens （VD） contractility and the ejaculatory response has not been delineated. NG-nitro-L-arginine methyl ester （L-NAME）, a nitric oxide synthase inhibitor, was used for induction of nitric oxide （NO）-deficient HTN. Our aim was to evaluate the effects of L-NAME-induced HTN on rat VD contractility and to determine whether sildenafil affects VD contractility. A total of 36 male rats were divided into （1） control, （2）L-NAME-HTN, （3） sildenafil treated L-NAME-HTN groups. Group 2 was treated with L-NAME （40 mg kgI per day） in drinking water for 4 weeks. Group 3 received sildenafil （1.5 mg kg^-1 per day, by oral gavage） concomitantly with L-NAME. The prostatic portion of the VD was subjected to electrical field stimulation （EFS, 1-20 Hz）, and the P2X1 agonist α,β-methylene ATP （α,β meATP, 100 μmol L^-1-1 μmol L-1） and the al-adrenoceptor agonist phenylephrine （Phe, 100 μmol L^-1-1 mmol L^-1） were used to construct concentration-response curves. These experiments were repeated in the presence of P2X receptor antagonist, pyridoxalphosphate-6-azophenyl-2＇,4＇-disulfonic acid （PPADS, 30 μmol L-1）. VD contractions in response to EFS, a,β-meATP and Phe were significantly enhanced by L-NAME. Sildenafil treatment in the L-NAME group improved the contractile response of VD to EFS （20 Hz）. In the presence of PPADS, the enhanced contractile response of VD to EFS and a,β-meATP in hypertensive rats was reversed. In the rat model of chronic NO depletion, the purinergic and adrenergic components and EFS affect VD contractility. The VD contractile response may be mediated more by the purinergic system than the adrenergic system, and sildenafil may alter the ejaculatory response in men with PE.