Background and PurposeWe previously reported that L-arginine infusion increased pial vessel diameter by nitric oxidedependent mechanisms, improved regional cerebral blood flow (rCBF) distal to middle cerebral artery (MCA) occlusion, and reduced infarction volume in spontaneously hypertensive rats when administered intraperitoneally before and after MCA occlusion. In this report we extend our findings (1) by examining the time course of L-arginine on rCBF and pial vessel diameter under basal conditions and on rCBF after MCA occlusion and (2) by reproducing the protective effect of L-arginine on infarct volume when given intravenously immediately after the onset of MCA occlusion in both normotensive and hypertensive models of focal cerebral ischemia.Methods Changes in pial vessel diameter (closed cranial window) and rCBF (laser-Doppler flowmetry) were measured over time after L-arginine infusion into anesthetized Sprague-Dawley rats. rCBF was also measured distal to MCA occlusion in a brain region showing rCBF reductions in the range of 80% of baseline. The effects of infusing L-arginine (300 mg/kg for 10 minutes beginning 5 minutes after occlusion) were assessed on infarction volume in Sprague-Dawley rats after proximal MCA occlusion and in spontaneously hypertensive rats after common carotid artery plus distal MCA occlusion.
Summary:We examined whether 7-nitroindazole (7-NI), a putative inhibitor of neuronal nitric oxide synthase (nNOS), decreases cerebral infarction 24 h after proximal middle cerebral artery (MCA) occlusion. In preliminary experiments, we determined that 7-NI (25, 50, and 100 mg/kg i.p.) decreased nitric oxide synthase (NOS) activ ity within cerebral cortex by 40-60% when measured up to 120 min, but not 240 min after administration. At 25 or 50 mg/kg, 7-NI did not alter the systemic arterial blood pressure or the dilation of pial arterioles after topical ace tylcholine (10 and 100 j-LM). To examine the effect of 7-NI on infarct size, 55 Sprague-Dawley halothane anesthetized rats were subjected to proximal MCA occlu sion (modified Tamura method). Five minutes after oc clusion, 7-NI (25 or 50 mg/kg i.p.) or vehicle was injected. Animals treated with 25 or 50 mg/kg showed 25 and 27%
The authors studied the venous drainage system and its impairment in relation to risk of hemorrhage in 108 cases of supratentorial arteriovenous malformation (AVM). The proportion of AVM's undergoing hemorrhage (hemorrhagic rate) was calculated in relation to: 1) the number of draining veins (one, two, or three or more); 2) the presence or absence of impairment in venous drainage (severe stenosis or occlusion in draining veins); and 3) the location of draining veins (deep venous drainage alone, superficial venous drainage alone, or a combination of the two). Statistical analysis demonstrated that AVM's with the following characteristics had a high risk of hemorrhage: 1) one draining vein (hemorrhagic rate 89% in 54 patients); 2) severely impaired venous drainage (hemorrhagic rate 94% in 18 patients); and 3) deep venous drainage alone (hemorrhagic rate 94% in 32 patients). The present study suggests that the venous drainage system of AVM's is significantly associated with the risk of hemorrhage of these lesions. Therefore, careful preoperative angiographic evaluation of the venous drainage system is mandatory for decision making in the management of patients with AVM's.
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