The effect of timing of clot removal on chronic vasospasm in a primate model

The effect of complete clot removal at times from 48 to 96 hours after subarachnoid hemorrhage (SAH) on the development of chronic cerebral vasospasm was evaluated to determine whether there is a critical point after which clot removal is ineffective in preventing vasospasm. Thirty cynomolgus monkeys were randomized to one of five groups: sham-operated group, clot removal at 48 hours after SAH (48-hour group), clot removal at 72 hours after SAH (72-hour group), clot removal at 96 hours after SAH (96-hour group), and clot placement only (clot group). Standard microsurgical techniques were used to dissect bilaterally the major cerebral arteries free of arachnoid. An autologous blood clot averaging 4.2 gm was placed around the vessels in the subarachnoid space of the monkeys in the 48-hour, 72-hour, 96-hour, and clot groups. Physiological saline was instilled into the subarachnoid space of the sham-operated animals. Animals in the clot-removal groups underwent surgical clot removal at the determined times for each group. Two animals in each of the sham-operated and clot groups were subjected to reoperation at each of 48, 72, and 96 hours after SAH. The incisions were reopened and then simply reclosed. Neurological status, angiographic cerebral vessel caliber, and physiological status were evaluated before and 7 days after SAH induction. There were no significant neurological deficits in the sham-operated, 48-hour, or 72-hour groups. Two animals in each of the 96-hour and clot groups showed deterioration in level of consciousness developing on Day 4 or 5 after SAH induction. All the major cerebral arteries of the animals in the clot and 96-hour groups showed significant vasospasm (p less than 0.01) on Day 7. Animals in the 72-hour group had significant vasospasm (p less than 0.05) of the internal carotid and middle cerebral arteries but not the anterior cerebral arteries. There was no significant vasospasm (p greater than 0.05) in any of the cerebral arteries in the 48-hour group. Severity of vasospasm paralleled the duration of contact between the blood clot and the cerebral vessels. Evacuation of the subarachnoid hematoma later than 48 hours after SAH resulted in no significant reduction in the degree of chronic cerebral vasospasm. It is suggested that clot removal at early operation is likely to be useful only if it is performed within 48 hours of SAH.     

Monoclonal antibody against E selectin attenuates subarachnoid hemorrhage-induced cerebral vasospasm

BACKGROUND: Increasing evidence indicates that inflammatory responses are implicated in the pathogenesis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH). However, the role of adhesion molecules in SAH-induced vasospasm is less clear. This study was designed to examine the effect of a highly specific antibody, monoclonal anti-E-selectin antibody, on cerebral vasospasm in a new murine SAH model. METHODS: Experimental SAH was induced in C57Black/6J mice by injecting autogenous blood into the cisterna magna, and anti-E-selectin antibody was administered intravenously immediately after SAH. All animals were killed by perfusion-fixation 24 hours after SAH. The diameters of anterior cerebral arteries (ACAs) were measured after arteries were cast with gelatin and india ink. Peripheral white blood cell count was also investigated. RESULTS: The average diameters of ACA were reduced by 22% and 25% in the SAH only and SAH plus vehicle groups, respectively, when compared with the healthy control group. After treatment with 12.5, 4, and 1 microg of anti-E-selectin antibody in mice subject to SAH, the average diameter of ACA was decreased by 9%, 10%, and 22%, respectively, when compared with the healthy control group. The protective effects of anti-E-selectin antibody achieved statistical significance at doses of 12.5 and 4 microg. Animals in the SAH only and SAH plus vehicle groups exhibited leukopenia. Administration of 12.5, 4, and 1 microg of anti-E-selectin antibody reduced leukopenia, and the total white blood cell count obtained in animals treated with 12.5- and 4-microg doses were significantly higher as compared with SAH animals. CONCLUSIONS: These findings provide the first evidence that anti-E-selectin antibody was effective in prevention of SAH-induced vasospasm and imply a possible role of E selectin in the pathogenesis of vasospasm after SAH.     

A new animal model for monitoring the early cerebral vasospasm after subarachnoid haemorrhage

AIM: Spasm of cerebral arteries is a complication associated with subarachnoid haemorrhage. The aim of the present work is to find an experimental model of reliable, simple and in vivo monitoring of 'early' basilar artery spasm after subarachnoid haemorrhage (SAH). Early spasm occurs within minutes of the SAH, its duration is approximately 1 hour. The need of different morphological and haemodynamic methods to evaluate experimental early spasm is reported. METHODS: To overcome intracranial surgical manipulations and biological of contrast and fixation media we designed a model that allows in vivo functional monitoring of basilar blood flow far away from the spasm without direct surgical and chemical interferences. Seventeen adult Burgundy rabbits were studied. RESULTS: Under homeostatic monitoring 'on-line' carotid blood flow (carotid BF) .changes produced by SAH in cisterna magna of 12 (plus 5 sham treated) animals were studied from the common carotid artery after external carotid artery occlusion before, during SAH up to the end of the experiments. All the animals underwent digital subtraction cerebral panangiography (CPA) after SAH obtaining a significant increase of carotid BF only when basilar vasospasm was shown by CPA. CONCLUSIONS: Carotid BF increase during basilar vasospasm was defined 'functional. monitoring' of early spasm.     

The effect of an adenosine A1 receptor agonist in the treatment of experimental subarachnoid hemorrhage-induced cerebrovasospasm

Summary Background. Adenosine is a potent vasodilator and an important modulator of cardiovascular function. It has been postulated that nitric oxide (NO) is involved in adenosine-induced vasodilation. This study was designed to examine the effect of an adenosine A₁ agonist, N⁶-cyclopentyladenosine (CPA), in the prevention of subarachnoid haemorrhage (SAH)-induced vasospasm. Method. Experimental SAH was induced in Sprague-Dawley rats by injecting 0.3 mL autogenous blood into the cisterna magna. Intraperitoneal injections of CPA (0.003 mg/kg), or vehicle were administered 5 min and 24 hours after induction of SAH. The degree of vasospasm was determined by averaging the cross sectional areas of the basilar artery 2 days after SAH. Expressions of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) in basilar artery were evaluated. Findings. There were no significant differences among the control and treated groups in physiological parameters recorded before sacrifice. When compared with animals in the control group, cross-sectional area of basilar arteries areas in the SAH only, SAH plus vehicle and SAH plus CPA groups were reduced by 19% (p < 0.01), 22% (p < 0.01), and 9% (p = 0.133), respectively. The cross-sectional areas of the CPA-treated group differed significantly from those of the SAH only and SAH plus vehicle group (p < 0.05). Induction of iNOS-mRNA and protein in basilar artery by SAH was not significantly diminished by CPA. The SAH-induced suppression of eNOS-mRNA and protein were relieved by CPA treatment. Conclusions. This is the first evidence to show an adenosine A₁ receptor agonist is effective in partially preventing SAH-induced vasospasm without significant cardiovascular complications. The mechanisms of adenosine A₁ receptor agonists in attenuating SAH-induced vasospasm may be, in part, related to preserve the normal eNOS expression after SAH. Inability in reversing the increased iNOS expression after SAH may lead to the incomplete anti-spastic effect of CPA.     

Therapeutic effects of intracarotid infusion of spermine/nitric oxide complex on cerebral vasospasm

BACKGROUND: Vasospasm is one of the underlying causes of morbidity and mortality in subarachnoid haemorrhage (SAH). The therapeutic effects of intracarotid infusion of spermine/nitric oxide complex (SPER/NO) on cerebral vasospasm in an experimental model of SAH were investigated. METHOD: Twenty-four adult male New Zealand white rabbits (2.6-3.4 kg in weight) were randomly divided into four groups (n=6), as follows: (I) control group (without SAH and drug), (II) SAH alone group (with SAH, without drug), (III) SAH placebo group (with SAH and saline), and (IV) SAH-SPER/NO group (with SAH and SPER/NO). The fresh autologous non-heparinized blood was injected into the cisterna magna to induce a SAH, after 24 hour SAH, the substance (saline or SPER/NO) was delivered to animals. All rabbits were scarified at 48-hours of induced SAH. The basilar artery with surrounding tissue was removed from the cranium and processed for paraffin embedding. Histopathological and stereological examinations of the basilar artery were done. FINDINGS: In the SPER/NO treated group of rabbits, the histopathological changes were less severe than in the SAH-alone and SAH-placebo groups. Regarding the intracarotid pressure, there was a statistically significant difference between SAH-alone and SAH-SPER/NO groups and also between SAH-SPER/NO and control groups (p<0.05). The mean cross sectional area of basilar arteries was 0.26 mm(2) in the control, whereas in SAH alone, placebo and SAH-SPER/NO groups were 0.13, 0.15 and 0.20 mm(2), respectively. INTERPRETATION: It is well known that NO is a critical substance involved in cerebral vascular dynamics. Present results indicate that treatment of vasospasm with SPER/NO in SAH may be promising. However, further studies should be done on this substance to clarify its effect on vasospasm before using the drug in clinical situations.     

Vasospasm due to massive subarachnoid haemorrhage — a rat model

Summary Although the pathophysiology of chronic cerebral vasospasm following subarachnoid haemorrhage (SAH) is still unclear, it is certain that the amount of subarachnoid blood is predictive of the severity of cerebral vasospasm. Accordingly, massive subarachnoid haemorrhage (>0.5 ml) was induced in adult rats via direct injection into the cisterna magna. Compared to other previously published models of experimental SAH in rats a much larger amount of blood was injected.The basilar artery was exposed 72 hours post subarachnoid haemorrhage and photographed under controlled conditions. The diameter of the artery was assessed by an image analyzer. A 50% reduction in diameter was found in 25 rats subjected to SAH as compared to 9 control rats and 4 rats with intracisternal saline injection.We conclude that when massive subarachnoid haemorrhage is induced, and direct measurements of the basilar artery are made, the rat can be used as a reliable model for investigation of SAH induced arterial vasospasm.     

Heat shock protein expression in cerebral vessels after subarachnoid hemorrhage

OBJECTIVE: The mechanisms of cerebral vasospasm after subarachnoid hemorrhage (SAH) remain controversial. Recent data have implicated two small heat shock proteins (HSPs), namely HSP20 and HSP27, in the regulation of vascular tone. Increases in the phosphorylation of HSP20 are associated with vasorelaxation, and increases in the phosphorylation of HSP27 are associated with impaired vasorelaxation. Therefore, we hypothesized that alterations in the expression and/or phosphorylation of these two small HSPs might play a role in cerebral vasospasm after SAH. METHODS: A rat model of endovascular perforation was used to induce SAH. Middle cerebral arteries were harvested from control animals, sham-treated animals, and animals with SAH, 48 hours after SAH induction. Dose-response curves for endothelium-independent (sodium nitroprusside, 10(-8) to 10(-4) mol/L) and endothelium-dependent (bradykinin, 10(-10) to 10(-5) mol/L) relaxing agents were recorded ex vivo. Physiological responses were correlated with the expression and phosphorylation of HSP20 and HSP27 by using one- and two-dimensional immunoblots. RESULTS: There was impaired endothelium-independent and endothelium-dependent relaxation in cerebral vessels after SAH. These changes were associated with decreased expression of both total and phosphorylated HSP20 and increases in the amount of phosphorylated HSP27. CONCLUSION: In this model, impaired relaxation of cerebral vessels after SAH was associated with increases in the amount of phosphorylated HSP27 and decreases in the expression and phosphorylation of HSP20. These data are consistent with alterations in the expression and phosphorylation of these small HSPs in other models of vasospasm.     

Nitric oxide in subarachnoid haemorrhage and its therapeutics implications

Summary Background. After the discovery that nitric oxide (NO) plays a major role in the regulation of vascular tone, this substance moved into the focus of interest with regard to vasospasm after subarachnoid haemorrhage (SAH). A multitude of interactions were discovered and some concepts of therapeutic intervention were developed. Method. The present review is based on a Medline search with the terms “nitric oxide” and “subarachnoid haemorrhage”. Findings. SAH and particularly liberated oxyhaemoglobin sequestrate the physiologically produced NO. Reactivity to NO appears to be principally preserved. As other types of injury, SAH leads to induction of inducible NO synthase (iNOS). The NO produced by this pathway cannot compensate for the lack of the physiological NO and may even lead to tissue damage by oxidative stress. Experimental therapeutic attempts use stimulation of NO production and delivery of NO donors. NO donors were also used in some small clinical trials. A final assessment of efficacy and safety is not yet possible. Conclusion. NO physiology and pathophysiology are important in the genesis of vasospasm after subarachnoid haemorrhage. NO directed therapeutic strategies enlarge the spectrum of available instruments, but complete elimination of the problem of vasospasm cannot be expected.     

The effect of very early cisternal irrigation on basilar artery spasm after SAH in the rat model

Summary The authors have investigated the effect of very early irrigation of the cerebrospinal fluid (CSF) space in the haemorrhage rat model of vasospasm. Fifteen rats had basilar cistern irrigation with physiological saline for 3 hours after subarachnoid haemorrhage (SAH), and fifteen control rats had subarachnoid haemorrhage without irrigation of clot.The changes in basilar arteries diameters were determined by angiograms obtained from the rats. The post haemorrhage angiograms showed significant basilar artery spasm in both groups (P0.0005, t-test). However in the last angiogram the basilar artery diameter was found to have the same value measured before subarachnoid haemorrhage in the irrigation group whereas no obvious change was observed in the control group. In the irrigation group the mean diameter of the basilar artery in the last angiogram was 0.412 mm. (0.30 mm to 0.50 mm). None of the animals, treated by cisternal irrigation, showed angiographic vasospasm while the latter group did (P0.0005). Animals treated with physiological saline irrigation had a median clot grade of 0.40 (range grade 0 to 2); control rats had a median grade 2.86 (range grade 1 to 4, P<0.001, Mann-Withney U test), on the brain stem, indicating significant reduction of clot by lavage.In conclusion, performance of experimental physiological saline irrigation at a very early time after subarachnoid haemorrhage prevents the arteriographic and morphological changes of both acute and late vasospasms.     

Effect of intrathecal thrombolytic therapy on subarachnoid clot and chronic vasospasm in a primate model of SAH

The safety and efficacy of the thrombolytic agent tissue-type plasminogen activator (tPA) in the elimination of subarachnoid clot and prevention of chronic vasospasm were evaluated in a blind randomized placebo-controlled trial. Twenty-four monkeys were randomly assigned to one of two groups of 12. Each group underwent baseline cerebral angiography and coagulation analysis followed by right-sided craniectomy and experimental subarachnoid hemorrhage (SAH). An Ommaya reservoir was inserted with its catheter placed into the subarachnoid space. Twenty-four hours later one group (the tPA group) received 0.5 mg of tPA in 0.5 ml of buffer injected into the reservoir every 8 hours for three doses, while the second group (the placebo group) received the same volume of normal saline. On Day 7, angiography was repeated and the animals were sacrificed. One animal from the placebo group developed a delayed ischemic neurological deficit on Day 5 after SAH. Moderate to severe vasospasm (greater than 30% reduction in vessel caliber) was present on Day 7 in the internal carotid and middle cerebral arteries of the animals in the placebo group (p less than 0.01), while in the tPA group only mild narrowing of the anterior cerebral artery was seen. No significant change in coagulation status occurred in either group. All animals in the placebo group had a large amount of subarachnoid clot remaining at the time of sacrifice, but 11 of the 12 animals in the tPA group were completely free of clot. The results of electron microscopic studies of the cerebral arteries correlated with angiography, and there was no histological evidence of brain inflammation associated with the intrathecal use of tPA.     

Attenuation of experimental subarachnoid hemorrhage--induced cerebral vasospasm by the adenosine A2A receptor agonist CGS 21680

OBJECT: Impaired endothelium-dependent relaxation is present in vasospastic cerebral vessels after subarachnoid hemorrhage (SAH) and may result from deficient production of endothelial nitric oxide synthase (eNOS) or increased production and/or activity of inducible NOS (iNOS). Accumulating evidence demonstrates that adenosine A2A receptors increase the production of NO by human and porcine arterial endothelial cells, which in turn leads to vasodilation. This study was designed to examine the effects of an adenosine A2A receptor agonist, (2(4-[2-carboxyethyl]phenyl)ethylamino)-5'-N-ethylcarboxamidoadenosine (CGS 21680), in the prevention of SAH-induced vasospasm. METHODS:. Experimental SAH was induced in Sprague-Dawley rats by injecting 0.3 ml of autologous blood into the cisterna magna of each animal. Intraperitoneal injections of CGS 21680 or vehicle were administered 5 minutes and 24 hours after induction of SAH. The degree of vasospasm was determined by averaging measurements of cross-sectional areas of the basilar artery (BA) 48 hours after SAH. Expression of eNOS and iNOS in the BA was also evaluated. Prior to perfusion-fixation, there were no significant differences among animals in the control and treated groups in any physiological parameter that was recorded. The CGS 21680 treatment significantly attenuated SAH-induced vasospasm. Induction of iNOS mRNA and protein in the BA by the SAH was significantly diminished by administration of CGS 21680. The SAH-induced suppression of eNOS mRNA and protein was also relieved by the CGS 21680 treatment. CONCLUSIONS: This is the first evidence that adenosine A2A receptor agonism is effective in preventing SAH-induced vasospasm without significant complications. The beneficial effect of adenosine A2A receptor agonists may be, at least in part, related to the prevention of augmented expression of iNOS and the preservation of normal eNOS expression following SAH. Adenosine A2A receptor agonism holds promise in the treatment of cerebral vasospasm following SAH and merits further investigation.     

Amount of subarachnoid blood and vasospasm: Current aspects

Summary Subsequent to admission after aneurysmal subarachnoid haemorrhage (SAH), 120 patients (74 women and 46 men) underwent microsurgical clipping of a total of 158 cerebral aneurysms within 96 hours after the bleed. Their mean age was 46 (20–91) years. Computed tomography (CT) findings were graded according to the modified Fisher scale and all patients had daily transcranial doppler (TCD) recordings of their basal cerebral arteries.In 19% of SAH was grade I on CT, in 44% grade II and in 37% grade III. The rate of patients who developed severe vasospasm as documented by TCD (mean blood flow velocities exceeding 160 cm/s on 2 or more consecutive days) was 39% for grade I patients, 26% for grade II patients and 34% for patients with SAH grade III on the initial CT.There was no difference in the rate of occurrence of severe vasospasm, when the patients were split into 2 groups according to the time of performance of the initial CT scan-within 24 hours, and 48–80 hours after SAH, respectively.It is concluded that the amount of subarachnoid blood on the initial CT scan should no longer be used as the indicator for occurrence and severity of the multifactorial entity vasospasm.     

The correlation between immunological reaction in the arterial wall and the time course of the development of cerebral vasospasm in a primate model

To investigate the role of immunological reactions in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH), the authors studied the correlation between immune/inflammatory reactions in the arterial wall and the time course of vasospasm in primates. Twenty monkeys were divided into four groups of 5 animals each: 1) a control group of sham-operated animals, 2) animals subjected to angiography 3 days after the induction of SAH (3-day SAH), 3) animals subjected to angiography 7 days after SAH (1-week SAH), and 4) animals subjected to angiography 7 and 14 days after SAH (2-week SAH). To induce SAH, the main cerebral arteries on the right were dissected free of the arachnoid, and an autologous blood clot was placed around the arteries. To evaluate vasospasm, all animals underwent a baseline angiogram before SAH; angiography was repeated at different intervals in each group, as outlined above. Histopathological changes and the deposition of the immunoglobulin IgG in the arterial wall were evaluated immunohistochemically in each group. The cerebral arteries on the side of the clot showed evidence of mild vasospasm (-24.6% reduction) on the angiogram performed on Day 3, severe vasospasm (-51.7%) on Day 7, and mild vasospasm (-12.8%) on Day 14. The infiltration of inflammatory cells was most marked in the spastic arterial wall in the 1-week SAH group. In the 2-week SAH group, severe myonecrosis and intimal disruption were observed, even in the vessels that showed only mild vasospasm, and the inflammatory reactions had almost abated.(ABSTRACT TRUNCATED AT 250 WORDS)     

The role of constitutive and inducible nitric oxide synthase in the human brain after subarachnoid hemorrhage

AIM: Results of prior experimental studies show that nitric oxide (NO) plays an important role in the pathogenesis of vasospasm. In the present study, the expression of endothelial NO synthase (eNOS), neuronal NO synthase (nNOS) and of inducible NO synthase (iNOS) in the human brain after subarachnoid haemorrhage were studied. METHODS: Twenty-three samples of gyrus rectus or temporal operculum that were obtained during a surgical approach to anterior circulation aneurysms were used for this study. Seven samples were obtained during surgery from patients who underwent operation for unruptured aneurysms (control group). eNOS-mRNA, nNOS-mRNA and iNOS-mRNA were extracted and amplified by RT-PCR. Patients were subdivided for intergroup comparison by: age < 60 / > 60 years; source of sample; clinical grading; extent of subarachnoid clot; presence of intracerebral/intraventricular hematoma; surgical timing; vasospasm; outcome. RESULTS: There was a significant increase in the expression of eNOS between SAH and control groups (P=0.046); eNOS hyperexpression was higher in the patients in poor clinical conditions (P=0.002) and lasted until the late phase of haemorrhage. nNOS overall expression was unchanged but hyperexpression was observed in the patients in poor clinical conditions (P=0.008). There was a significant hyperexpression of iNOS in SAH group (P=0.026), and in patients with vasospasm (P=0.0024); the expression was significantly reduced in the late phase of haemorrhage (P=0.0038). CONCLUSIONS: The acute decrease of NO after SAH is not determined by reduced constitutive NOS expression and iNOS induction is a consequence of SAH and plays a major role in the pathogenesis of vasospasm.     

Time course of the blood-arterial wall barrier disruption following experimental subarachnoid haemorrhage

Summary The time course of the blood-arterial wall barrier disruption following experimental subarachnoid haemorrhage (SAH) was studied in 24 rabbits. Animals with SAH received two successive blood injections through the cisterna magna. Horseradish peroxidase (HRP) was given intravenously 30 minutes before sacrifice to assess the integrity of the barrier. In the basilar arteries taken from animals that were sacrificed 4 days after the first SAH, HRP-reaction products were diffusely observed in the subendothelial space. Three weeks following the first SAH, permeation of HRP was still observed in half of the animals. However, in animals sacrificed 7 weeks after the first SAH, no permeation of HRP into the subendothelial space was noted. Opening of the interendothelial space seemed to be the major mechanism for HRP permeation into the subendothelial space rather than transendothelial vesicular transport. Disruption of the bloodarterial wall barrier in the major cerebral arteries following SAH may play a role in the pathogenesis of vasospasm.     

A study of the effectiveness of the iron-chelating agent deferoxamine as vasospasm prophylaxis in a rabbit model of subarachnoid hemorrhage

The pathogenesis of cerebral vasospasm occurring after subarachnoid hemorrhage (SAH) is unknown. Several lines of experimentation have suggested a free radical mechanism in the etiology of vasospasm. Iron is an important catalyst in the generation of free radicals and lipid peroxides in response to tissue injury. We hypothesize that the elaboration of iron from the subarachnoid clot might result in enhanced generation of free radicals and lipid peroxidation. If so, then treatment with deferoxamine, an iron-chelating compound, might reduce the formation of free radicals and thereby ameliorate vasospasm. This hypothesis was examined in a rabbit model of experimental cerebral vasospasm. New Zealand White rabbits were divided into the following experimental groups: control (normal) animals (n = 7), control animals treated with deferoxamine (n = 3), animals subjected to SAH and killed on Day 2 (n = 7), animals subjected to SAH on Day 2 and treated with deferoxamine (n = 9), animals subjected to SAH killed on Day 3 (n = 7), and animals subjected to SAH on Day 3 and treated with deferoxamine (n = 7). Deferoxamine treatment (50 mg/kg/8 hours) was begun 16 hours before the induction of SAH and continued until the animals were killed by perfusion fixation. The basilar artery caliber was assessed using morphometric techniques. The diameter of the basilar arteries in the control animals was 0.64 +/- 0.02 mm. Deferoxamine treatment alone did not alter the artery diameter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevention of cerebral vasospasm by a capsaicin derivative, glyceryl nonivamide, in an experimental model of subarachnoid hemorrhage

BACKGROUND: Cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) remains a major complication in patients suffering from SAH. In our previous study, we reported that stimulating vascular K(+) channel activity prevented the development of cerebral vasospasm. Recent evidence indicates that glyceryl nonivamide (GLNVA), a capsaicin derivative, has a vasorelaxant effect on the aortic vascular smooth muscle due to the release of coronary calcitonin gene-related peptide, which in turn stimulates K(+) channel opening. The purpose of the present study was to examine the preventive effects of GLNVA on vasospasm. METHODS: New Zealand white rabbits were subjected to experimental SAH by injecting autologous blood into the cisterna magna. GLNVA or vehicle was injected intrathecally immediately after the induction of SAH. All animals were killed by perfusion-fixation at 48 hours after SAH. The basilar arteries were removed and sectioned, and their cross-sectional areas were measured. RESULTS: The average cross-sectional areas of basilar arteries were reduced by 69% and 71% in the SAH only and SAH plus vehicle groups, respectively, when compared with the healthy controls. After treatment with 0.35, 1.75, and 3.5 mg/kg GLNVA in rabbits subjected to SAH the average cross-sectional area was decreased by 46%, 12% and 2%, respectively, when compared with the healthy controls. The protective effect of GLNVA achieved statistical significance at all dosages. Morphologically, corrugation of the internal elastic lamina of vessels was often observed in the vehicle-treated group, but was not prominent in the GLNVA-treated groups or healthy controls. CONCLUSION: The findings showed that GLNVA dose-dependently attenuated cerebral vasospasm after SAH in the rabbit. These results suggest that intrathecal administration of GLNVA could be an effective strategy for preventing cerebral vasospasm after SAH.     

Inducible nitric oxide synthase: a possible key factor in the pathogenesis of chronic vasospasm after experimental subarachnoid hemorrhage.

OBJECT: The role of nitric oxide (NO) in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH) is not well understood. Nitric oxide is a well-established vasodilatory substance; however, in SAH, NO may become a major source for the production of injurious free-radical species, leading to chronic cerebral vasospasm. Reactive overproduction of NO to counteract vascular narrowing might potentiate the detrimental effects of NO. The focus of the present study is to determine the extent of reactive induction of inducible nitric oxide synthase (iNOS) after experimental SAH. METHODS: Chronic vasospasm was induced in male Wistar rats by an injection of autologous blood (100 microl) into the cisterna magna followed by a second injection 24 hours later. A control group of 10 animals was treated with injections of 0.9% sodium chloride solution. Vasospasm was verified by pressure-controlled angiography after retrograde cannulation of the external carotid artery 7 days later. In 11 of 15 animals radiographic evidence of cerebral vasospasm was seen. The animals were perfusion fixed and their brains were removed for immunohistochemical assessment. With the aid of a microscope, staining for iNOS was quantified in 40-microm floating coronal sections. Immunohistochemical staining for iNOS was markedly more intense in animals with significant angiographic evidence of vasospasm. Virtually no staining was observed in control animals. Seven days after the second experimental SAH, labeling of iNOS was found in endothelial cells, in vascular smooth-muscle cells, and, above all, in adventitial cells. Some immunohistochemical staining of iNOS was observed in rod cells (activated microglia), in glial networks, and in neurons. CONCLUSIONS: The present study demonstrates induction of iNOS after experimental SAH.     

Inhibition of cerebral vasospasm by intracranial delivery of ibuprofen from a controlled-release polymer in a rabbit model of subarachnoid hemorrhage

OBJECT: Leukocyte-endothelial cell interactions may play a role in the development of cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) because the extravasation of circulating leukocytes into the periadventitial space within 24 hours after the hemorrhage appears to be a critical event in this process. Ibuprofen is an antiinflammatory agent that inhibits the expression of specific cell adhesion molecules and, consequently, disrupts leukocyte-endothelial cell interactions. The authors investigated the efficacy of ibuprofen delivered locally from controlled-release polymers in the rabbit basilar artery (BA) model of cerebral vasospasm. METHODS: Ibuprofen was incorporated into controlled-release ethylene-vinyl acetate copolymer (EVAc) constituting 45% of the resulting polymer by weight. Fifty-four New Zealand White rabbits were randomized to 10 groups: sham operation (seven animals); SAH only (seven animals); and SAH plus either empty EVAc or ibuprofen-EVAc polymer at 30 minutes or 6, 12, or 24 hours (five animals per group; 40 total). The rabbits were killed 72 hours after induction of SAH, at the time of maximal vasospasm. The efficacy of ibuprofen in preventing vasospasm was assessed by measuring lumen patency of the rabbit's BAs. The intracranial controlled release of ibuprofen resulted in a significant inhibition of vasospasm when treatment was initiated at 30 minutes (patency 92.3 +/- 5.1% compared with 52.1 +/- 5.1% in animals given empty EVAc; p < 0.001) and 6 hours (patency 69.5 +/- 3.5% compared with 47.2 +/- 1.5% in animals given empty EVAc; p < 0.03) after blood deposition compared with treatment with empty EVAc. No effect was observed when treatment was begun at either 12 or 24 hours. CONCLUSIONS: Local intracranial delivery of ibuprofen accomplished using controlled-release polymers prevents vasospasm in the rabbit BA model of vasospasm when administered within 6 hours after blood exposure.