The role of active smooth-muscle contraction in the occurrence of chronic vasospasm in the canine two-hemorrhage model

Pharmacologic Management of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) remains a condition with suboptimal functional outcomes, especially in the young population. Pharmacotherapy has an accepted role in several aspects of the disease and an emerging role in several others. No preventive pharmacologic interventions for SAH currently exist. Antiplatelet medications as well as anticoagulation have been used to prevent thromboembolic events after endovascular coiling. However, the main focus of pharmacologic treatment of SAH is the prevention of delayed cerebral ischemia (DCI). Currently the only evidence-based medical intervention is nimodipine. Other calcium channel blockers have been evaluated without convincing efficacy. Anti-inflammatory drugs such as statins have demonstrated early potential; however, they failed to provide significant evidence for the use in preventing DCI. Similar findings have been reported for magnesium, which showed potential in experimental studies and a phase 2 trial. Clazosentane, a potent endothelin receptor antagonist, did not translate to improve functional outcomes. Various other neuroprotective agents have been used to prevent DCI; however, the results have been, at best inconclusive. The prevention of DCI and improvement in functional outcome remain the goals of pharmacotherapy after the culprit lesion has been treated in aneurysmal SAH. Therefore, further research to elucidate the exact mechanisms by which DCI is propagated is clearly needed. In this article, we review the current pharmacologic approaches that have been evaluated in SAH and highlight the areas in which further research is needed.

Antioxidants: The new frontier for translational research in cerebroprotection

It is important for the anesthesiologist to understand the etiology of free radical damage and how free-radical scavengers attenuate this, so that this knowledge can be applied to diverse neuro-pathological conditions. This review will concentrate on the role of reactive species of oxygen in the pathophysiology of organ dysfunction, specifically sub arachnoid hemorrhage (SAH), traumatic brain injury (TBI) as well as global central nervous system (CNS) hypoxic, ischemic and reperfusion states. We enumerate potential therapeutic modalities that are been currently investigated and of interest for future trials. Antioxidants are perhaps the next frontier of translational research, especially in neuro-anesthesiology.

Effect of a free radical scavenger, edaravone, on free radical reactions: related signal transduction and cerebral vasospasm in the rabbit subarachnoid hemorrhage model

OBJECTIVE

it is hypothesized that free radical reactions evoked by oxyhemoglobin (oxyHb) cause cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH), even though the detailed mechanisms have not yet been fully established. The aims of this study were thus to investigate, through the use of the double-hemorrhage rabbit model, the possibility that free radical reactions play a role in cerebral vasospasm and to delineate the mechanism of signal transduction that causes cerebral vasospasm.

METHODS

in the SAH group, SAH was simulated using the double-hemorrhage rabbit model. In the treatment group, edaravone (0.6 mg/kg), a potent free radical scavenger, was injected into the central ear vein twice a day. Four days after SAH, the basilar artery was excised. The degree of cerebral vasospasm was evaluated by measuring the diameter of each basilar artery, and the expression of Rho-kinase in the vascular wall was examined by western blotting.

RESULTS

the diameter of the basilar artery in the edaravone-treated group was 0.64 ± 0.06 mm, which was statistically significantly larger than that in the nontreated SAH group (0.50 ± 0.03 mm; p < 0.01). The expression of Rho-kinase in the edaravone-treated group was statistically significantly reduced in comparison to that of the nontreated SAH group.

CONCLUSION

results from this study have indicated for the first time that free radical reactions mediated by oxyHb may play an important role in the pathogenesis of cerebral vasospasm through the expression of Rho-kinase.

Tirilazad for aneurysmal subarachnoid haemorrhage

BACKGROUND

Delayed cerebral ischaemia is a significant contributor to poor outcome (death or disability) in patients with aneurysmal subarachnoid haemorrhage (SAH). Tirilazad is considered to have neuroprotective properties in animal models of acute cerebral ischaemia.

OBJECTIVES

To assess the efficacy and safety of tirilazad in patients with aneurysmal SAH.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched October 2009); the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 2, 2009); MEDLINE (1966 to October 2009); EMBASE (1980 to October 2009); and the Stroke Trials Directory, the National Center for Complementary and Alternative Medicine, and the National Institute of Health Clinical Trials Database (searched October 2009). We handsearched 10 Chinese journals, searched the reference lists of relevant publications, and contacted the manufacturers of tirilazad.

SELECTION CRITERIA

Randomised trials of tirilazad started within four days of SAH onset, compared with placebo or open control in patients with aneurysmal SAH documented by angiography and computerised tomography (CT) scan or cerebrospinal fluid examination, or both.

DATA COLLECTION AND ANALYSIS

We extracted data relating to case fatality, poor outcome (death, vegetative state, or severe disability), delayed cerebral ischaemia (or symptomatic vasospasm), cerebral infarction and adverse events of treatments. We pooled the data using the Peto fixed-effect method for dichotomous data.

MAIN RESULTS

We included five double-blind, placebo-controlled trials involving 3821 patients; there was no significant heterogeneity. Oral or intravenous nimodipine was used routinely as a background treatment in both groups in all trials. There was no significant difference between the two groups at the end of follow up for the primary outcome, death (odds ratio (OR) 0.89, 95% confidence interval (CI) 0.74 to 1.06), or in poor outcome (death, vegetative state or severe disability) (OR 1.04, 95% CI 0.90 to 1.21). During the treatment period, fewer patients developed delayed cerebral ischaemia in the tirilazad group than in the control group (OR 0.80, 95% CI 0.69 to 0.93). Subgroup analyses did not demonstrate any significant difference in effects of tirilazad on clinical outcomes. Leukocytosis and prolongation of Q-T interval occurred significantly more frequently in the treatment group in only one trial evaluating tirilazad at high dose. There was no significant difference in infusion site disorders or other laboratory parameters between the two groups.

AUTHORS' CONCLUSIONS

There is no evidence that tirilazad, in addition to nimodipine, reduces mortality or improves poor outcome in patients with aneurysmal SAH.

Effect of a free radical scavenger, edaravone, in the treatment of patients with aneurysmal subarachnoid hemorrhage

OBJECTIVE

It is hypothesized that cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH) is induced by free radicals released from a subarachnoid clot. This study therefore investigated the effect of a new free radical scavenger, edaravone, in the treatment of patients with aneurysmal SAH.

METHODS

Ninety-one patients with aneurysmal SAH participated in this study and were randomized into a control group (n = 42) and an edaravone-treated group (n = 49). The difference between the 2 groups in terms of incidence of delayed ischemic neurological deficits (DINDs) and cerebral infarction caused by vasospasm, and Glasgow Outcome Scale score at 3 months after SAH were statistically analyzed.

RESULTS

The incidence of DINDs was 21% in the control group and 10% in the edaravone-treated group, yet there was no statistically significant difference between the 2 groups (P = 0.118). In patients with DINDs, the incidence of cerebral infarction caused by vasospasm was 66% in the control group and 0% in the edaravone-treated group (P = 0.028), whereas the incidence of poor outcome caused by vasospasm was 71% in the control group and 0% in the edaravone-treated group (P = 0.046).

CONCLUSION

We found a trend toward a lesser incidence of DINDs and a lesser incidence of poor outcome caused by cerebral vasospasm in edaravone-treated patients. It might therefore be suggested that edaravone is a useful agent for the treatment of aneurysmal SAH.

A postmarketing surveillance study of fasudil treatment after aneurysmal subarachnoid hemorrhage

BACKGROUND

The aim of the present study was, first, to assess safety of fasudil (Eril; Asahi Kasei Pharma Corp, Tokyo, Japan) and, second, to investigate whether the effects of fasudil in the phase 3 trial could be reproduced in a PMS study.

METHODS

Between 1995 and 2000, a total of 1462 patients met the eligibility criteria of the phase 3 trial and were treated with fasudil in a PMS study. Adverse events, low-density areas on CT scans, symptomatic vasospasm, and clinical outcome were all recorded. The results were compared with those in the phase 3 trial. Patients with Fisher grade 3 on admission were selected (subgroup), and the results were also compared with those in the phase 3 trial.

RESULTS

The occurrence of adverse events, including intracranial bleeding and hypotension, low-density areas, and clinical outcomes were similar between the fasudil-treated patients in the phase 3 trial and the patients in the PMS study. The absence of symptomatic vasospasm was more common in the PMS study than in the phase 3 trial. Of the 1462 patients, 842 met the criteria for the subgroup. In the subgroup, the occurrence of low-density areas, the absence of symptomatic vasospasm, and clinical outcomes were similar between the fasudil-treated patients in the phase 3 trial and the patients in the PMS study.

CONCLUSIONS

The present PMS study described the tolerability, safety, and efficacy of fasudil in a large number of patients undergoing surgery for SAH, as demonstrated previously in the phase 3 trial.

Contribution of the remodeling response to cerebral vasospasm

The authors review the remodeling response of blood vessels that occurs after various injuries to arteries. The role of this response in vasospasm after subarachnoid hemorrhage (SAH) is reviewed. There is some evidence that cerebral arteries remodel after SAH in that they are less compliant and contractile than normal. Evidence for other features, such as alteration of smooth muscle phenotype, proliferation of cells and synthesis of extracellular matrix, is conflicting and requires a further study. A remodeling response probably contributes to vasospasm but the magnitude of its importance, in relation to smooth muscle contraction, which also occurs, also needs to be further defined.

Endovascular Management of Cerebral Vasospasm

CEREBRAL VASOSPASM REMAINS a leading cause of death and disability in patients with ruptured cerebral aneurysms. The development of endovascular intervention in the past two decades has shown promising results in the treatment of vasospasm. Endovascular techniques that have been used in humans include intra-arterial infusion of vasorelaxants and direct mechanical dilation with transluminal balloon angioplasty. This article reviews the current indications and role of endovascular therapy in the management of cerebral vasospasm, its clinical significance, and potential future therapies.

Calcium sensitivity of vasospastic basilar artery after experimental subarachnoid hemorrhage

Arteries that develop vasospasm after subarachnoid hemorrhage (SAH) may have altered contractility and compliance. Whether these changes are due to alterations in the smooth muscle cells or the arterial wall extracellular matrix is unknown. This study elucidated the location of such changes and determined the calcium sensitivity of vasospastic arteries. Dogs were placed under general anesthesia and underwent creation of SAH using the double-hemorrhage model. Vasospasm was assessed by angiography performed before and 4, 7, or 21 days after SAH. Basilar arteries were excised from SAH or control dogs ( n = 8–52 arterial rings from 2–9 dogs per measurement) and studied under isometric tension in vitro before and after permeabilization of smooth muscle with α-toxin. Endothelium was removed from all arteries. Vasospastic arteries demonstrated significantly reduced contractility to KCl with a shift in the EC50toward reduced sensitivity to KCl 4 and 7 days after SAH ( P < 0.05, ANOVA). There was reduced compliance that persisted after permeabilization ( P < 0.05, ANOVA). Calcium sensitivity was decreased during vasospasm 4 and 7 days after SAH, as assessed in permeabilized arteries and in those contracted with BAY K 8644 in the presence of different concentrations of extracellular calcium ( P < 0.05, ANOVA). Depolymerization of actin with cytochalasin D abolished contractions to KCl but failed to alter arterial compliance. In conclusion, it is shown for the first time that calcium sensitivity is decreased during vasospasm after SAH in dogs, suggesting that other mechanisms are involved in maintaining the contraction. Reduced compliance seems to be due to an alteration in the arterial wall extracellullar matrix rather than the smooth muscle cells themselves because it cannot be alleviated by depolymerization of smooth muscle actin.

Time course of the diameter of the major cerebral arteries after subarachnoid hemorrhage using corrosion cast technique

In this report, we examined whether corrosion cast method is also applicable for the measurement and estimation of the rat major arteries in which subarachnoid hemorrhage (SAH) is produced. Additionally, we have examined the diameters of the rat major arteries following SAH. A total of 0.3 ml autologous blood was injected into the cisterna magna of male Sprague-Dawley rats for the SAH model. A perfusion of a semi-polymerized casting medium was performed, 10 min, 30 min, 1 h, 4 h, 8 h, 1 day, 2 days, 3 days, 5 days, and 7 days after SAH. The brains were corroded in a 10% NaOH solution. The BA and the other major arteries were then measured using scanning electron microscopy (SEM). Macroscopic observation and hematoxylin-eosin (HE) staining were also performed. Using the corrosion cast method, the biphasic contractile response was observed in the BA; 8.3% and 11.6% contractions were observed 30 min and 1 day after SAH, respectively. In addition, there was almost no smooth muscle or adventitial thickening in the chronic stage. In contrast, the dilative response was observed in the internal carotid artery and middle cerebral artery 10 min after SAH. Macroscopic findings and HE staining revealed that the extensive basal subarachnoid hematoma had almost disappeared by day 2. These results indicate that in this model, the minimal spasm, which occurs one day after SAH, can be explained by the small capacity of the rat subarachnoid space and the rapid cerebrospinal fluid washout around major vessels at the cerebral base. Moreover, the present data also show the compensatory dilatation in the ICA and MCA in the early stage after SAH.

Antioxidant therapy against cerebral vasospasm following aneurysmal subarachnoid hemorrhage

1. Approximately one-third of the morbidity and mortality due to aneurysmal subarachnoid hemorrhage (SAH) is caused by delayed ischemic neurological deficit (DIND) due to cerebral vasospasm. 2. Compared to prolonged arterial constriction in other parts of the body, cerebral vasospasm is characterized by its long duration and refractoriness to vasodilators such as calcium antagonists. 3. Whereas oxyhemoglobin (oxyHb) liberated into the CSF from the subarachnoid clot has been deemed the causative agent of vasoconstriction, the biochemical mechanisms whereby oxyHb elicits prolonged constriction of the cerebral arteries has remained elusive. Here, we suggest that oxyHb triggers the generation of reactive oxygen intermediates (ROI) within the CSF. 4. Multiple lines of evidence indicate that the occurrence of vasospasm, namely, prolonged smooth muscle contraction, is due to the following intracellular events. 5. First, hydroxyl radicals (OH*), the most reactive species of ROI, are generated within the cerebral arterial wall via the Fenton and Haber-Weiss reactions catalyzed by oxyHb. Second, subsequent peroxidative membrane damage in the arterial smooth muscle cell enhances the metabolism of phosphatidylcholine and phosphatidylethanolamine, leading to a rise in the intracellular level of diacylglycerol, an endogenous activator of protein kinase C. 6. The prolonged arterial contraction that occurs during vasospasm is attributable primarily to the activation of protein kinase C, not to the Ca2+/calmodulin system. In this article, literature relevant to the above thesis is reviewed, and the rationale for the antioxidant therapy against cerebral vasospasm is discussed.

Subarachnoid haemorrhage: what happens to the cerebral arteries?

1. Subarachnoid haemorrhage (SAH) is a unique disorder and a major clinical problem that most commonly occurs when an aneurysm in a cerebral artery ruptures, leading to bleeding and clot formation. Subarachnoid haemorrhage results in death or severe disability of 50-70% of victims and is the cause of up to 10% of all strokes. Delayed cerebral vasospasm, which is the most critical clinical complication that occurs after SAH, seems to be associated with both impaired dilator and increased constrictor mechanisms in cerebral arteries. Mechanisms contributing to development of vasospasm and abnormal reactivity of cerebral arteries after SAH have been intensively investigated in recent years. In the present review we focus on recent advances in our knowledge of the roles of nitric oxide (NO) and cGMP, endothelin (ET), protein kinase C (PKC) and potassium channels as they relate to SAH. 2. Nitric oxide is produced by the endothelium and is an important regulator of cerebral vascular tone by tonically maintaining the vasculature in a dilated state. Endothelial injury after SAH may interfere with NO production and lead to vasoconstriction and impaired responses to endothelium-dependent vasodilators. Inactivation of NO by oxyhaemoglobin or superoxide from erythrocytes may also occur in the subarachnoid space after SAH. 3. Nitric oxide stimulates activity of soluble guanylate cyclase in vascular muscle, leading to intracellular generation of cGMP and relaxation. Subarachnoid haemorrhage appears to cause impaired activity of soluble guanylate cyclase, resulting in reduced basal levels of cGMP in cerebral vessels and often decreased responsiveness of cerebral arteries to NO. 4. Endothelin is a potent, long-lasting vasoconstrictor that may contribute to the spasm of cerebral arteries after SAH. Endothelin is present in increased levels in the cerebrospinal fluid of SAH patients. Pharmacological inhibition of ET synthesis or of ET receptors has been reported to attenuate cerebral vasospasm. Production of and vasoconstriction by ET may be due, in part, to the decreased activity of NO and formation of cGMP. 5. Protein kinase C is an important enzyme involved in the contraction of vascular muscle in response to several agonists, including ET. Activity of PKC appears to be increased in cerebral arteries after SAH, indicating that PKC may be critical in the development of cerebral vasospasm. Recent evidence suggests that PKC activation may occur in cerebral arteries after SAH as a result of decreased negative feedback influence of NO/cGMP. 6. Cerebral arteries are depolarized after SAH, possibly due to decreased activity of potassium channels in vascular muscle. Decreased basal activation of potassium channels may be due to several mechanisms, including impaired activity of NO (and/or cGMP) or increased activity of PKC. Vasodilator drugs that produce hyperpolarization, such as potassium channel openers, appear to be unusually effective in cerebral arteries after SAH. 7. Thus, endothelial damage and reduced activity of NO may contribute to cerebral vascular dysfunction after SAH. Potassium channels may represent an important therapeutic target for the treatment of cerebral vasospasm after SAH.

Augmentation of both hemolysate-induced contraction and activation of protein kinase C by submaximum activation in canine cerebral arteries in vitro

Although phorbol esters, synthetic activators of protein kinase C (PKC), can stimulate large increases in the binding of cytosolic PKC to form membrane-bound PKC (PKCm, an indicator of PKC activation), the authors report that even small increases in PKCm induced by phorbol esters (8-12% of total PKC content) can be associated with significant PKC-mediated contractions in vitro (50-85% of maximum) in normal canine cerebral arteries. Increases in PKCm of similarly small magnitude were found in vitro when control artery segments were exposed to hemolysate, but only if the arterial smooth-muscle cells were first slightly depolarized by increased extracellular potassium to values of membrane potential similar to those observed in canine cerebral arteries during chronic cerebral vasospasm. These increases in PKCm (6-8% of total PKC content) coincided with a greatly augmented contractile response to hemolysate. These results show that the previous observation of only a small increase in PKCm (approximately 7% of total PKC content) after experimental subarachnoid hemorrhage in the canine model does not preclude a potentially important role for PKC-mediated contraction in the pathogenesis of cerebral vasospasm.

Three-dimensional analysis of vasospastic major cerebral arteries in rats with the corrosion cast technique

BACKGROUND AND PURPOSE

Although mice, rats, and other small animals are commonly used for molecular biology research, their use in the evaluation of cerebral vasospasm after subarachnoid hemorrhage is somewhat problematic because of the correspondingly small size of their cerebral vessels. We have already reported that the corrosion cast technique was useful for evaluating newly formed cerebral vessels in neural grafts in these small animals. In the present study we applied the corrosion cast technique to the evaluation of hemolysate-induced cerebral vasospasm in rats and performed three-dimensional analysis for comparison. The casting was done 10 minutes after the hemolysate injection, so that only acute "vasospasm" was assessed.

METHODS

After withdrawal of 0.1 mL cerebrospinal fluid, 0.2 mL hemolysate (n = 9) or saline (n = 10) was injected into the cisterna magna of male Sprague-Dawley rats weighing between 300 and 350 g. Ten minutes later, perfusion of a semipolymerized casting medium was performed at an injection pressure of 100 to 120 mm Hg. The brains were immersed and corroded in 10% NaOH solution. After these procedures, the basilar artery as well as peripheral vessels was analyzed morphologically with scanning electron microscopy. Conventional histological analysis with the use of paraffin-embedded section with hematoxylin-eosin staining was also performed, and the results were compared with those for the corrosion cast methods.

RESULTS

In the saline-injected group, SEM showed that the inner surface of the basilar artery was smooth and the form of the endothelial cell was printed on the surface of the cast. In the hemolysate-injected group, the basilar artery showed an apparent vasospasm over its entire length, and corrugation was observed on the inner surface of the basilar artery in a three-dimensional fashion. Higher magnification revealed that the nuclei of the endothelial cells were distorted. Local narrowing of the basilar artery and vasospasm in the arteries of the anterior circulation and in peripheral arteries were also observed. Measurement of the inner diameter of the basilar artery showed 37.8% contraction in the hemolysate-injected group compared with the saline-injected group by the corrosion cast method. This degree of vasospasm was similar to that observed by the conventional histological method.

CONCLUSIONS

In this report we show that detailed three-dimensional observation in the rat can be performed qualitatively and quantitatively with the corrosion cast technique. We conclude that this method derives an accurate measurement of the diameter of rat major cerebral arteries and is more reliable for analyzing vasospasm in rats than angiography and other conventional procedures.

The effect of endovascular therapy for cerebral arterial spasm, its limitation and pitfalls

PURPOSE

The effect of endovascular treatment for vasospasm was investigated by analysing the results of patients treated in Wakayama City in 1994.

MATERIALS AND METHODS

Ninety nine patients with ruptured cerebral aneurysms, who survived more than one week and were treated in Wakayama City in 1994, were studied. Twenty five patients caused symptomatic vasospasm and 25 were treated by endovascular therapy, percutaneous transluminal angioplasty (PTA) and/or intra-arterial papaverine infusion (IAP). PTA was performed for proximal vasospasm which located in the main arterial trunk, such as ICA, M1, BA (n = 3). IAP was chosen for distal vasospasm which located mainly in the M2, A1, A2 (n = 12). PTA and/or IAP was performed for diffuse vasospasm which located in proximal and distal arteries (n = 10).

RESULTS

In the proximal vasospasm group, all patients were good to moderately disabled on the Glasgow outcome scale (GOS). In the distal vasospasm group, 8 patients were good to moderately disabled, and 4 patients were severely disabled. The overall results were as follows: 17 (68%), good to moderately disabled, 4 (16%), severely disabled, 4 (16%), dead. The morbidity and mortality rate was 8/25 (32%) in symptomatic spasm group.

CONCLUSION

PTA was very effective especially for proximal vasospasm, but IAP was not always effective for distal or diffuse vasospasm. Diffuse vasospasm revealed a high mortality rate in spite of the endovascular therapy.

Protein kinase C has two different major roles in lattice compaction enhanced by cerebrospinal fluid from patients with subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Compaction of extracellular matrix (ECM) lattices by cultured fibroblasts was accelerated by cerebrospinal fluid (CSF) from patients with subarachnoid hemorrhage (SAH). The rate of acceleration was significantly related to the clinical grade of vasospasm. However, the mechanism remains unclear. Evidence exists for an important role in cerebral vasospasm for protein kinase C (PKC). The purpose of this study was to help clarify whether PKC has a role in contraction of the ECM.

METHODS

We studied the effects of a myristoylated PKC peptide inhibitor (Myr-Arg-Phe-Ala-Arg-Lys-Gly-Ala-Leu-Arg-Gln-Lys-Asn-Val) (PKC peptide inhibitor), (5-isoquinolinesulfonyl)-homopiperazine (HA-1077) (inhibitor of protein kinase A, myosin light-chain kinase, and protein kinase G), 7-deacetyl-6-(N-ace-tylglycyl)-forskolin (forskolin) (adenyl cyclase activator), and diacylglycerol-lactone (DAG-lactone) (PKC activator) on fibroblast-populated collagen lattice compaction with or without CSF from SAH patients. Four sets of fibroblasts were used: three explanted from skin and one from cerebral artery.

RESULTS

Moderate and high concentrations of PKC peptide inhibitor inhibited lattice compaction with or without acceleration by CSF. Low concentration of PKC peptide inhibitor enhanced acceleration by CSF but had no effects without CSF. HA-1077 could not inhibit lattice compaction. Forskolin inhibited compaction. DAG-lactone accelerated compaction in early phases.

CONCLUSIONS

In the mechanism of acceleration of contraction of ECM under the influence of CSF, PKC seems to have two different roles. Protein kinase A and myosin light-chain kinase apparently play more minor roles than PKC in the mechanism, but no evidence was found of a role for protein kinase G activation in matrix compaction.

Development of calcitonin gene-related peptide slow-release tablet implanted in CSF space for prevention of cerebral vasospasm after experimental subarachnoid haemorrhage

The calcitonin gene-related peptide (CGRP), a known potent intrinsic cerebral vasodilator, is contained in the sensory nerves from trigeminal ganglia that inervate the cerebral arteries. We previously reported that human alpha CGRP (hCGRP) dilates spastic cerebral arteries after experimental subarachnoid haemorrhage (SAH) in rabbits. In the present study, we investigated the prophylactic potential of a sustained higher cerebrospinal fluid level of hCGRP against experimental cerebral vasospasm. An hCGRP slow-release tablet (hCGRP s-r tablet) was developed for cisternal implantation. Experimental SAH was induced by percutaneous cisternal injection of autologous arterial blood. Angiography was initiated on day 1 (before SAH) and performed everyday. The hCGRP s-r tablet was implanted into the cisterna magna on day 2 in the treated groups. The spastic response of the basilar artery was maximized on day 4 in the non-treated (80.7% of day 1) and the placebo-treated (79.3%) groups. In contrast, the arterial diameters on day 4 were 96.1% and 90.5% of day 1 in the groups implanted with hCGRP 24 micrograms and 153 micrograms s-r tablets, respectively. We also measured the concentration of hCGRP in the cerebrospinal fluid (CSF) following implantation of the hCGRP 24 micrograms s-r tablet in the cisterna magna. The hCGRP concentration before implantation was below the dectable level. Following implantation, the hCGRP level in the CSF was 23.12 nmol/L on the second day and remained at elevated levels until the fifth day. These experiments suggest that the intrathecal single implantation of the hCGRP s-r tablet could produce an elevated concentration of hCGRP in the CSF over five days and have prevented the cerebral vasospasm after SAH in the rabbit. The hCGRP s-r tablet may be clinically applicable in the treatment of patients with SAH against cerebral vasospasm.

Role of extracellular Ca2+ in subarachnoid hemorrhage-induced spasm of the rabbit basilar artery

BACKGROUND AND PURPOSE

The role of extracellular Ca2+ in the maintenance of chronic vasospasm after subarachnoid hemorrhage (SAH) is largely unknown. Indeed, studies thus far have been limited to demonstrations that L-type Ca(2+)-channel antagonists were unable to reverse the spasm. This study tested whether SAH-induced vasospasm is maintained, at least in part. through the influx of extracellular Ca2+ and whether the influx of extracellular Ca2+ occurs through L-type Ca2+ channels and possibly, in addition, through store operated channels (SOCs). Furthermore, as there is considerable evidence in the literature to suggest that the spasm is mediated through endothelin-1 (ET-1) release, we tested whether the Ca2+ dependency of the spasm was consistent with the mediation of the spasm by ET-1.

METHODS

Chronic spasm of the basilar artery was induced in a double SAH rabbit model. Relaxation of SAH-, ET-1-, serotonin-, and KC1-constricted basilar artery in response to Ca(2+)-free solution, verapamil, and Ni2+ was measured in situ with the use of a cranial window.

RESULTS

SAH induced 23% constriction of the basilar artery. Ca(2+)-free solution and 1 mumol/L verapamil reversed the constriction of SAH vessels by 60% and 17%, respectively. In contrast, control vessels challenged with 40 to 50 mmol/L KCl, which induced 34% constriction, relaxed in response to Ca(2+)-free solution and verapamil by 98% and 89%, respectively. In SAH vessels, verapamil followed by 0.1 mmol/L Ni2+, which is known to block SOCs, induced a combined relaxation of 67%. Control vessels challenged with 3 nmol/L ET-1, which induced a magnitude of constriction similar to that of SAH (29%), relaxed in response to Ca(2+)-free solution, verapamil, and verapamil plus Ni2+ by 69%, 20%, and 50%, respectively (P > .05) versus respective values in SAH vessels). In contrast, control vessels challenged with 2 to 8 mumol/L serotonin, which induced a magnitude of constriction similar to those of SAH and ET-1 (22%), completely relaxed in response to Ca(2+)-free solution and verapamil.

CONCLUSIONS

These results demonstrate that the maintenance of chronic spasm in the two-hemorrhage rabbit model after SAH is due to smooth muscle cell contractile mechanisms partly dependent on the influx of extracellular Ca2+. The influx of extracellular Ca2+ results from the opening of L-type Ca2+ channels and an additional channel or channels. We speculate that the L-type Ca2+ channel-independent influx of extracellular Ca2+ results from the opening of SOCs. The Ca(2+)-dependent characteristics of the spasm likely reflect the mediation of the spasm by ET-1.

Effects of a hydroxyl radical scavenger on delayed ischemic neurological deficits following aneurysmal subarachnoid hemorrhage: results of a multicenter, placebo-controlled double-blind trial

A water-soluble, novel synthetic compound, AVS ((+/-)-N, N'-propylenedinicotinamide; nicaraven) has no demonstrable vasoactive properties but scavenges hydroxyl radicals in aqueous environmental conditions at neutral pH. Based on the results of preceding experimental and clinical studies showing marked ameliorative effects of AVS on cerebral vasospasm and ischemic brain damage, a multicenter, placebo-controlled double-blind clinical trial was undertaken to verify its beneficial effects on delayed ischemic neurological deficits (DINDs) due to vasospasm and on the overall outcome of patients with subarachnoid hemorrhage (SAH). A total of 162 patients with SAH who had Glasgow Coma Scale scores between 7 and 15 on admission were enrolled in the trial. Drug administration (4 g AVS or 4 g glucose as placebo; infused intravenously for 6-8 hours once a day) was begun within 5 days post-SAH and continued for 10 to 14 days. Intent-to-treat analysis of these patients revealed that the overall incidence of DINDs, which was defined as an exacerbation of impaired consciousness and/or focal neurological deficits, was significantly reduced, by 34.5% (placebo 54.2%, AVS 35.5%; p < 0.05, Mann-Whitney U-test). The Glasgow Outcome Scale (GOS) score at 1 month was significantly improved by AVS (p < 0.05, U-test). At 3 months, the difference in the GOS scores between the groups became marginal on U-tests (p < 0.10), but the percentage of good outcome tended to increase, with a relative increase of 20.3% (AVS 76.3%, placebo 63.4%; p < 0.10, chi-square test), and the cumulative incidence of death was significantly reduced (p < 0.05, log-rank test). No significant adverse reaction attributable to treatment was observed. the usefulness of AVS in therapy for SAH is strongly indicated by the fact that the agent significantly ameliorated DINDs, leading to a marked improvement in the GOS scores at 1 month, as well as a reduction in the cumulative incidence of death by 3 months.

Intracellular calcium, myosin light chain phosphorylation, and contractile force in experimental cerebral vasospasm

It remains unknown what proportion of delayed arterial narrowing after subarachnoid hemorrhage depends on ongoing metabolic activity within arterial smooth muscle cells versus changes in the passive structural properties of the arterial wall. To determine this, vasospasm was induced by the double subarachnoid hemorrhage model. Anterior spinal artery segments were harvested from control dogs and from dogs with vasospasm. The segments were suspended in a force transducer and stretched to an optimal length for contraction. The difference in tension between 37 and 0 degrees C was defined as the intrinsic tone, and the residual tension at 0 degrees C was defined as the passive tension. The segments taken from dogs with vasospasm had increased intrinsic tone and passive tension (the differences were 3.8 kN/m2 [P < 0.05] and 14.8 kN/m2 [P < 0.025], respectively). Hence, the passive component accounted for 79.6% of the increased tension in vasospastic arterial segments. The intracellular calcium concentration was measured in these segments, using the luminescent calcium indicator, aequorin. The vasospastic segments had increased basal intracellular calcium concentration (398 versus 258 nmol/L, P < 0.025). In parallel experiments, control and vasospastic vessels were immediately excised when the animals were killed, and the vessels were quick-frozen. Subsequently, using two-dimensional gel electrophoresis to measure percent myosin light chain phosphorylation, vasospastic vessels were found to have increased myosin light chain phosphorylation (37 versus 2%, P < 0.05). The increased intracellular calcium concentration and increased percent myosin light chain phosphorylation in vasospastic segments implicate a role for the Ca(2+)-dependent pathway of smooth muscle cell contraction in vasospasm.

Relaxation of subarachnoid hemorrhage-induced spasm of rabbit basilar artery by the K+ channel activator cromakalim

BACKGROUND AND PURPOSE

Cerebral vasospasm resulting from subarachnoid hemorrhage (SAH) is refractory to most vasodilators. However, despite evidence that a mechanism underlying the vasospasm may be smooth muscle cell membrane depolarization resulting from decreased K+ conductance, the ability of K+ channel activators to relax the spasm has not been thoroughly investigated. The purpose of this study, therefore, was to investigate whether K+ channel activation selectively relaxes SAH-induced vasospasm.

METHODS

Three days after SAH in the rabbit, relaxation of the basilar artery in response to the K+ channel activator cromakalim as well as to staurosporine (protein kinase C antagonist), forskolin (adenylate cyclase activator), and sodium nitroprusside (guanylate cyclase activator) was measured in situ with the use of a cranial window. Relaxation in response to these agents was also investigated in control vessels contracted with serotonin. Membrane potential of the smooth muscle cells of the basilar artery from SAH and control rabbit was measured in vitro with the use of intracellular microelectrodes.

RESULTS

Cromakalim completely relaxed the SAH-induced spastic basilar artery, while staurosporine, forskolin, and sodium nitroprusside were significantly less efficacious. In contrast, sodium nitroprusside and forskolin were more efficacious relaxants in serotonin-contracted control vessels than in SAH vessels. The K+ channel blocker glyburide and high [K+] prevented cromakalim-induced relaxation. Glyburide did not inhibit forskolin-induced relaxation of serotonin-contracted control vessels. Cromakalim concentration-dependently repolarized spastic basilar artery smooth muscle cells, and the repolarization was prevented by glyburide.

CONCLUSIONS

These results suggest that K+ channel activation selectively relaxes SAH-induced vasospasm. We speculate that the ability of K+ channel activators to selectively relax the spasm may be due, at least in part, to the underlying inhibition of K+ channels after SAH.

Papaverine-sensitive vasospasm and arterial contractility and compliance after subarachnoid hemorrhage in dogs

This study examined the relationship between papaverine-sensitive and -insensitive components of vasospasm, arterial contractility and compliance, and time after subarachnoid hemorrhage (SAH) in dogs. Eighteen dogs underwent angiography and then two intracisternal injections of blood. Angiography was repeated 4 (n = 5), 7 (n = 4), 10 (n = 4), or 14 (n = 5) days later. Papaverine, 100 to 200 mg, was infused into the basilar artery, and angiography was repeated. Four additional dogs had cerebral angiography only and served as controls. The basilar arteries were removed and studied pharmacologically. Significant vasospasm of the basilar artery was observed each time after SAH. Papaverine significantly reversed vasospasm at 4 and 7 days (88 +/- 6% and 63 +/- 11% of vasospasm reversed; analysis of variance, P < 0.05). The papaverine-insensitive component of vasospasm increased significantly with increasing time after SAH and with increasing severity of vasospasm. Arterial contractility and compliance decreased significantly with increasing time after SAH and were significantly related to the degree of papaverine-insensitive vasospasm but not to the severity of vasospasm. In conclusion, the majority of vasospasm early after SAH in dogs was caused by reversible vasoconstriction. The ability of papaverine to reverse vasospasm depended on the time after SAH and on the severity of vasospasm, a finding that may be important to the use of papaverine in humans. The pathological and biochemical basis for the association between papaverine-insensitive vasospasm and reduced arterial wall contractility and compliance remains to be determined.

Effects of new 21-aminosteroid tirilazad mesylate (U74006F) on chronic cerebral vasospasm in a "two-hemorrhage" model of beagle dogs

The present work aimed at examining the effect of tirilazad mesylate (U74006F), a newly developed lipid peroxidation inhibitor, on the intraluminal narrowing of basilar artery subjected to subarachnoid hemorrhage (SAH) in beagle dogs. In Experiment 1, an intravenous bolus injection of either vehicle or U74006F (0.5, 1.5 and 3.0 mg/kg) was repeated every 8 hours after an induction of the first SAH until the animals were killed. A dose of 0.5 mg/kg of U74006F provided the greatest beneficial effect. In Experiment 2, an intravenous infusion of 100 ml of saline containing either vehicle or U74006F (0.3 and 1.0 mg/kg) was given in the same time schedule as in Experiment 1. Post-SAH treatment of U74006F, at a dosage of approximately 0.5 mg/kg, showed a beneficial effect by infusion as well as by bolus administration. The present study demonstrates that U74006F has an ability to prevent chronic vasospasm in the canine SAH model.

The effect of Nicorandil on chronic cerebral vasospasm

The present study is aimed at examining the therapeutic effect of Nicorandil on chronic vasospasm using beagle dogs subjected to a "two-haemorrhage" insult, as well as its dilatory effect on the PDA [phorbol-12,13 diacetate]-induced contraction of the canine basilar artery. 1. A total of 12 animals of either sex, weighing 7 to 12 kg, were assigned into saline control and Nicorandil-treated groups. Immediately after the second induction of subarachnoid haemorrhage (SAH), animals started to receive the agent via the venous route at the constant rate of 10 micrograms/kg/minute for six hours (day 3). On days 4, 5, and 6, the drug was given twice at the same rate for three hours. After the final angiograms, animals were sacrificed by exsanguination. 2. Using ring specimen of the canine basilar artery at a resting tension of 3 g, isometric tension was monitored to examine the effect of Nicorandil on PDA induced contraction. Nicorandil significantly ameliorated chronic vasospasm and inhibited PDA-induced contraction in a dose-dependent fashion. The present data indicate that Nicorandil provides a useful way of treating chronic vasospasm after SAH.