Subarachnoid Hemorrhage In Rabbits Research Articles

COX-2, Another Important Player in the Nitric Oxide–Endothelin Cross-Talk

See related article, pages 1439–1445 Traditionally, the role of the endothelium was thought to be primarily that of a selective barrier to the diffusion of macromolecules from the vessel lumen to the interstitial space. During the past 20 years, numerous additional roles for the endothelium have been defined such as regulation of vascular tone, modulation of inflammation, promotion as well as inhibition of vascular growth, and modulation of platelet aggregation and coagulation. Endothelial dysfunction is a characteristic feature of patients with cardiovascular risk factors such as hypercholesterolemia, hypertension, diabetes mellitus, and chronic smoking. More recent studies indicate that it may predict long-term atherosclerotic disease progression as well as cardiovascular event rate.1 There is a growing body of evidence that decreased endothelial bioavailability of nitric oxide (NO·) in particular attributable to increased production of reactive oxygen species, such as superoxide (O2·−), leads to an activation of the renin–angiotensin system,2,3 increased formation of cyclooxygenase (COX)-dependent vasoconstrictors,4 but also to increased expression of the most potent endogenous vasoconstrictor endothelin-1 (ET-1).5–9 Of the 4 active endothelins (ET-1 to ET-4) ET-1 is the predominant isoform in the cardiovascular system. ET-1 exerts its major cardiovascular effects through activation of 2 distinct G protein–coupled receptors, the ETA and ETB receptors. ETA receptors are found exclusively in smooth muscle cells. Endothelin-1 promotes vasoconstriction, mitogenesis, and thrombosis predominantly via binding to the ETA receptor. ETB receptors are localized to some extent in smooth muscle cells, but also in endothelial cells. Activation of ETB receptors has been demonstrated to cause the release of NO· and prostacyclin (PGI2).10,11 In normal states with p reserved vascular (endothelial) NO …

Systemic Administration of Simvastatin after the Onset of Experimental Subarachnoid Hemorrhage Attenuates Cerebral Vasospasm

Experimental evidence suggests that intercellular adhesion molecule-1 mediated leukocyte extravasation contributes to the pathogenesis of cerebral vasospasm. Simvastatin, an HMG-CoA reductase inhibitor, decreases intercellular adhesion molecule-1 expression and competitively inhibits leukocyte intercellular adhesion molecule-1 binding. We hypothesized that administration of simvastatin after the onset of subarachnoid hemorrhage (SAH) would attenuate perivascular granulocyte migration and ameliorate cerebral vasospasm in a rabbit model of SAH. New Zealand white rabbits (n = 15) underwent injection of autologous blood into the cisterna magna or sham surgery followed by subcutaneous injection of simvastatin (40 mg/kg) or vehicle 30 minutes, 24 hours, and 48 hours after SAH or sham surgery. Seventy-two hours later, basilar artery lumen diameter was measured by in situ perfusion/fixation and image analysis. CD-18 monoclonal antibody stained perivascular granulocytes and macrophages were counted under light microscopy. In vehicle treated rabbits, mean +/- standard deviation basilar artery diameter was reduced 3 days after SAH (n = 5) versus sham (n = 5) rabbits (0.49 +/- 0.08 mm versus 0.75 +/- 0.03 mm, P < 0.01). After SAH, mean +/- standard deviation basilar artery diameter was greater in simvastatin (n = 5) treated rabbits versus vehicle (n = 5) (0.63 +/- 0.04 mm versus 0.49 +/- 0.08 mm, P < 0.01). In vehicle treated rabbits, SAH resulted in an increase in the mean +/- standard deviation perivascular CD18 cell count (sham-vehicle, 2.8 +/- 2; SAH-vehicle 90 +/- 27; P < 0.01). Subcutaneous administration of simvastatin attenuated this increase in perivascular CD18-positive cells after SAH (SAH statin, 41.6 +/- 13; SAH vehicle, 90 +/- 27; P < 0.001). Subcutaneous administration of simvastatin after the onset of SAH attenuates perivascular granulocyte migration and ameliorates basilar artery vasospasm after experimental SAH in rabbits. 5-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, such as simvastatin, may potentially serve as agents in the prevention of cerebral vasospasm after SAH.

Inhibitory effect of deuterium oxide on cerebral vasospasm after experimental subarachnoid hemorrhage in a rabbit model

Object: We wished to determine the inhibitory effect of deuterium oxide (D2O) on cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH).Methods and results: An established rabbit single-hemorrhage was used. Thirty-five rabbits were randomly divided into four groups: non-treatment, sham control, lower-D2O, and higher-D2O treatment groups. Angiography was performed before (day 0) and after (day 2) SAH and the CVS ratio was calculated by comparing the diameter of the basilar artery (BA) on day 2 with that on day 0. After death, blood clot volume was assessed and the BA was dissected from the brain for histological examination. The CVS ratio in D2O-treatment groups was significantly higher in comparison with that in non-treatment and sham control groups (p < 0.0001). Furthermore, the volume of blood clot around the BA was reduced significantly in D2O-treatment groups, compared with those in both the non-treatment and the sham control groups (p < 0.05). Histological examination showed that the BA represented less folding of the internal elastic lumina in D2O-treatment groups, while a corrugation of the intima with the thickened vessel wall was seen in both the non-treatment and sham control groups.Conclusion: Therapeutic administration of D2O into the cisterna magna exhibited an inhibitory effect on CVS after SAH in rabbits.

Prevention of vasospasm by anti-CD11/CD18 monoclonal antibody therapy following subarachnoid hemorrhage in rabbits.

Adhesion of leukocytes and their migration into the periadventitial space may be critical in the pathophysiology of vasospasm following subarachnoid hemorrhage (SAH). The cell adhesion molecules involved in this process are lymphocyte function-associated antigen-1 (CD11a/CD18) and macrophage antigen-1 (CD11b/CD18), which are present on neutrophils/macrophages, and intercellular adhesion molecule-1 (CD54), which is present in endothelial cells. A humanized monoclonal antibody (mAb), Hu23F2G, targets CD11/CD18 and prevents leukocyte adhesion to endothelial cells. In this study, systemic administration of Hu23F2G prevented vasospasm in the rabbit model of SAH. Twenty-six New Zealand White rabbits were injected with autologous blood into the cisterna magna to induce SAH, after which they were randomized to receive injections of either Hu23F2G (10 animals) or a placebo at 30 minutes and 24 and 48 hours after SAH (six animals). Control animals underwent sham operations (four animals) or SAH alone (six animals). The animals were killed 72 hours after SAH, their bodies perfused and fixed, and their basilar arteries processed for morphometric analysis. Peripheral white blood cells (WBCs) were counted at 72 hours. The percentages of lumen patency were compared using the Student t-test. The presence of neutrophils and macrophages was confirmed by immunohistochemical analysis in which a rat anti-rabbit anti-CD18 mAb and cresyl violet were used. Treatment with Hu23F2G resulted in the significant prevention of vasospasm. Animals treated with Hu23F2G had 90 +/- 7% lumen patency compared with 65 +/- 7% in the placebo group (p = 0.025). The percentage of lumen patency in the SAH-only group was 59 +/- 10%. The mean WBC count was 16,300 +/- 2710/microl in the treatment group, compared with 7000 +/- 386/microl in the control group (p = 0.02). Administration of Hu23F2G produced increased numbers of WBCs in 70% of the animals treated. This study supports the concept that leukocyte-endothelial cell interactions play an important role in the pathophysiology of chronic vasospasm after SAH. Systemic therapy with an anti-CD11/CD18 mAb prevents vasospasm after SAH by inhibiting adhesion of neutrophils and macrophages and their migration into the periadventitial space.

Pharmacokinetics of controlled-release polymers in the subarachnoid space after subarachnoid hemorrhage in rabbits.

Implantation of controlled-release polymers into the subarachnoid space to deliver drugs for treatment of vasospasm after subarachnoid hemorrhage (SAH) is currently of interest. Among the issues regarding local delivery of drugs in the subarachnoid space, however, are the extent of diffusion and the rate of release of the loaded agents. In this study Evans blue dye (EBD) was loaded into controlled-release polymers and its pharmacokinetic properties were determined in vitro and in vivo by using a rabbit model of SAH. Ethylene-vinyl acetate copolymer (EVAc) was loaded 40% (w:w) with EBD and its pharmacokinetics were spectrophotometrically determined in vitro by examining three EBD-EVAc polymers. Additional polymers were implanted either into the frontal lobe or into the cisterna magna of 16 New Zealand White rabbits. Subarachnoid hemorrhage was induced in eight of the animals by an injection of 1.5 ml of arterial blood into the cisterna magna. The animals were killed 3 or 14 days postoperatively, their brains and spinal cords were harvested, and samples of each were placed in formamide for dye extraction and quantification. Specimens were examined macroscopically and the concentrations of EBD were determined with the aid of a spectrophotometer. The EBD-EVAc polymers continuously released EBD over a 133-day period. The controlled release of the dye into the subarachnoid space in either location resulted in staining of the entire central nervous system (CNS) in rabbits when the polymers were placed either on the frontal lobe or in the cisterna magna. The EBD diffusion covered a distance of at least 40 cm. The presence of blood in the subarachnoid space did not interfere with the diffusion. In this study the authors define the rate and extent of diffusion of EBD from controlled-release polymers placed in the subarachnoid space under conditions of SAH. Evans blue dye diffused through the entire rabbit CNS, covering a distance greater than that of the longest dimension of the hemicircumference of the subarachnoid space around the human brain. The pharmacokinetic properties of EBD-EVAc polymers are comparable to those of antivasospasm agents that are successfully used in animal models of SAH.

The effects of niguldipine pretreatment on cerebral vasospasm after subarachnoid haemorrhage in rabbits

AbstractSeveral different mechanisms contribute to the pathogenesis of cerebral vasospasm after subarachnoid haemorrhage. Whatever these mechanisms are, the vessel contraction is ultimately induced by an increase of free intracellular Ca2+ in the arterial wall. In this study, we investigated the effect on cerebral blood flow of a new dihydropyridine derivative Ca‐channel blocker Niguldipine, in a rabbit experimental cerebral vasospasm model. The cerebral blood flow was significantly decreased in the saline treatment group when compared with control group. Niguldipine pretreatment caused a significant increase in cerebral blood flow. This effect should be investigated further.

Effects of thrombin inhibitor on thrombin-related signal transduction and cerebral vasospasm in the rabbit subarachnoid hemorrhage model.

Thrombin is activated in the cerebrospinal fluid (CSF) after a subarachnoid hemorrhage (SAH). However, the relationship between thrombin and cerebral vasospasm has not yet been fully established. The aim of this study was to investigate the possibility of thrombin as a causative factor for cerebral vasospasm and to delineate the signal transduction mechanism that results in thrombin-inducing sustained vasoconstriction in cerebral vasospasm. In the SAH group, SAH was simulated by the 2-hemorrhage rabbit model. In the treatment group, antithrombin III (AT-III) was injected into the cisterna magna just before production of the SAH. CSF samples were obtained serially to measure d-dimer with latex photometric immunoassay. On day 4, the basilar artery was excised after perfusion-fixation. The degree of cerebral vasospasm was evaluated by measuring the cross-sectional area of each basilar arterial lumen, and the expression of mitogen-activated protein kinase (MAPK) in the vascular wall was examined with an immunohistochemical technique. In the treatment group, the value of d-dimer on day 4 was 0.83+/-0.07 microg/mL, which was statistically significantly lower than that in the nontreated SAH group (2.49+/-0.09 microg/mL, P<0.01). The cross-sectional area of the arterial lumen in the treatment group was 3.67x10(5)+/-1.58x10(4) square pixels, which was statistically significantly larger than that in the nontreated SAH group (2.60x10(5)+/-2.29x10(4) square pixels; P<0.01). MAPK was detected diffusely in the vascular smooth muscle cell layer in the nontreated SAH group, but it was absent in the treatment group. Inhibition of thrombin activity leads to amelioration of cerebral vasospasm and suppression of MAPK diphosphorylation. This suggests that thrombin and its related signal transduction, including the MAPK cascade, appear to play an important role in the pathogenesis of cerebral vasospasm after SAH.

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Attenuation of cerebral vasospasm in rabbits using clonidine hydrochloride, a central adrenergic agonist

The aim of this study was to assess, firstly, if exclusion of central noradrenergic areas in the hypothalamus and brain stem with the central sympathetic blocker clonidine hydrochloride could prevent the development of chronic vasospasm following experimental subarachnoid haemorrhage in rabbits and, secondly, if, parallel with the effect on cerebral arteries, changes in dopamine β-hydroxylase concentration in the hypothalamus and brain stem could also be detected. Experimental subarachnoid haemorrhage, in concentrations of 1 ml of autologous arterial blood/1 kg of body weight was carried out on 18 New Zealand rabbits. Histological specimens were obtained by the method of perfusion fixation after the rabbits were sacrificed on day 8 after subarachnoid haemorrhage. The spastic effect of experimentally induced subarachnoid haemorrhage was determined by assessing the intensity of corrugation of the intima of the rabbit basilar artery by the previously developed method of corrugation coefficient and computer image analysis. The concentration and localization of dopamine β-hydroxylase in noradrenaline-containing neurons was immunohistochemically assessed (semiquantitatively as 0, 1 and 2) with anti-dopamine β-hydroxylase, at precisely defined sites of the hypothalamus and brain stem of the same rabbit. The results revealed less corrugated and smoother intima in the basilar artery and significantly lower dopamine β-hydroxylase concentration in the control group of rabbits with sham subarachnoid haemorrhage and without any additional interventions (mean corrugation coefficient=1.123±0.024, P=0.35×10 −3; mean dopamine β-hydroxylase=0.350±0.071, P=0.22×10 −3), and smoother intima in the basilar artery with significantly lower concentration of dopamine β-hydroxylase in the clonidine group (rabbits with subarachnoid haemorrhage and central α 2-blocker clonidine hydrochloride at a daily dose of 0.03 mg/kg of body weight for 8 days; mean corrugation coefficient=1.177±0.058, P=1.7×10 −3; mean dopamine β-hydroxylase=0.583±0.175, P=1.1×10 −3). In comparison, the haemorrhage only group (rabbits with subarachnoid haemorrhage and without medication; mean corrugation coefficient=1.370±0.101; mean dopamine β-hydroxylase=1.214±0.313) displayed intensive corrugation of the intima of the basilar artery and a significantly more intensive accumulation of dopamine β-hydroxylase than did the control group and the clonidine group. The results of this study demonstrated that the central α 2-blocker clonidine hydrochloride effectively prevents vasospasm, and diminishes the concentration of cerebral dopamine β-hydroxylase in the hypothalamus and brain stem after experimental subarachnoid haemorrhage in rabbits.

Oral administration of an inhibitor of endothelin-converting enzyme attenuates cerebral vasospasm following experimental subarachnoid haemorrhage in rabbits.

Increasing evidence has implicated endothelin-1 (ET-1), a potent vasoconstrictive peptide, in the pathophysiology of cerebral vasospasm after subarachnoid haemorrhage (SAH). Endothelin-converting enzyme-1 (ECE-1), the protease involved in the final step of post-translational processing of ET-1, cleaves the inactive precursor big ET-1 at the Trp(21)-Val (22) peptide bond. In our previous study, we found that an inhibitor of ECE-1, CGS 26303, could prevent and reverse the arterial narrowing after SAH in rabbits. CGS 26393, a prodrug of CGS 26303, is an orally active, long-acting inhibitor of ECE-1. The present study examined the effects of CGS 26393 on the prevention and reversal of cerebral vasospasm after SAH. New Zealand white rabbits were subjected to experimental SAH by injecting autologous blood into the cisterna magna. In the prevention study, the drug was given orally 1 h before the induction of SAH. All drug treatments in the reversal study were initiated at 23 h after induction of SAH. One of three dosages (3, 10 or 30 mg/kg) of CGS 26393 or vehicle was administrated orally twice daily, and all animals were sacrificed by perfusion and fixation 48 h after SAH. Basilar arteries were removed and sectioned, and cross-sectional areas were measured. Cerebrospinal fluid (CSF) was collected prior to perfusion. Oral administration of CGS 26393 attenuated SAH-induced cerebral vasospasm in a dose-dependent manner in both the prevention and reversal groups. These effects achieved statistical significance at all dosages when compared with the SAH-only or SAH plus vehicle groups. Moreover, the attenuation of vasospasm following oral administration of CGS 26393 was more efficacious than that obtained with bolus injections of CGS 26303. The levels of free CGS 26303 in the CSF were increased in a dose-dependent manner in all three CGS 26393-treated groups. This study provides the first evidence that oral administration of an inhibitor of ECE-1, CGS 26393, is capable of preventing and reversing cerebral vasospasm following SAH. These findings also reinforce evidence demonstrating that treatment with an ECE-1 inhibitor is a potentially viable therapeutic approach for reducing cerebral vasospasm after SAH.

Beneficial effects of systemic administration of recombinant human erythropoietin in rabbits subjected to subarachnoid hemorrhage.

Cerebral vasospasm and ischemic damage are important causes of mortality and morbidity in patients affected by aneurysmal subarachnoid hemorrhage (SAH). Recently, i.p. administration of recombinant human erythropoietin (r-Hu-EPO) has been shown to exert a neuroprotective effect during experimental SAH. The present study was conducted to evaluate further the effect of r-Hu-EPO administration after SAH in rabbits on neurological outcome, degree of basilar artery spasm, and magnitude of neuronal ischemic damage. Experimental animals were divided into six groups: group 1 (n = 8), control; group 2 (n = 8), control plus placebo; group 3 (n = 8), control plus r-Hu-EPO; group 4 (n = 8), SAH; group 5 (n = 8), SAH plus placebo; group 6 (n = 8), SAH plus r-Hu-EPO. r-Hu-EPO, at a dose of 1,000 units/kg, and placebo were injected i.p. starting 5 min after inducing SAH and followed by clinical and pathological assessment 72 h later. Systemic administration of r-Hu-EPO produced significant increases in cerebrospinal fluid EPO concentrations (P < 0.001), and reduced vasoconstriction of the basilar artery (P < 0.05), ischemic neuronal damage (P < 0.001), and subsequent neurological deterioration (P < 0.05). These observations suggest that r-Hu-EPO may provide an effective treatment to reduce the post-SAH morbidity.

Effects of aging on cerebral vasospasm after subarachnoid hemorrhage in rabbits.

The effects of aging on cerebral vasospasm after subarachnoid hemorrhage (SAH) remain to be elucidated. The aim of this study was to clarify age-related differences of vasospasm and of papaverine reactivity in the responses of basilar arteries after SAH in rabbits. Rabbits receiving a single injection of arterial blood into the cisterna magna were divided into 3 groups: young (2 to 3 months old), adult (6 to 9 months old), and old (20 to 40 months old). Vertebrobasilar angiograms were obtained before SAH and 1, 2, 4, and 7 days after SAH. Papaverine was administrated selectively via the vertebral artery on day 2, and serial angiography was performed for up to 2 hours. Vessel structures were assessed with light microscopy on days 1, 2, 4, and 7 after SAH and at 10, 30, and 60 minutes after papaverine infusion. Mortality from SAH in old rabbits was 40%, whereas that of young and adult rabbits was 0%. Angiograms revealed that SAH induced maximal constriction of the basilar arteries on day 2 in all age groups, and the constrictions were significantly increased with age at all time points investigated. The degree of dilatation of spastic basilar arteries after intra-arterial papaverine administration significantly decreased with age. Duration of the efficacy of papaverine became significantly shorter with age. Vessel diameter returned to the preinfusion value approximately 120, 60, and 30 minutes after infusion in young, adult, and old rabbits, respectively. Light microscopy in old rabbits showed luminal narrowing and corrugation of the internal elastic lamina not only in the basilar arteries but also in small arteries and intraparenchymal arterioles. This study suggests that aging increases the degree of vasospasm in rabbits. The impaired reactivity to papaverine with aging might imply the early transition of the aged vessel to the papaverine-resistant chronic stage.

Inhibition of poly(ADP-ribose) polymerase attenuates cerebral vasospasm after subarachnoid hemorrhage in rabbits.

Poly(ADP-ribose) polymerase (PARP) is important in modulating inflammation, which has been implicated in cerebral vasospasm after subarachnoid hemorrhage (SAH). We investigated the role of PARP in vasospasm using 3-aminobenzamide (3-AB), a PARP inhibitor, in a rabbit model. Twenty-four New Zealand White rabbits were divided into 4 groups: (1) no treatment (control group, n=6); (2) blood injection without pretreatment (SAH-only group, n=6); (3) blood injection with pretreatment by vehicle (SAH+vehicle group, n=6); and (4) blood injection with pretreatment by 3-AB (SAH+3-AB group, n=6). We used the single-hemorrhage model of SAH, injecting autologous arterial blood into the cisterna magna. Angiography was performed before (baseline) and after (day 2) SAH, and the diameter of the basilar artery (BA) was measured. Animals were euthanatized after the second angiogram. After perfusion and fixation, the brains were cut into sections for hematoxylin and eosin and immunohistochemical staining for poly(ADP-ribosyl)ation. In the control group, there were no differences in the BA lumen caliber between baseline and day 2 (96.8+/-10.4%). Cerebral vasospasm in the SAH+3-AB group (88.2+/-6. 2%) was remarkably attenuated in comparison with that in the SAH-only group (64.9+/-8.0%) and the SAH+vehicle group (65.6+/-10. 8%). The BA in the SAH+3-AB group showed less corrugation of the tunica elastica interna than that in the SAH-only and SAH+vehicle groups. Staining for poly(ADP-ribosyl)ation was markedly inhibited in smooth muscle and adventitial cells of the BA in the SAH+3-AB group compared with other groups. Inhibiting ADP-ribosylation attenuates cerebral vasospasm after SAH in rabbits, and PARP activation may play an important role in the development of cerebral vasospasm.

The effect of sympathetic nervous system exclusion on cerebral vasospasm following subarachnoid hemorrhage in rabbits.

The mechanisms of vasospasm after subarachnoid hemorrhage (SAH) are still not fully known. Most likely, local factors mediated by blood extravasation from the ruptured aneurysm under arterial pressure into the subarachnoid space are involved [10]. However, evidence that vasospasm is manifested both in extra- and intracranial arteries after SAH indicates that other factors might be involved in the patophysi-ology of vasospasm [3]. It is certain that, in the majority of cases, the most intensive vasospasm occurs near the largest blood collection in the subarachnoid space. However, it may also develop in cerebral vessels in other parts of the subarachnoid space in which CT reveals no blood, and even in extracranial arteries. Thus, local as well as systemic mechanisms appear to exist. Such a mechanism could be the stimulation of the sympathetic nervous system (SNS) that occurs in conjunction with SAH. The hypothesis that the SNS could be involved in vasospasm is not new and has never been thoroughly refuted [1, 4, 5].

Effective improvement of the cerebral vasospasm after subarachnoid hemorrhage with low-dose nitroglycerin.

In the rabbit subarachnoid hemorrhage (SAH) model, the sensitivity of spastic basilar arteries to nitric oxide (NO) was enhanced whereas the endothelial function to release/produce NO became impaired, as described previously. We assumed from these results that low-dose NO might selectively dilate spastic arteries without influencing normal or systemic blood vessels; therefore, we investigated whether exogenous low-dose NO effectively improves cerebral vasospasm. Low-dose NO was derived from a small size of the tape containing nitroglycerin, which is not invasive and is clinically available. The experimental SAH was induced by injecting autologous blood into the cisterna magna of the rabbit. Experiments were performed on the following three groups: (a) SAH group with nitroglycerin tape (nitroglycerin group), (b) SAH group with placebo tape (placebo group), and (c) saline group injected with saline instead of blood. The tape containing 0.675 mg nitroglycerin was applied once daily for 2 days onto the skin area of the rabbit's ear. Angiograms were performed once before cisternal injection of blood and/or saline and again on day 2. On day 2 the basilar artery was isolated and sliced into 2-mm ring preparations. Relaxations of the basilar artery to acetylcholine, sodium nitroprusside, and calcium ionophore A23187, as well as the contractile responses to serotonin and endothelin- 1, were measured. The diameter of the basilar artery on day 2 was reduced to 69.6+/-2.2% (n = 7) before the injection of autologous blood. The angiographic vasospasm of the basilar artery was partially but significantly (p<0.0001) improved to the percentage diameter of 89.4+/-1.4% (n = 7) by the application of low-dose nitroglycerin, which did not affect the systemic blood pressure and heart rate. In the basilar artery preparations harvested from SAH rabbits on day 2, the impaired acetylcholine-induced endothelium-dependent relaxation was partially but significantly (p<0.001) improved in the nitroglycerin group. However, this group remained unaffected in the increased sensitivity to nitroglycerin and the contractile responses to serotonin and endothelin-1. Low-dose nitroglycerin tape effectively improved the cerebral vasospasm after SAH without any significant changes in the systemic circulation and would be one of the useful and noninvasive treatments for cerebral vasospasm. The results seem to be partially affected by the effective dilation of the spastic artery and the improvement of the impaired endothelium-dependent relaxation with low-dose NO.

Confocal microscopic evidence of decreased alpha-actin expression within rabbit cerebral artery smooth muscle cells after subarachnoid haemorrhage.

Our objective was to determine whether subarachnoid haemorrhage modifies cerebral artery smooth muscle cell phenotype and the contractile protein alpha-actin measured 7 days after haemorrhage. We used a rabbit subarachnoid haemorrhage model and immunofluorescence labelling of alpha-smooth muscle actin, vimentin and desmin. The paired comparison between the haemorrhage and sham rabbits was performed using confocal laser-scanning microscopy. We found in the haemorrhage group significantly less intense alpha-actin immunostaining (p = 0.036) and more intense vimentin immunostaining (p = 0.043) but no significant change in the intensity of desmin staining. Our results indicate an absolute decrease after subarachnoid haemorrhage in the amount of functional alpha-actin and in the light of the literature may suggest a certain degree of dedifferentiation of smooth muscle cells in the cerebral artery wall.

Attenuation of basilar artery spasm after experimental subarachnoid hemorrhage in rabbit by potassium channel activator cromakalim--a preliminary result.

Cerebral vasospasm associated with aneurysmal subarachnoid hemorrhage (SAH) remains a major complication in patients suffering from SAH. Regulation of membrane potential of arterial smooth muscle through activation or inhibition of potassium (K+) channel activity provides an important mechanism to dilate or constrict arteries. The present study examined the effect of a K+ channel activator, cromakalim, on cerebral vasospasm following experimental SAH. By the route of topical application and intra-arterial injection, basilar arteries were exposed transclivally and measured on-line using videomicroscopic camera. Continuous microinjection from right vertebral artery was given after the result of application was observed. Basilar artery spasm induced by SAH was released by topical or intra-arterial administration of cromakalim, and this beneficial effect against cerebral vasospasm was dose-dependent. There was no significant difference between topical and intra-arterial administration of cromakalim. These results indicate that K+ channel activator may play an important role for ameliorating cerebral vasospasm. An important goal of future studies will be to carefully evaluate the possibility and effect of intra-arterial administration of cromakalim to treat angiographic vasospasm.

Anticardiolipin antibody aggravates cerebral vasospasm after subarachnoid hemorrhage in rabbits.

We previously reported that patients with antiphospholipid antibodies (aPLs) frequently demonstrate cerebral infarction due to cerebral vasospasm after subarachnoid hemorrhage (SAH). To examine the participation of aPLs in the pathogenesis of vasospasm after SAH, we studied the relationships of aPLs and SAH in an animal model. SAH was produced in 34 rabbits that received two subarachnoid injections of autologous arterial blood. The animals were divided into four experimental groups: SAH was induced in group A (n=9), intracutaneous injection of cardiolipin (CL) was performed before the induction of SAH in group B (n=5), intravenous injection of CL was performed before SAH in group C (n=12), and cyclosporin A was infused intravenously after the intravenous injection of CL and induction of SAH in group D (n=8). Enzyme-linked immunosorbent assay identifying the titer of IgG CL antibodies, neurological evaluation, cerebral angiography, and histological examination were performed in all four groups. A significant elevation of anti-CL antibodies, aggravation of neurological deficit, and reduction of caliber of the basilar artery were observed in rabbits that received the intravenous immunization of CL (group C). The administration of cyclosporin A reduced the titer of anti-CL antibody, aggravation of neurological deficit, constriction of basilar artery, and the incidence of cerebral infarction (group D). Anti-CL antibodies may therefore be involved in the deterioration of cerebral vasospasm after SAH.

Prevention of cerebral vasospasm by vasodilatory peptide maxadilan following subarachnoid hemorrhage in rabbits

Maxadilan is a vasodilatory peptide isolated from the blood-feeding sand fly Lutzomyia longipalpis. Its vasodilatory activity, estimated by the formation of erythema on rabbit skin, is greater than those of calcitonin gene-related peptide, vasoactive intestinal polypeptide and pituitary adenylyl cyclase activating polypeptide (PACAP). We have recently demonstrated that maxadilan is a specific agonist for the PACAP type I receptor, which is widely distributed in brain. Therefore, we were interested in the vasodilatory effect of maxadilan on cerebral arteries and the possibility of its clinical use for the delayed cerebral vasospasm following subarachnoid hemorrhage (SAH). In the first experiment, 10 −10 mol/kg of maxadilan (in sterile water) was injected into the cisterna magna three days after the induction of experimental SAH in rabbits ( n=6). Maxadilan dilated spastic basilar arteries within 30 min of the injection, but not at 6 h. In the second experiment, to prolong the vasodilatory effect of maxadilan, tablets containing stearic acid, hydrogenated oil, lactose, hydroxypropylcellulose and 15 mg of maxadilan were prepared. In vitro testing showed that 60% of maxadilan could be released slowly within the initial five days. In vivo experiments were performed to implant the maxadilan tablet ( n=7) and the placebo tablet ( n=6) into the cisterna magna after the induction of experimental SAH in rabbits. The spastic response of the basilar artery was maximum on day three in the placebo-treated groups. In contrast, we observed no significant change in the arterial diameter until day five in the rabbits treated with the maxadilan tablet. These data suggest that maxadilan may have therapeutic potency in treating cerebral vasospasm.

O-5 - Combination therapy with low dose nitroglycerine and fasudil hydrochloride on cerebral vasospasm in rabbit subarachnoid hemorrhage model

O-5 - Combination therapy with low dose nitroglycerine and fasudil hydrochloride on cerebral vasospasm in rabbit subarachnoid hemorrhage model