Subarachnoid Hemorrhage In Dogs Research Articles

Effect of treatment with simvastatin and cyclosporine on neurotransmitter concentrations in cerebrospinal fluid after subarachnoid hemorrhage in dogs

To measure concentrations of glutamate, aspartate, γ-aminobutyric acid (GABA), and glycine in CSF of dogs with experimentally induced subarachnoid hemorrhage (SAH) and to assess effects of cyclosporine and simvastatin on these concentrations. CSF samples from 13 dogs. In a previous study, SAH was induced in dogs via 2 injections of autologous blood into the cerebellomedullary cistern 24 hours apart. Dogs were untreated (control; n = 5) or received simvastatin alone (4) or simvastatin in combination with cyclosporine (4). Samples of CSF were collected before the first blood injection (baseline; time 0), before the second blood injection, and on days 3, 7, and 10. For the study reported here, neurotransmitter concentrations in CSF were analyzed via high-performance liquid chromatography. Data were analyzed with a repeated-measures model with adjustments for multiple comparisons by use of the Tukey method. In control dogs, the glutamate concentration peaked on day 3 and there was a significant increase in GABA and glutamate concentrations. Glutamate concentrations were significantly lower and glycine concentrations significantly higher on day 3 after administration of simvastatin alone or simvastatin in combination with cyclosporine, compared with concentrations for the control group. No significant differences in GABA and aspartate concentrations were detected among treatment groups at any time point. Glutamate concentrations were increased in the CSF of dogs with SAH. Simvastatin administration attenuated high glutamate concentrations. A combination of immunosuppression and upregulation of nitric oxide synthase may be useful in lowering high glutamate concentrations in ischemic CNS conditions.

Alteration in voltage-dependent calcium channels in dog basilar artery after subarachnoid hemorrhage

The L-type Ca++ channel antagonists like nimodipine have limited efficacy against vasospasm after subarachnoid hemorrhage (SAH). The authors tested the hypothesis that this is because SAH alters these channels, rendering them less responsible for contraction. Basilar artery smooth muscle cells were isolated 4, 7, and 21 days after SAH in dogs, and Ca++ channel currents were recorded in 10-mmol/L barium. Proteins for α₁ subunits of L-type Ca++ channels were measured by immunoblotting and isometric tension recordings done on rings of the basilar artery. High voltage-activated (HVA) Ca++ channel currents were significantly decreased and low voltage-activated (LVA) currents increased during vasospasm 4, 7, and 21 days after SAH (p < 0.05). Vasospasm was associated with a significant decrease in the number of cells with negligible LVA current while the number of cells in which the LVA current formed greater than 50% of the maximal current increased (p < 0.01). Window currents through LVA and HVA channels were significantly reduced. All changes correlated with the severity of vasospasm. There was an increase in protein for Ca(v)3.1 and Ca(v)3.3 α₁ subunits that comprise T-type Ca++ channels, a decrease in L-type (Ca(v)1.2 and Ca(v)1.3) and an increase in R-type (Ca(v)2.3) Ca++ channel α₁ subunits. Functionally, however, isometric tension studies showed vasospastic arteries still relaxed with nimodipine. Voltage-dependent Ca++ channels are altered in cerebral arteries after SAH. While decreased L-type channels may account for the lack of efficacy of nimodipine clinically, there may be other reasons such as inadequate dose, effect of nimodipine on other cellular targets, and mechanisms of vasospasm other than smooth muscle contraction mediated by activation of L-type Ca++ channels.

Effect of mild hypothermia of different duration on cerebral vasospasm following subarachnoid hemorrhage in dogs

Objective To investigate the effect of mild hypothermia of different duration on cerebral vasospasm following subarachnoid hemorrhage(SAH)in dogs.Methods Adult healthy mongrel dogs of both sexes weighing 14-20 kg were used in this study.SAH was induced by 2 injections of non-anticoagulated autologous blood0.5 ml/kg into foramen magnum at an interval of 48 h.Thirty dogs were randomly divided into 5 groups(n = 6each): group Ⅰ control(group C);group Ⅱ SAH;group Ⅲ,Ⅳ,Ⅴ SAH+8,16,32 h mild hypothermia(guoup H8 h,H16 h,H32 h).In control group artificial cerebro-spinal fluid(ACSF)0.5 ml/kg was injected into foramen magnum instead of autolegous blood.In group Ⅲ,Ⅳ,Ⅴ the dogs were cooled after the second intra-foramen magnum injection via an endovascular cooling device to 33.5℃(rectal temperature)which was maintained for 8,16 and 32 h respectively.The overall neurological performance was categorized(OPC)and scored(0 = normal.4 = coma),plasma and CSF concentrations of ET-1 and NO_2~-/NO_3~- were measured and the change in the diameter of cerebral basilar artery was determined by CT angiography before first intra-foramen magnum injection and at 5,12 and 19 d after the second injection.Results The OPC score and plasma and CSF concentrations of ET-1 were significantly increased while plasma and CSF NO_2~-/NO_3~- concentrations and diameter of cerebral basilar artery were significantly decreased after the second injection as compared with the baseline before1st injection in group SAH,H8 h and H_16 h.The OPC scores and plasma and CSF ET-1 concentrations were significantly lower while plasma and CSF NO_2~-/NO_3~- concentrations were significantly higher and the diameter of cerebral basilar artery was significantly larger in group H_16 h and H_32 h than in group SAH.Conclusion Mild hypothermia(33.5℃)maintained for 16-32 h can attenuate the cerebral vasospasm by decreasing plasma and CSF ET-1 concentration and increasing plasma and CSF NO concentration,leading to the balance between cerebral vascular constriction and dilatation. Key words: Hypothermia,induced; Subarachnoid hemorrhage; Vasospasm,intracranial

Multifaceted Effects of Selective Inhibitor of Phosphodiesterase III, Cilostazol, for Cerebral Vasospasm after Subarachnoid Hemorrhage in a Dog Model

Background: Selective inhibition of phosphodiesterase type III (PDE III) may be involved in the pathophysiology of vasospasm and a PDE III inhibitor, cilostazol, is thus expected to attenuate vasospasm after subarachnoid hemorrhage (SAH). We tested the therapeutic effects of cilostazol on angiographic and morphological vasospasm. Method: Twenty-one mongrel dogs were divided into 4 groups: (1) control (n = 3); (2) SAH (n = 6); (3) SAH with low-dose treatment (n = 6), and (4) SAH with high-dose treatment (n = 6). We used the established double-hemorrhage model of SAH achieved by injecting autologous blood. Angiography was performed on day 0 and day 7. The animals were euthanized after a second angiogram, and Western blotting was performed to analyze phenotypic changes in smooth muscle cells of the basilar artery. The basilar artery was sectioned for immunohistochemistry of SM1, SM2 and SMemb to analyze phenotypic changes (SM1, SM2 for the contractile type of smooth muscle myosin heavy chain and SMemb for the synthetic type). Intact endothelial cells were counted under a microscope. Results: Severe vasospasm was obtained in the SAH group (42 ± 1%). Cilostazol attenuated angiographic vasospasm in both treatment groups (63 ± 2 and 74 ± 4%, respectively). Prevention of endothelial damage and phenotypic changes in smooth muscle cells were observed in both treatment groups (p < 0.05 vs. control, ANOVA). Conclusion: Cilostazol attenuates vasospasm following SAH in dogs by suppressing phenotypic changes in the basilar artery and preventing endothelial damage. Therefore, we anticipate that cilostazol may be useful in the management of vasospasm.

Effects of graded hyperventilation on cerebral oxygen metabolism in a cisterna magna blood injection model of subaraclmoid hemorrhage in dogs

Objective To investigate effects of graded hyperventilation on cerebral oxygen metabolism in a cisterna magna blood injection model of subarachnoid hemorrhage in dogs. Methods A model of subarachnoid hemorrhage in dogs was established by using two injections of autologous blood into cisterna magna. Twenty-four male dogs weighing 12-18 kg were randomly divided into four groups (n=6 each): group N normally ventilated (PETCO2 35-40 mm Hg), group L lightly ventilated (PETCO2 30-35 mm Hg), group M moderately ventilated (PETCO2 25-30 mm Hg) and group P profoundly ventilated (PETCO2 20-25 mm Hg). The expected PETCO2 levels were maintained through adjustment of respirator parameters. The dogs were ventilated for 4 h and the anesthetics were discontinued. Vital signs, intracerebral pressure (ICP), jugular venous oxygen saturation (SjvO2), jugular venous oxygen pressure (PjvO2), arterio-jugular venous oxygen content difference (Da-jvO2), cerebral oxygen extraction ratio (ERO2) and arterio-jugular venous differences of lactate (Djv-aL) were recorded at 30 min after two injections of blood (T0) and at 1, 2, 3, 4 h(T1-4) following mechanically ventilated. Blood samples were drawn from cephalic vein of forelimb to determine S-100B protein before the first injection of blood, at T0-4 and at 4, 12,20,44,92 and 188 h (T5-10)after ventilation. Results Compared with group N, ICP at T1-4 was significantly decreased in the other groups, Da-jvO2 and ERO2 significantly increased in group M and H, Djv-aL significantly increased in group H and at T2-4 in group M, SjvO2 significantly decreased at T2,3 in group H and S-100B protein concentration significantly elevated at T1-10 in group H (P<0.05). Compared with T0, S-100B protein concentration significantly elevated at T5-8 in group N, M and H and at T4-8 in group L (P<0.05). Conclusion Mild hyperventilation and moderate hyperventilation does not aggravate bruin injury, while profound hyperventilation exacerbates brain injury due to imbalance between cerebral oxygen supply and consumption after subarachnoid hemorrhage in dogs. Key words: Hyperventilation; Subarachnoid hemorrhage; Brain; Oxygen comsumption

Temporal profile of potassium channel dysfunction in cerebrovascular smooth muscle after experimental subarachnoid haemorrhage

The pathogenesis of cerebral vasospasm after subarachnoid haemorrhage (SAH) involves sustained contraction of arterial smooth muscle cells that is maximal 6-8 days after SAH. We reported that function of voltage-gated K+ (KV) channels was significantly decreased during vasospasm 7 days after SAH in dogs. Since arterial constriction is regulated by membrane potential that in turn is determined predominately by K+ conductance, the compromised K+ channel dysfunction may cause vasospasm. Additional support for this hypothesis would be demonstration that K+ channel dysfunction is temporally coincident with vasospasm. To test this hypothesis, SAH was created using the double haemorrhage model in dogs and smooth muscle cells from the basilar artery, which develops vasospasm, were isolated 4 days (early vasospasm), 7 days (during vasospasm) and 21 days (after vasospasm) after SAH and studied using patch-clamp electrophysiology. We investigated the two main K+ channels (KV and large-conductance voltage/Ca2+-activated (KCa) channels). Electrophysiologic function of KCa channels was preserved at all times after SAH. In contrast, function of KV channels was significantly decreased at all times after SAH. The decrease in cell size and degree of KV channel dysfunction was maximal 7 days after SAH. The results suggest that KV channel dysfunction either only partially contributes to vasospasm after SAH or that compensatory mechanisms develop that lead to resolution of vasospasm before KV channels recover their function.

Induction of housekeeping gene expression after subarachnoid hemorrhage in dogs

Changes in gene expression are commonly assessed relative to the expression of housekeeping genes, which are assumed to remain unchanged. We tested this assumption in cerebral arteries obtained from dogs 4 and 7 days after subarachnoid hemorrhage (SAH) had been created using the double hemorrhage model. Basilar arteries were removed and examined for expression of messenger ribonucleic acid (mRNA) levels using quantitative real-time polymerase chain reaction. Cross-sections of basilar arteries were stained immunohistochemically for proliferating cell nuclear antigen (PCNA) and 4′,6-diamidino-2-phenylindole (DAPI). Positively stained cells were counted and numbers obtained were normalized to the cross-sectional area. The results were compared to normal dog basilar arteries contracted pharmacologically in vitro. SAH resulted in significant vasospasm ( P < 0.001 for each, paired t-tests). There were significant increases in mRNA for β-actin (441%, P = 0.01), glyceraldehyde-3-phosphate dehydrogenase (566%, P = 0.007) and 18S ribosomal RNA (320%, P = 0.025) 7 days after SAH. Total mRNA was increased 7 days after SAH relative to genomic DNA (157%, P = 0.009). There were significant increases in the number of cells in the tunica media and adventitia of arteries after SAH and a significant decrease in the media after contraction in vitro. Cells in the tunica media and adventitia labeled with PCNA were significantly increased at both times after SAH. Transcripts for housekeeping genes are increased after SAH, making standardization to them potentially invalid. The increase is due to proliferation of cells in the adventitia and increased total mRNA in the media and adventitia.

Preserved BK Channel Function in Vasospastic Myocytes from a Dog Model of Subarachnoid Hemorrhage

Cerebral vasospasm after subarachnoid hemorrhage (SAH) is due to contraction of smooth muscle cells in the cerebral arteries. The mechanism of this contraction, however, is not well understood. Smooth muscle contraction is regulated in part by membrane potential, which is determined by K⁺ conductance in smooth muscle. Voltage-gated (Kv) and large-conductance, Ca²⁺-activated K⁺ (BK) channels dominate arterial smooth muscle K⁺ conductance. Vasospastic smooth muscle cells are depolarized relative to normal cells, but whether this is due to altered Kv or BK channel function has not been determined. This study determined if BK channels are altered during vasospasm after SAH in dogs. We first characterized BK channels in basilar-artery smooth muscle using whole-cell patch clamping and single-channel recordings. Next, we compared BK channel function between normal and vasospastic cells. There were no significant differences between normal and vasospastic cells in BK current density, kinetics, Ca²⁺ and voltage sensitivity, single-channel conductance or apparent Ca²⁺ affinity. Basilar-artery myocytes had no, small- or intermediate-conductance, Ca²⁺-activated K⁺ channels. The lack of difference in BK channels between vasospastic and control cells suggests alteration(s) in other K⁺ channels or other ionic conductances may underlie the membrane depolarization and vasoconstriction observed during vasospasm after SAH.

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 alpha-toxin. Endothelium was removed from all arteries. Vasospastic arteries demonstrated significantly reduced contractility to KCl with a shift in the EC(50) toward 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.

Reversal of cerebral vasospasm by sphenopalatine ganglion stimulation in a dog model of subarachnoid hemorrhage

Background Sphenopalatine ganglion stimulation dilates the ipsilateral arteries of the normal dog anterior circle of Willis. This experiment tested whether similar stimulation would reverse cerebral vasospasm. Methods Six dogs underwent baseline angiography followed by creation of subarachnoid hemorrhage (SAH) by injection of autologous blood into the cisterna magna. Two days later, subarachnoid blood injection was repeated. Seven days later, angiography was repeated and the left sphenopalatine ganglion was exposed microsurgically. Angiography was repeated 15 minutes after exposure of the ganglion. The ganglion was then stimulated electrically 3 times and angiography repeated during, and 15 and 30 minutes after stimulation. The protocol was repeated again. Adequacy of stimulation was confirmed by the presence of immediate ipsilateral nasal mucus production. Results Subarachnoid hemorrhage was associated with significant vasospasm of both middle cerebral arteries (11% ± 4% and 18% ± 7%, P < .05, paired t tests). Exposure of the ganglion and sham stimulation produced no substantial changes in arterial diameters compared with the diameter before stimulation and after ganglion exposure (n = 2-6 per measurement, paired t tests). Ganglion stimulation produced significant dilatation of the ipsilateral extracranial and intracranial internal carotid, middle cerebral, and anterior cerebral arteries compared with the contralateral arteries (13% ± 6% to 32% ± 14%, P < .05, paired t tests). Conclusions The mild to moderate vasospasm that results from SAH in dogs was reversed by sphenopalatine ganglion stimulation. Since this method carries a potential for human application, additional studies are warranted to determine the effects on more severe vasospasm.

Time course of production of hydroxyl free radical after subarachnoid hemorrhage in dogs

Vasospasm after subarachnoid hemorrhage (SAH) is associated with lipid peroxidation. However, lipid peroxides increase in a delayed fashion after SAH and may be a byproduct of but not a cause of vasospasm. This study correlated vasospasm with hydroxyl free radical and lipid peroxide levels. 24 dogs had baseline cerebral angiography and induction of SAH by 2 injections of blood into the cisterna magna at baseline and 2 days later. Angiography was repeated 4, 7, 10, 14 or 21 days after the first injection (n = 4 per group) and a microdialysis catheter was inserted into the premedullary cistern. Control dogs (n = 4) underwent angiography and microdialysis but not SAH. Salicylic acid, 100 mg/kg, was administered intravenously, and microdialysis fluid was collected and analyzed by high pressure liquid chromatography for 2,3- and 2,5-dihydroxybenzoic acids (DHBA). Malondialdehyde was measured in subarachnoid clot removed from the prepontine cistern and in the basilar artery itself at the time of euthanasia. Significant vasospasm developed 4 to 14 days after SAH. Malondialdehyde levels were significantly elevated in the basilar artery and subarachnoid clot 4 days after SAH (p < 0.0001, ANOVA) but not at other times. 2,5-DHBA levels were significantly greater than control at 4 to 14 days and they peaked at 4 days (p < 0.05, ANOVA). 2,3-DHBA was significantly increased at 4 days after SAH (p < 0.05, ANOVA). There were significant correlations between basilar artery malondialdehyde levels and vasospasm and cerebrospinal fluid 2,5-DHBA levels and vasospasm. These results suggest the presence of hydroxyl free radical after SAH and demonstrate a correlation between such production, as measured by trapping with salicylate, and the early phase of vasospasm. The correlation with vasospasm implicates free radicals and lipid peroxidation in this phase of vasospasm.

Evaluation of the microvasculature and cerebral ischemia after experimental subarachnoid hemorrhage in dogs.

Whether cerebral vasospasm occurs only in surface vessels or also in parenchymal arterioles is debatable. The present study was undertaken to evaluate comprehensively the microvasculature of the brainstem after experimental subarachnoid hemorrhage (SAH). Nine mongrel dogs of either sex, each weighing between 18 and 24 kg, underwent double blood injections spaced 48 hours apart; the injections were infused into the cisterna magna immediately after angiography of the basilar arteries (BAs). Three additional dogs assigned to a control group received no blood injections. The dogs were killed on Day 7. Axial sections obtained from the midpontine region of both control dogs and animals subjected to SAH were evaluated with respect to the morphological characteristics of vessels and neurons, and for ultrastructural changes. Severe vasospasm occurred in the BAs of all dogs subjected to SAH. Nevertheless, in these animals, the luminal areas and vessel perimeter in parenchymal arterioles, but not in parenchymal venules, were observed to have increased when compared with those of control dogs (p < 0.01, t-test). No corrugation of the internal elastic lamina was observed and smooth-muscle and endothelial cells remained normal at the ultrastructural level in the dogs with SAH. In this model, vasospasm of the BAs did not extend into the region of the pons to affect the intraparenchymal arterioles. Dilation of the parenchymal arterioles might serve as compensation for reduced blood flow. Thus, no neuronal ischemia or infarction resulted in the pontine region of the brain.

Histological dissociation between intra- and extraparenchymal portion of perforating small arteries after experimental subarachnoid hemorrhage in dogs.

This study was conducted to investigate whether the intraparenchymal and extraparenchymal portions of small cerebral arteries show different histopathological changes after subarachnoid hemorrhage (SAH). SAH was produced in dogs by a two-hemorrhage method, and the dogs were perfusion-fixed at 7 and 14 days after SAH. Normal untreated animals were also examined to determine whether or not the histological and morphological changes in the perforating arteries were affected by the perfusion pressure during perfusion-fixation. Control dogs, which received cisternal injection of saline, and untreated normal dogs, which were divided into two groups depending on the perfusion pressure during perfusion-fixation, were also examined. Microvascular corrosion casts produced by arterial injection of polyester resin were examined by scanning electron microscopy (SEM) with morphometric analysis of the caliber of the small perforating arteries. Slices sectioned parallel to the pontine surface were examined by SEM and by light microscopy with morphometric analysis of the luminal diameter and wall thickness of the small perforating arteries. Corrosion casts showed irregular width with folds in the perforating arteries 7 days after SAH. Sectioned slices showed an increased wall thickness of the perforating arteries with intimal corrugation 7 days after SAH. Morphometric analysis revealed that the extraparenchymal portion of the perforating arteries showed no significant differences between any of the groups tested; however, the intraparenchymal portion showed a significant decrease of luminal diameter 7 days after SAH, and a significant increase of wall thickness 7 and 14 days after SAH. The perfusion pressure during perfusion-fixation did not affect the histological changes in the perforating arteries. The results of this study showed that the vasoconstrictive response of the perforating arteries to SAH was different between the extraparenchymal and the intraparenchymal portion, and showed that the intraparenchymal portion of the perforating arteries constrict after SAH, which may affect cerebral ischemia during cerebral vasospasm by increasing total cerebrovascular resistance.

Platelet-derived growth factor (PDGF-AB) like immune reactivity in serum and in cerebral spinal fluid following experimental subarachnoid haemorrhage in dogs.

The aim of this study was to evaluate the following questions: Can the platelet-derived growth factor (PDGF-AB) be identified in the serum and cerebro spinal fluid (CSF) of dogs? Is there an increase in the concentration of PDGF-AB following experimental subarachnoid haemorrhage (SAH)? Is the increase in concentration related to the angiographic cerebral vasospasm of the basilar artery. The "double haemorrhage" model was applied in seven dogs to produce experimental SAH with determination of angiographic vasospasm in the basilar artery. Blood and CSF samples were taken on the first, third and eighth days. The analyses were performed with an ELISA human PDGF-AB antibody kit (quantikine human PDGF-AB, R&D Systems, Minneapolis, USA). The average PDGF-AB base value in the serum on the day before the SAH was 410.77 +/- 177.56 pg/ml, in the CSF it was 6.43 +/- 3.19 pg/ml. There was a significant (p = 0.05) increase in the concentration of PDGF-AB (third day 717.35 pg/ml, eighth day 918.07 pg/ml) in the serum of all animals. No significant increase was found in the CSF samples of any animal. In summary, a PDGF-AB like immune reactivity was found in the serum of dogs with the human PDGF-AB ELISA kit and the concentration of PDGF-AB in the serum increased after experimental SAH but not in CSF, but there was no relationship between the increase in PDGF-AB serum concentration and angiographic vasospasm.

U74389G Prevents Vasospasm after Subarachnoid Hemorrhage in Dogs

U74389G Prevents Vasospasm after Subarachnoid Hemorrhage in Dogs

U74389G prevents vasospasm after subarachnoid hemorrhage in dogs.

Oxygen-derived free radicals may contribute to vasospasm after the rupture of an intracranial aneurysm through direct vasoconstricting effects occurring within the arterial wall or, secondarily, by causing lipid peroxidation in the subarachnoid erythrocytes with secondary induction of vasoconstriction. U74389G is a potent inhibitor of lipid peroxidation and a scavenger of oxygen-derived free radicals. This study determined the relative contributions of oxygen-derived free radicals and lipid peroxidation to vasospasm in the double-hemorrhage dog model. Sixteen dogs underwent baseline (Day 0) cerebral angiography and induction of subarachnoid hemorrhage by two injections of blood into the cisterna magna 2 days apart. They were randomized to receive drug vehicle (n=8) or U74389G (n=8, 3 mg/kg of body weight/d) intravenously. Drug administration and end point analysis were blinded. The end points were angiographic vasospasm, as assessed by comparison of angiograms obtained before and 7 days after subarachnoid hemorrhage, and the levels of malondialdehyde and salicylate hydroxylation products (dihydroxybenzoic acids) in cerebrospinal fluid and of malondialdehyde in subarachnoid blood clots and basilar arteries 7 days after hemorrhage. Comparisons within groups of Day 0 and Day 7 angiograms and between groups of angiograms obtained at Day 7, showed significant vasospasm in animals in the vehicle group (mean+/-standard error, 51%+/-4) but not in the U74389G group (25%+/-11, P < 0.05, unpaired t test). High-pressure liquid chromatographic assays of malondialdehyde and dihydroxybenzoic acids in cerebrospinal fluid, subarachnoid blood clots, and basilar arteries showed no significant differences between groups. The significant prevention of vasospasm by U74389G without change in levels of indicators of free radical reactions suggests that the effect of the drug is related to other processes occurring in the arterial wall and that cerebrospinal fluid levels of oxygen radicals and lipid peroxides are not useful markers of vasospasm.

U74389G Prevents Vasospasm after Subarachnoid Hemorrhage in Dogs

U74389G Prevents Vasospasm after Subarachnoid Hemorrhage in Dogs

U74389G Prevents Vasospasm after Subarachnoid Hemorrhage in Dogs

U74389G Prevents Vasospasm after Subarachnoid Hemorrhage in Dogs

U74389G Prevents Vasospasm after Subarachnoid Hemorrhage in Dogs

U74389G Prevents Vasospasm after Subarachnoid Hemorrhage in Dogs

Prevention of vasospasm after subarachnoid hemorrhage in dogs by continuous intravenous infusion of PD156707.

This randomized, blinded study tested the prophylactic effect of PD156707, a nonpeptide competitive antagonist of endothelin A receptors, against vasospasm after subarachnoid hemorrhage in dogs. Twenty-two dogs were allocated on day 0 to undergo cerebral angiography followed by injection of arterial blood (0.5 ml/kg) into the cisterna magna. Dogs had central venous catheters implanted for continuous infusion of drug vehicle (n = 10) or PD156707 (n = 12). Cisternal blood injection was repeated on day 2. Drug levels were measured in plasma on days 2, 4, 6, and 7 and in cerebrospinal fluid (CSF) on days 2 and 7. Angiography was repeated on day 7 to assess vasospasm. After angiography on day 7, acute effects of infusion of PD156707, 100 mg, or drug vehicle on established vasospasm were assessed. Analysis of physiological variables within (analysis of variance) groups across time and between (unpaired t-test) groups at each time showed that drug-treated animals had significantly increased heart rate on day 7 compared to day 0 (p < 0.005). Comparison of basilar artery diameters at day 7 showed that PD156707 significantly decreased the degree of basilar artery vasospasm (placebo: -47 +/- 5% reduction [mean +/- SE] versus PD156707: -28 +/- 7%, p < 0.05, unpaired t-test). There was, however, significant vasospasm when comparing within groups (paired t-test, placebo: p < 0.0001, PD156707: p < 0.005). Mean plasma PD156707 levels (322 +/- 123 ng/ml) were adequate to block responses of endothelin-1 on endothelin A receptors in vitro although CSF levels (11 +/- 7 ng/ml) were substantially lower. Infusion of PD156707 into the basilar artery on day 7 caused a small but significant 10 +/- 3% (paired t-test, p < 0.01) increase in diameter compared to placebo (3 +/- 3% increase, p = 0.32). This infusion also was associated with a substantial increase in CSF drug levels to 19 +/- 9 mg/ml. These results suggest that endothelin A receptors mediate some of the vasospasm that occurs after SAH in dogs and that blockade of these receptors may be a beneficial treatment for vasospasm.