Subarachnoid hemorrhage in the rat: cerebral blood flow and glucose metabolism after selective lesions of the catecholamine systems in the brainstem

LPS Pretreatment Provides Neuroprotective Roles in Rats with Subarachnoid Hemorrhage by Downregulating MMP9 and Caspase3 Associated with TLR4 Signaling Activation

Subarachnoid hemorrhage (SAH), as a severe brain disease, has high morbidity and mortality. SAH usually induced neurological dysfunction or death and the treatment is far from satisfaction. Here, we investigated the effect of low dose of LPS pretreatment and underlying molecular mechanism in rat SAH model. Firstly, SAH model was induced by prechiasmal cistern injection method (SAH1) and common carotid artery-prechiasmal cistern shunt method (SAH2), respectively, to select the more suitable SAH model. At 6, 12, 24, 48, and 72 h after SAH, brain injury including neurological dysfunction, blood-brain barrier disruption, brain edema, and cell apoptosis were detected. And the expression of MMP9, HMGB1/TLR4, and caspase3 in cortex were also explored. Then, SB-3CT, an inhibitor of MMP9, was administrated to investigate the exact function of MMP9 in the brain injury at 24 h after SAH. Moreover, low dose of LPS was used to verify whether it had nerve protection after SAH and the mechanism involving in MMP9 and caspase 3 was investigated. Our results showed SAH1 seems to be the most suitable SAH model. In addition, MMP9 activated by HMGB1/TLR4 may promote or aggravate brain injury, while inhibiting MMP9 via SB-3CT exerted a neuroprotective effect. Moreover, LPS improved the neurological dysfunction, reduced Evans blue extravasation and brain edema, and inhibited cell apoptosis of cortex in rats with brain injury induced by SAH. Importantly, LPS pretreatment increased the expression level of TLR4, and decreased the level of MMP9 and caspase3. Therefore, the present study revealed that low dose of LPS pretreatment could provide neuroprotective effects on brain injury caused by SAH via downregulating MMP9 and caspase3 and activating TLR4 signal pathway.

Mechanisms of acute brain injury after subarachnoid hemorrhage

Brain injury after subarachnoid hemorrhage (SAH) is a biphasic event with an acute ischemic insult at the time of the initial bleed and secondary events such as cerebral vasospasm 3 to 7 days later. Although much has been learned about the delayed effects of SAH, less is known about the mechanisms of acute SAH-induced injury. Distribution of blood in the subarachnoid space, elevation of intracranial pressure, reduced cerebral perfusion and cerebral blood flow (CBF) initiates the acute injury cascade. Together they lead to direct microvascular injury, plugging of vessels and release of vasoactive substances by platelet aggregates, alterations in the nitric oxide (NO)/nitric oxide synthase (NOS) pathways and lipid peroxidation. This review will summarize some of these mechanisms that contribute to acute cerebral injury after SAH.

A new percutaneous model of Subarachnoid Haemorrhage in rats

OBJECTIVE

Describe the results obtained with a new percutaneous, intracisternal model of Subarachnoid Haemorrhage (SAH) in Wistar rats by a single injection of non-heparinised, autologous blood.

METHODS

Once anaesthetized the rat was fixed prone in a stereotaxic frame. After identifying the projection of the occipital bone, the needle of the stereotaxic frame aspirated towards the foramen magnum until it punctured through the atlanto-occipital membrane and obtained cerebrospinal fluid. Autologous blood (100 μl) was withdrawn from the tail and injected intracisternally. This procedure was repeated in the sham group, injecting 100 μl of isotonic saline. On the fifth day post-intervention, the rats were anaesthetized and the brain was exposed. After a lethal injection of ketamine the brain was explanted and fixed in paraformaldehyde. Gross and microscopic inspection of the slices revealed the existence or non-existence of pathological findings.

RESULTS

A total of 26 rats were operated on (13 in the SAH group/13 in the sham group). The average time between obtaining the blood and the start of the intracisternal injection was 10 (±1.2)s. The mortality rate was 16.12%. Intra- and extraparenchymal ischemic-haemorrhagic lesions were found in three animals (23.07%)--all from the SAH group--with ischemic neuronal cell injury detected in two of the three.

CONCLUSIONS

The new murine model of SAH is easy to perform, with low mortality, minimally invasive, which makes it interesting for future studies on vasospasm-related delayed SAH complications.

Severe Symptomatic Vasospasm following Intraventricular Hemorrhage from Arteriovenous Fistula

The authors present a rare case of severe vasospasm following the rupture of arteriovenous fistula. On initial CT scan, hematoma in the corpus callosum and left inferior frontal region with surrounding cerebromalacia and all ventricles without apparent subarachnoid hemorrhage were seen. Angiograms showed arterivenous fistula but did not show cerebral vasospasm. Thirteen days after admission the neurological state of patient suddenly deteriorated and bilateral motor weaknesses developed. Following angiograms revealed severe narrowing on the supraclinoid portion of bilateral internal carotid arteries, bilateral anterior cerebral arteries and bilateral middle cerebral arteries. Transluminal angioplasty and intra-arterial papaverine infusion were performed. The patient remained stable with moderate neurologic deficits.

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.

Experimental subarachnoid haemorrhage models in rats

There is no comprehensive and reliable model available in small animals that are suitable for the study of subarachnoid haemorrhage (SAH). In the study we reviewed the advantages and disadvantages of available SAH models in rats and presented our model. Experimental SAH was induced in a group of 350-450 g Sprague-Dawley rats. A 2 mm-diameter burr hole was drilled and, working under a microscope, haemorrhage was produced by transclival puncture of the basilar artery with a 20 microns thick piece of glass. The rats were assigned to either the experimental group (n: 7) or the control group (n: 7). Local cerebral blood flow (LCBF), intracranial pressure (ICP), and cerebral perfusion pressure (CPP) were measured for 60 min after SAH, after which the rats were decapitated. Microscopic examinations were done on three different segments of the basilar artery. There was a significant and sharp drop in LCBF just after SAH was induced (56.17 +/- 12.80 mlLD/min/100 g and 13.57 +/- 5.85 mlLD/min/100 g for baseline and post-SAH, respectively; p < 0.001), the flow slowly increased by the end of the experiment but never recovered to pre-SAH values (43.63 +/- 7.6 mlLD/min/100 g, p < 0.05). ICP (baseline 7.33 +/- 0.8 mmHg) increased acutely to 70.6 +/- 9.2 mmHg, and also returned to normal levels by 60 min after SAH. CPP (baseline 75.1 +/- 4.9 mmHg) dropped accordingly (to 21.0 +/- 6.3 mmHg) and then increased, reaching 70.1 +/- 4.9 mmHg at 60 min after SAH. Examinations of the arteries revealed decreased inner luminal diameter and distortion of the elastica layer. We present an inexpensive and reliable model of SAH in the rat that allows single and multiple haemorrhages and to study the early and late course of pathological changes.

Experimental subarachnoid hemorrhage: subarachnoid blood volume, mortality rate, neuronal death, cerebral blood flow, and perfusion pressure in three different rat models

OBJECTIVE

To investigate which of three subarachnoid hemorrhage (SAH) models is the most suitable for studies of pathological and pathophysiological processes after SAH.

METHODS

SAH was induced in rats via intracranial endovascular perforation (perforation model), blood injection into the cisterna magna (300 microl), or blood injection into the prechiasmatic cistern (200 microl). The subarachnoid blood volume was quantitatively measured. Cerebral blood flow (CBF) (as assessed with laser Doppler flowmetry), intracranial pressure, and mean arterial blood pressure were recorded for 90 minutes after SAH. Mortality was recorded, and neuronal death was assessed in animals that survived 7 days after SAH.

RESULTS

The subarachnoid blood volume was close to the injected amount after prechiasmatic SAH. In the other models, the volume varied between 40 and 480 microl. The mortality rates were 44% in the perforation SAH group, 25% in the prechiasmatic SAH group, and 0% in the cisterna magna SAH group; the corresponding values for neuronal death were 11, 44, and 28%. Cerebral perfusion pressure approached baseline values within 5 minutes after SAH in all three models. CBF decreased to approximately 35% of baseline values immediately after SAH in all groups; it gradually increased to normal values 15 minutes after SAH in the cisterna magna SAH group and to 60 and 89% of baseline values 90 minutes post-SAH in the perforation and prechiasmatic SAH groups. CBF was significantly correlated with the subarachnoid blood volume.

CONCLUSION

The prechiasmatic SAH model seems to be the most suitable for study of the sequelae after SAH; it produces a significant decrease in CBF, an acceptable mortality rate, and substantial pathological lesions, with high reproducibility. The CBF reduction is predominantly dependent on the amount of subarachnoid blood.

Subarachnoid hemorrhage induces dynamic changes in regional cerebral metabolism in rats

Following a subarachnoid hemorrhage (SAH), adult rats exhibit dynamic regional changes in cerebral glucose metabolism characterized by an increase in metabolic rates and a subsequent upregulation of cytochrome oxidase (CO). We evaluated both local cerebral metabolic rates for glucose (ICMRglc: (mol/100 g/min) and CO in 23 brain regions of interest (ROI). Sham animals underwent anesthesia and superficial surgery; saline-controls received an injection of 0.9% saline into the cisterna magna; and SAH rats received an injection of autologous blood into the cisterna magna. This blood, measured by albumin labeled with radioactive carbon 14, distributed throughout the brain but predominated ventrally. After experimental animals were sacrificed at day 0 (3 h), 1, 3, and 7 days postinjection, ROI were analyzed using [14C]2-deoxy-D-glucose autoradiography and CO histochemistry. ICMRglc in SAH rats increased in many regions (ranging from 0.7% to 32.2% above sham levels). Cytochrome oxidase also increased from 1% to 9% above sham levels, peaking on day 3. Conversely, saline-controls exhibited prolonged depression of ICMRglc (ranging from 11% to 35% below sham levels) and CO (ranging from 4% to 11% below sham levels) from day 0 through day 7. All saline-control ROI for all time points showed this metabolic depression, and between 91% and 95% of saline-control ROI presented lower CO levels as compared to sham. Overall, ICMRglc and CO levels were greater in SAH than in saline-control ROI. However, when considering the influence of subarachnoid blood on metabolic changes in SAH animals, both CO and 2DG levels did not correlate well with the amount of 14C-albumin binding. While previous studies have measured both metabolic rates of glucose and CO soon after SAH, this is the first to simultaneously conduct these measurements in the same SAH rat model.

Effect of moderate hypothermia on experimental severe subarachnoid hemorrhage, as evaluated by apparent diffusion coefficient changes

OBJECTIVE

The aims of this study were to investigate the early changes in the mean apparent diffusion coefficient (ADC) after severe subarachnoid hemorrhage (SAH), as a marker of ischemic damage, and to examine the effects of moderate hypothermia, induced at various time points, on ADC changes.

METHODS

ADC maps were calculated from diffusion-weighted, blipped-epi, spin echo, magnetic resonance imaging sequences (2.35-T BIOSPEC 24/40 scanner; Bruker Medizin Technik GmbH, Karlsruhe, Germany) for 21 anesthetized (0.45-1% halothane, temperature-adjusted/30% oxygen/69% nitrogen) and ventilated Wistar rats. After baseline scanning, bolus injection of 0.5 ml of autologous arterial blood or artificial cerebrospinal fluid (control group), into the cisterna magna, was performed. Serial scanning was performed for 3 hours after injection, using normothermic or hypothermic (32 degrees C) rats. In an additional series of experiments, hypothermia was initiated either immediately or 60 minutes after normothermic SAH. The water contents of the removed brains were calculated using the wet/dry weight method.

RESULTS

The ADC values did not change in the control group but decreased to 88.6+/-5.2% (P < 0.05 versus baseline) after SAH and remained significantly decreased throughout the experiment in normothermia. An injection of blood during hypothermia caused an initial decrease in ADC to 96.1+/-5.6% (P < 0.05 versus baseline); values continuously increased and reached normal levels within 60 minutes. Delayed hypothermia also normalized ADC values within the observation period. The brain water content in the control group was 80.3+/-0.1%, that after SAH in normothermia was 81.1+/-0.7%, and that after SAH in hypothermia was 79.3+/-0.5%.

CONCLUSION

This model of severe SAH in rats causes significant ADC changes, which are reversible by application of moderate hypothermia even when it is induced after a 60-minute delay. These findings support the concept of moderate hypothermia exerting a neuroprotective effect in severe SAH.

Acute and delayed vasoconstriction after subarachnoid hemorrhage: local cerebral blood flow, histopathology, and morphology in the rat basilar artery

The decreased local cerebral blood flow (LCBF) and cerebral ischemia that occur after subarachnoid hemorrhage (SAH) may be caused by acute and/or delayed vasospasm. In 36 Sprague-Dawley (350-450 g) rats SAH was induced by transclival puncture of the basilar artery. Mean arterial blood pressure (MABP), LCBF, intracranial pressure (ICP), and cerebral perfusion pressure (CPP) were measured in all rats for 30 min before and 60 min after SAH was induced. One set of control (n : 7) and experimental animals (n : 7) was sacrificed after the 60 min of initial post-hemorrhage measurements were recorded. Four days after SAH induction, LCBF and MABP were measured again for 60 min in subgroups of surviving experimental rats (n : 7) and control rats (n : 7). Histopathologic and morphologic examinations of the basilar artery were performed in each subgroup. There was a sharp drop in LCBF just after SAH was induced (55.50 +/- 11.46 mlLD/min/100 g and 16.1 +/- 3.6 mlLD/min/100 g for baseline and post-SAH, respectively; p < 0.001). The flow then gradually increased but had not returned to pre-SAH values by 60 min (p < 0.05). At 4 days after SAH induction, although LCBF was lower than that observed in the control group and pre-SAH values, it was not significantly different from either of these flow rates (p > 0.05). ICP (baseline 7.05 +/- 0.4 mmHg) increased acutely to 75.2 +/- 7.1 mmHg, but returned to normal levels by 60 min after SAH. CPP (baseline 84.5 +/- 6.3 mmHg) dropped accordingly (to 18.6 +/- 3.1 mmHg), and then increased, reaching 72.2 +/- 4.9 mmHg at 60 min after SAH (p > 0.05). Examinations of the arteries revealed decreased inner luminal diameter and distortion of the elastica layer in the early stage. LCBF in nonsurviver rats (n : 8) was lower than that in the animals that survived (p < 0.01). At 4 days post-hemorrhage, the rats' basilar arteries showed marked vasculopathy. The findings showed that acute SAH alters LCBF, ICP, and CPP, and that decreased LCBF affects mortality rate. Subsequent vasculopathy occurs in delayed fashion, and this was observed at 4 days after the hemorrhage event.

Multiple interstitial substances measured by microdialysis in patients with subarachnoid hemorrhage

OBJECTIVE

Intracerebral microdialysis is a tool to monitor metabolic disturbances in the brains of patients with severe head injuries or subarachnoid hemorrhage (SAH). In the search for putative indicators of primary and secondary brain damage, we measured multiple metabolites in the dialysates of patients with SAH, to elucidate their significance for the outcomes of the patients as well as their temporal profiles of liberation after the insult.

METHODS

Microdialysis probes were placed, with a ventriculostomy catheter for drainage of cerebrospinal fluid, into a frontal lobe of 10 patients with aneurysmal SAH, for 4.6 +/- 0.5 days. Amino acids, metabolites of glycolysis, purines, catecholamines, and nitric oxide oxidation byproducts were measured by high-performance liquid chromatography. Spearman's correlation coefficient and Student's t test were used to compare the levels of the metabolites with the outcomes of the patients, as assessed using the Glasgow Outcome Scale, 3 months after the ictus.

RESULTS

For patients with unfavorable outcomes (Glasgow Outcome Scale scores of 1-3), which were primarily associated with the development of large infarctions, dialysate levels of excitatory amino acids increased up to 30-fold, those of lactate up to 10-fold, and those of nitrite up to 5-fold, compared with normal levels observed for patients with favorable outcomes (Glasgow Outcome Scale scores of 4 or 5). When average peak concentrations in the dialysates of patients with favorable and unfavorable outcomes were compared, significantly higher levels of excitatory amino acids, taurine, lactate, and nitrite, but not of purines and catecholamines, were observed for those with poor outcomes (P < 0.05). With respect to the temporal profiles of the average metabolite concentrations, the significantly increased levels of amino acids observed for patients with poor outcomes followed a biphasic course, with maximal concentrations on the first and second days or the seventh day after the insult (P < 0.01).

CONCLUSION

These data confirm the usefulness of excitatory amino acids and lactate as major parameters for neurochemical monitoring for patients threatened by acute cerebral disorders. Other substances, such as taurine and nitrite, were also demonstrated to be potentially predictive. Release of these substances into the extracellular fluid of the brain might be particularly relevant for the development of secondary brain damage after SAH, e.g., infarction or brain swelling.

Effects of S-nitrosoglutathione on acute vasoconstriction and glutamate release after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage (SAH) causes acute vasoconstriction that contributes to ischemic brain injury shortly after the initial bleed. It has been theorized that decreased availability of nitric oxide (NO) may contribute to acute vasoconstriction. Therefore we examined the effect of the NO donor N-nitroso glutathione (GSNO) on acute vasoconstriction and early ischemic glutamate release after experimental SAH.

METHODS

SAH was induced by the endovascular suture method in anesthetized rats. GSNO (1 micromol/L/kg, n=31) or saline (n=21) was injected 5 minutes after SAH. Sham-operated rats received GSNO (1 micromol/L/kg, n=5) 5 minutes after sham surgery. Arterial and intracranial pressures, cerebral blood flow (CBF), and extracellular glutamate release were measured serially for 60 minutes after SAH. SAH size was determined, and vascular measurements were made histologically.

RESULTS

GSNO had no effect on resting blood pressure, intracranial pressure, cerebral perfusion pressure, or CBF in sham-operated animals. However, administration of GSNO after SAH was associated with significantly increased CBF (161.6+/-26.6% versus saline 37.1+/-5.5%, 60 minutes after SAH, P<0.05), increased blood vessel diameter (internal carotid artery [ICA] 285.0+/-16.5 microm versus saline 149.2+/-14.1 microm, P<0.01), decreased vessel wall thickness (ICA12.9+/-0.7 microm versus saline 25.1+/-1.6 microm, P<0.01), and decreased extracellular glutamate levels (3315.6+/-1048.3% versus saline469. 7+/-134.3%, P<0.05). Blood pressure decreased transiently, whereas intracranial pressure, cerebral perfusion pressure, and SAH size were not affected.

CONCLUSIONS

These results suggest that GSNO can reverse acute vasoconstriction and prevent ischemic brain injury after SAH. This further implies that acute vasoconstriction contributes significantly to ischemic brain injury after SAH and is mediated in part by decreased availability of NO.

Anti-oxidants prevent focal rat brain injury as assessed by induction of heat shock proteins (HSP70, HO-1/HSP32, HSP47) following subarachnoid injections of lysed blood

The initial aim of this study was to determine if the HSP70 (the main inducible heat shock protein), HO-1 (heme oxygenase-1, HSP32) and HSP47 (a collagen chaperone) stress proteins were induced in the same focal regions of rat brain following experimental subarachnoid hemorrhage (SAH). The next objective was to determine whether anti-oxidants prevented the stress gene expression in the focal regions. Lysed blood (150 microliter) was injected into the subarachnoid space of adult, female Sprague-Dawley rats via the cisterna magna. Animals were sacrificed 24 h later. Immunocytochemistry showed focal regions of stress gene induction in most animals (13/21), HSP70 and HO-1 proteins being expressed in neurons, microglia and astrocytes and HSP47 being expressed in microglia. Co-induction of the same three stress proteins was observed in focal areas in the striatum and cerebellum as well. In the 13 animals with focal regions of stress gene induction there were 8.1+/-1.8 foci in cortex, 5.5+/-0.9 foci in striatum, and 11.7+/-7.3 foci in cerebellum in the brain of each animal. The focal regions of stress gene induction varied in size from 200 micrometer to 7 mm in diameter. Systemic administration of the tirilazad-like anti-oxidants U101033E (n=8) and U74389G (n=7) completely blocked stress protein induction in focal brain regions normally produced by cisternal injections of lysed blood. There were fewer drug treated animals (0/15) with focal areas of stress gene induction compared to non-drug (13/21) treated animals following the cisternal lysed blood injections (p<0.01 using Fisher's probability test). This study shows that anti-oxidants prevent focal regions of injury as assessed by heat shock protein expression in a rat model of SAH.

Oxidative stress in the human brain after subarachnoid hemorrhage

OBJECT

The aim of this study was to verify the patterns of antioxidant enzymatic activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the human brain after subarachnoid hemorrhage (SAH) to verify whether an "oxidative stress situation" characterizes the brain response to subarachnoid bleeding.

METHODS

Forty samples of gyrus rectus or temporal operculum that were obtained during a surgical approach to anterior circulation aneurysms were used for this study. The activity of total SOD, GSH-Px, and the SOD/GSH/Px ratio (which expresses the balance between the production of hydrogen peroxides by dismutation of superoxide radicals and the scavenging potential) were calculated in each case. Twelve samples were obtained from patients who underwent surgery for unruptured aneurysms (control group); 13 samples were obtained during surgical procedures performed within 72 hours of SAH; and 15 samples were obtained during delayed surgical procedures (> 10 days post-SAH). Ten patients presented with clinical deterioration caused by arterial vasospasm. In both SAH groups, the mean total SOD activity was significantly higher than in the control group (p=0.029). The mean activity of GSH-Px did not differ significantly between the SAH and control groups (p=0.731). There was a significant increase in the SOD/GSH-Px ratio in both SAH groups, as compared with controls (p < 0.05). There was a significant correlation between the enzymatic activity and the clinical severity of the hemorrhage, with findings of lower values of SOD and, mainly, of the SOD/GSH-Px ratio in the poor-grade patients. The SOD/GSH-Px ratio was 2.14+/-0.44 in patients who presented with clinical vasospasm and 1.24+/-0.2 in cases without vasospasm.

CONCLUSIONS

The results of this study show an imbalance of the antioxidant enzymatic activities in the human brain after SAH. which is linked to the severity of the initial bleeding and possibly modified by the development of arterial vasospasm.

Acute vasoconstriction after subarachnoid hemorrhage

OBJECTIVE

Decreased cerebral blood flow (CBF) and cerebral ischemia occurring immediately after subarachnoid hemorrhage (SAH) may be caused by acute microvascular constriction. However, CBF can also be influenced by changes in intracranial pressure (ICP) and cerebral perfusion pressure (CPP). The goal of these experiments was to assess the significance of acute vasoconstriction after SAH and its relationship to changes in CBF, ICP, CPP, and extracellular glutamate concentrations.

METHODS

Three experiments were performed using the endovascular filament technique to produce SAH. In the first experiment, CBF, ICP, and CPP were measured for 60 minutes after SAH (n = 21) and were correlated with the 24-hour mortality rate. In the second experiment, rats undergoing SAH (n = 23) or a sham procedure (n = 7) were perfused 60 minutes after SAH for measurement of the circumference and wall thickness of the internal carotid and anterior cerebral arteries and correlation with CBF, ICP, and CPP. In the third experiment (n = 11), extracellular glutamate concentrations determined by hippocampal and cortical microdialysis and high performance liquid chromatography were correlated with physiological changes.

RESULTS

CBF reductions to less than 40% of baseline for 60 minutes after SAH predicted 24-hour mortality with 100% accuracy and were used to define "lethal" SAH. In contrast, ICP and CPP 60 minutes after SAH were not correlated with the mortality rate. The vascular circumference was significantly smaller in lethal than in sublethal SAH or sham-operated rats (P < 0.001). Vessel measurements were correlated with both CBF and hemorrhage size (P < 0.01). Extracellular glutamate concentration increased to 600% of baseline after lethal SAH in both hippocampus and cortex and was inversely correlated with CBF (r = 0.9, P < 0.001) but did not increase after sublethal SAH.

CONCLUSION

Acute vasoconstriction after SAH occurs independently of changes in ICP and CPP and is associated with decreased CBF, larger hemorrhage size, persistent elevations of extracellular glutamate, and poor outcome. Acute vasoconstriction seems to contribute directly to ischemic brain injury after SAH. Further evaluations of pharmacological agents with the potential to reverse acute vasoconstriction may increase CBF and improve outcome.

Time-course alterations of monoamine levels and cerebral blood flow in brain regions after subarachnoid hemorrhage in rats

To investigate the possible correlation between changes in monoaminergic neuronal activity and cerebral blood flow (CBF) in the same brain region after subarachnoid hemorrhage (SAH), monoamine levels were analyzed by both HPLC-ECD and fluorohistochemistry techniques, and CBF was measured by using colored microspheres. At the second day of SAH, significant and nonsignificant reductions in blood flow were seen in the examined brain regions with a marked increase in CBF appearing in the telencephalon and hypothalamus on the third day. Significant reductions of monoamine levels in most brain regions were also observed on the second day after SAH, whereas norepinephrine (NE) levels in midbrain increased to 1.5 times compared to the normal level. These reductions were sustained until the fourth day of SAH, although at the third day, serotonin (5-HT) and dopamine levels in the hippocampus and 5-HT levels in the cerebelium were significantly elevated. In fluorohistochemical studies, the fluoro-intensities of monoamines, particularly catecholamines, in the midbrain dorsal NE bundle were enhanced at the second day after SAH. These NE neurons originated from the A5 cell group close to the area where homologous blood was applied through the cisterna magna. The results obtained after SAH show an apparent correlation between changes in monoamine levels and CBF in norepinephrine (NE)-rich areas. These results suggest that SAH-induced neuronal dysfunctions, particularly with NE neurons, are caused not only by reductions of blood flow but also by hemorrhage.

Brain energy metabolism in the acute stage of experimental subarachnoid haemorrhage: local changes in cerebral glucose utilization

An experimental model was used to investigate acute alterations of cerebral metabolic activity in rats subjected to subarachnoid haemorrhage (SAH). Haemorrhages were produced in anaesthetized animals by injecting 0.3 ml of autologous, arterial nonheparinized blood into the cisterna magna. Control rats received subarachnoid injections of mock-cerebrospinal fluid to study the effect of sudden raised intracranial pressure, or underwent sham operation. Three hours after SAH rats were given an intravenous injection of [14C]-2-deoxyglucose. Experiments were terminated by decapitation, and the brains were removed and frozen. Regional brain metabolic activity was studied by quantitative autoradiography. In comparison with sham-operated controls, cerebral metabolic activity was diffusely decreased after SAH. Statistically significant decreases in metabolic rate were observed in 23 of 27 brain regions studied. Subarachnoid injections of mock-cerebrospinal fluid also produced depression of cerebral metabolic activity, but quantitatively these changes were not as pronounced and diffuse as in SAH rats. The present study shows that a widespread depression of brain metabolism occurs in the acute stage after experimental SAH and is probably secondary to the subarachnoid presence of blood itself and/or blood products.

Characterization of an anterior circulation rat subarachnoid hemorrhage model

BACKGROUND AND PURPOSE

Our aim was to demonstrate the feasibility of an angiographically controlled rat model for the study of macrocirculatory and microcirculatory changes of the anterior intracranial circulation after subarachnoid hemorrhage.

METHODS

Subarachnoid hemorrhage was induced by transorbital injection of 0.3 mL of nonheparinized autologous arterial blood into the chiasmatic cistern. Changes in regional cerebral blood flow were continuously recorded with the use of laser-Doppler flowmetry over the parietal cortex. Angiographic verification of middle cerebral artery diameter was performed by carotid catheterization at baseline and 2 days after injection of blood or artificial cerebrospinal fluid. We monitored intracranial and systemic blood pressure during and after injections.

RESULTS

Injection of artificial cerebrospinal fluid in the control group did not change the diameter of the middle cerebral artery. Injection of blood caused a significant arterial narrowing of 17.5%, from 0.37 +/- 0.04 mm to 0.31 +/- 0.04 mm after 2 days (P = .0001). In the control group regional cerebral blood flow decreased to 75.9 +/- 16.8% of preinjection control but quickly recovered to 99.7 +/- 19.4%. Intracranial pressure increased for 5 minutes after the injection to a maximum of 27.3 +/- 8.9 mm Hg, accompanied by a 10% decrease in mean arterial pressure. A fall in cerebral blood flow to 53.1 +/- 26.3% in blood-injected animals that recovered to only 80.7 +/- 16.9% of baseline values during the observation period of 30 minutes was noted. A peak intracranial pressure of 45.7 +/- 11.5 mm Hg occurred 2 minutes after injection with a decrease in mean arterial pressure of 13%, resulting in a markedly lower cerebral perfusion pressure than in the control group.

CONCLUSIONS

An angiographically controlled model of subarachnoid hemorrhage primarily involving the anterior circulation is feasible in the rat. The resulting narrowing of the middle cerebral artery reflects moderate vasospasm and will allow further microcirculatory studies with cranial windows.

Cerebrovascular sensory innervation involved in the development of cerebral vasospasm following a subarachnoid hemorrhage

Cerebral vasospasm following subarachnoid hemorrhage was induced in the squirrel monkey in order to evaluate the involvement of cerebrovascular sensory nerves in the development of the vasospasm. A unilateral surgical section of the trigeminal nerve at post- but not at pre-Gasserian level caused constriction of the major ipsilateral cerebral arteries. A pre- or postganglionic trigeminal lesion induced an increased glucose uptake globally without influencing the cerebral blood flow. Following a subarachnoid hemorrhage, the decrease in cerebral blood flow was similar of that seen in control animals, while post-ganglionically lesioned animals had an additional increase in glucose uptake. Intrathecal injection of gamma-globulin against substance P prevented the occurrence of vasospasm and the decrease in cerebral blood flow, while calcitonin gene-related peptide (CGRP) anti-gamma-globulin injection significantly reduced the resting vessel diameter and did not influence spasm development. It is concluded that a nervous reflex mechanism could underlie cerebral vasospasm. The cerebrovascular sensory nerves have both a peripheral and a central function. A peripheral or axon reflex mechanism exerts a tonic effect on the cerebral arteries. Central neurotransmission seems to be involved in the regulation of cerebral metabolism and possibly in the coordination of cerebral blood flow and glucose metabolism. CGRP could be the transmitter involved in a peripheral axon reflex and substance P might be the neurotransmitter conveying information to the brainstem vascular centers.

Behavioral deficits following experimental subarachnoid hemorrhage in the rat

To characterize some of the short-term and long-term functional consequences of subarachnoid hemorrhage (SAH) in rats, we employed a battery of well-characterized tests for assessment of acute and chronic behavioral and neurologic performances. Three groups of 10 rats (blood injected, mock CSF injected and sham-operated controls) were studied. During the acute stage, simple nonpostural somatomotor reflexes (pinna and corneal reflexes), simple postural responses (paw flexion, tail flexion, and head support), startle response, and postural functions (righting reflex) did not differ significantly between the experimental groups. Assessments of body weight, beam walking ability, and beam balancing revealed significant disturbances in blood-injected rats. This work demonstrates that this single-hemorrhage rodent model of SAH is associated with the induction of enduring neurologic and behavioral deficits. Because of the significant interspecies difference, a direct extrapolation of our results to humans may not be appropriate. However, we suggest that the observed behavioral and neurologic changes may parallel those seen in humans after SAH. Results reported here further confirm the rat model of SAH as a viable laboratory instrument for the study of the pathophysiology of SAH and provide normative values for the evaluation of new treatment modalities.

Cerebral blood flow and glucose metabolism in the squirrel monkey during the late phase of cerebral vasospasm

A double-isotope autoradiography technique was used to evaluate cerebral blood flow (CBF) and cerebral glucose metabolism (CMRglu) during the late phase of vasospasm in a squirrel monkey subarachnoid haemorrhage (SAH) model. Cisternal blood injections induced both global and focal changes in CBF and CMRglu six days following SAH, the timepoint of maximal late spasm in this model. There was a global decrease in CBF of about 30% accompanied by an increase in deoxyglucose uptake of about 50%. Four of seven animals also had foci with flow decreased to 40% of control and deoxyglucose uptake increased to 300% of control. There was an altered but still present interdependence between flow and metabolism post SAH.

Effect of spantide, a substance-P antagonist, on cerebral vasospasm in primates

Experimental SAH in the squirrel monkey induces an angiographically demonstrable late spasm of about 23% at six days post subarachnoid haemorrhage (SAH). The late spasm is associated with a generalized reduction in cerebral blood flow (CBF) of about 30%. Intracisternal administration of the substance P (SP) antagonist spantide two hours and three days post SAH significantly reduces the degree of late spasm and also decreases the degree of CBF reduction. The findings suggest that SP is involved in the development of both angiographical spasm and CBF changes post SAH.

Cerebrovascular changes following administration of gammaglobulins against substance P or calcitonin gene related peptide in monkey with subarachnoid haemorrhage

Cerebrovascular changes after intrathecal (ith) administration of gammaglobulins against substance P (SP) or calcitonin gene-related peptide (CGRP) were investigated before and following a simulated subarachnoid haemorrhage (SAH) in the squirrel monkey. The SAH was produced by injection of homologous blood into the interpeduncular fossa and the cisterna magna. The gammaglobulins were given both prior to the blood injections and daily in 5 days post-SAH. The effect of the gammaglobulins was examined by angiography pre-SAH and at 10 min and at 6 days post-SAH, i.e. the time points for maximal acute and late spasm in the present model. Cerebral blood flow (CBF) was measured under general anesthesia at day 6 post-SAH with an autoradiographic technique. Five of nine animals treated with CGRP antigammaglobulin died from respiratory failure. Four animals received SP antigammaglobulin and two control animals received normal globulin. SP antigammaglobulin per se had no effect on baseline arterial diameter, while CGRP antigammaglobulin significantly reduced the diameter of the arteries. SP antigammaglobulin prevented the occurrence of acute spasm and significantly reduced the degree of late spasm. Moreover, the reduction in CBF noted in the control SAH animals was significantly reduced. In contrast, CGRP antigammaglobulin treatment had no effect on the degree of spasm and did not cause any change in CBF as compared to controls. The finding that CGRP but not SP antigammaglobulin significantly reduces the arterial diameter in conjunction with our previous demonstration that a post-, but not preganglionic trigeminal lesion reduces the baseline arterial diameter, indicates that CGRP could be the transmitter involved in a peripheral axon reflex. The function of SP might be as a neurotransmitter conveying information to the brainstem. The transmitter role is supported by the effect of SP antigammaglobulin impairing SP containing neurons and, in that way, mimicking a bilateral trigeminal rhizotomy.

Novel pharmacologic therapies in the treatment of experimental traumatic brain injury: a review

Delayed or secondary neuronal damage following traumatic injury to the central nervous system (CNS) may result from pathologic changes in the brain's endogenous neurochemical systems. Although the precise mechanisms mediating secondary damage are poorly understood, posttraumatic neurochemical changes may include overactivation of neurotransmitter release or re-uptake, changes in presynaptic or postsynaptic receptor binding, or the pathologic release or synthesis of endogenous "autodestructive" factors. The identification and characterization of these factors and the timing of the neurochemical cascade after CNS injury provides a window of opportunity for treatment with pharmacologic agents that modify synthesis, release, receptor binding, or physiologic activity with subsequent attenuation of neuronal damage and improvement in outcome. Over the past decade, a number of studies have suggested that modification of postinjury events through pharmacologic intervention can promote functional recovery in both a variety of animal models and clinical CNS injury. This article summarizes recent work suggesting that pharmacologic manipulation of endogenous systems by such diverse pharmacologic agents as anticholinergics, excitatory amino acid antagonists, endogenous opioid antagonists, catecholamines, serotonin antagonists, modulators of arachidonic acid, antioxidants and free radical scavengers, steroid and lipid peroxidation inhibitors, platelet activating factor antagonists, anion exchange inhibitors, magnesium, gangliosides, and calcium channel antagonists may improve functional outcome after brain injury.

Effect of pre- and postganglionic lesioning of the trigeminal nerve on cerebral blood flow and glucose metabolism following a subarachnoid haemorrhage in the squirrel monkey

Simultaneous cerebral blood flow (CBF) and glucose metabolism (CMRglu) studies with a double isotope autoradiographic technique were applied to squirrel monkeys submitted to a unilateral pre- or postganglionic trigeminal lesion. The CBF values were not affected following a pre- or postganglionic lesion per se. In contrast, there was a global increase in the cerebral glucose uptake of about 50% as compared to controls following both kinds of lesions. Following a subarachnoid haemorrhage (SAH) 2-4 weeks after pre- or postganglionic trigeminal lesioning, there was a decrease in CBF similar to that seen in the control group. In the animals with a preganglionic lesion, the 50% increase in glucose uptake was not further augmented by a SAH and the increase in CMRglu was comparable to that found in control SAH animals. In the postganglionically lesioned monkeys, a SAH induced an additional increase in glucose uptake of about 50%. The findings suggest that the trigeminal system is involved in the regulation of cerebral metabolism via a brainstem centre.

Opposite alterations in cerebrospinal fluid uridine after severe cerebral ischemia or intrathecal blood injection

1. Rats which survived hypoglycemia by insulin, hypoxia by 10% O2, or ischemia by carotid ligation and hypotension to 40 mm Hg, evidenced no changes in cerebrospinal fluid (CSF) uridine. Animals which died soon after the above interventions or as a result of KCl-induced cardiac arrest had elevated CSF uridine concentrations. 2. Injection of whole blood or the soluble contents of lysed blood cells into the lateral ventricle of rats reduced CSF uridine to less than one-half normal at 24 hrs but values returned to normal 3 days later. Changes in hypoxanthine resembled those of uridine, but were less dramatic, whereas xanthine concentrations were largely unaltered. Intraventricular injection of plasma or saline did not alter CSF uridine. 3. It seems most likely that low CSF uridine concentrations previously reported in head injury patients may be secondary to the effects of blood cell contents in the cerebrospinal fluid, rather than responses to altered metabolism in neurons or glia cells.

Effect of prazosin on microvascular perfusion during middle cerebral artery ligation in the rat

The purpose of this study was to evaluate the effects of prazosin, an alpha 1-adrenoceptor antagonist, on morphometric indexes of the total and perfused cerebral microvascular bed 1 hour after middle cerebral artery (MCA) ligation in pentobarbital-anesthetized rats. We hypothesized that this agent would prevent catecholamine-induced vasoconstriction in the ischemic brain. Cerebral blood flow (CBF) was determined with 14C-iodoantipyrine, and the perfused microvascular bed was visualized using fluorescein isothiocyanate-dextran. MCA occlusion did not alter systemic hemodynamic or blood gas parameters. CBF averaged 29 +/- 15 (mean +/- SD) ml/min/100 g in the MCA-ligated cortex and 49 +/- 18 in the other examined brain regions. Prazosin did not significantly alter these CBF values, averaging 26 +/- 14 and 48 +/- 10, respectively. There were no significant regional differences in total capillaries/mm2 in either group. The percent of the capillaries/mm2 perfused (51 +/- 6%) was similar in the two groups in all examined regions except the ischemic cortex. In the MCA-ligated cortex, 22 +/- 8% of the capillary volume was perfused in comparison with 49 +/- 8% in the prazosin-treated group. Prazosin-treated rats had an increased percentage of their microvasculature perfused despite a similarly reduced CBF. Prazosin appeared to reduce diffusion distances in the ischemic cortex. This might be due to its alpha 1-adrenoceptor blocking activity.

Significance of "ultra-early" rebleeding in subarachnoid hemorrhage

Knowledge of the local incidence of aneurysm rupture permits the conclusion that almost every patient in the population of 933,800 persons served by the authors' institution who was stricken by this catastrophe and survived long enough to be transported was treated at this center (121 patients during 34 months). Of these, 9.1% were admitted late (greater than 72 hours after subarachnoid hemorrhage (SAH]; of the remaining cases, 94.5% were seen within 24 hours and 50% within 6 hours post-SAH. Of the 121 patients, 10% were neurologically devastated on arrival, a late operation was planned for 19%, and the earliest possible surgery and nimodipine administration was selected for 71%. In this latter group, 50% of the operations were begun within 24 hours and 76% within 48 hours post-SAH. Sixty percent of all mortality and morbidity could be linked to the initial aneurysm bleed. The remaining 40% could be ascribed to potentially avoidable causes of unfavorable outcome. No less than 9.6% of all patients admitted within 24 hours after SAH suffered from "ultra-early" rebleeding during transportation or preparation for operation. The mortality rate from such rebleeding was 7.4%, compared with the 9.1% combined mortality rate from complications and late ischemia.