Decrease in cerebral blood flow in rats after experimental subarachnoid hemorrhage: a new animal model

Anterior circulation mouse model of subarachnoid hemorrhage

A model of subarachnoid hemorrhage (SAH) first described in rats where blood is injected into the prechiasmatic cistern was adapted to mice. The hypothesis was that such an anterior circulation SAH model would produce vasospasm of greater severity and longer duration than other mouse models. The goal was to create a mouse model that could then be used in transgenic and knockout animals in order to further knowledge of SAH and vasospasm. A needle was inserted stereotactically into the prechiasmatic cistern and 100 microl autologous arterial blood injected over seconds (n=10). Effects were compared to injection of saline (n=10) or to sham operation (n=7). Monitoring of cerebral blood flow by laser Doppler showed a statistically similar decrease during injection in both groups. 7 days after SAH there was vasospasm of the middle and anterior cerebral arteries (51% reduction in MCA radius in SAH compared to saline-injected group, P<0.009, Student's t-test). In order to determine if SAH in this model was associated with neuronal injury, brains were examined for TUNEL and fluoro-jade-positive cells. 60% of SAH but not saline-injected mice exhibited TUNEL-positive cells in the cerebral cortex and 30% of the SAH but no saline-injected mice had fluoro-jade positive cells in the cortex, hippocampus and dentate gyrus. The model is simple to perform and may be useful for investigating the pathophysiology of SAH.

Prevention of cerebral vasospasm by local delivery of cromakalim with a biodegradable controlled-release system in a rat model of subarachnoid hemorrhage

OBJECT

One mechanism that contributes to cerebral vasospasm is the impairment of potassium channels in vascular smooth muscles. Adenosine triphosphate-sensitive potassium channel openers (PCOs) appear to be particularly effective for dilating cerebral arteries in experimental models of subarachnoid hemorrhage (SAH). A mode of safe administration that provides timed release of PCO drugs is still a subject of investigation. The authors tested the efficacy of locally delivered intrathecal cromakalim, a PCO, incorporated into a controlled-release system to prevent cerebral vasospasm in a rat model of SAH.

METHODS

Cromakalim was coupled to a viscous carrier, hyaluronan, 15% by weight. In vitro release kinetics studies showed a steady release of cromakalim over days. Fifty adult male Sprague-Dawley rats weighing 350-400 g each were divided into 10 groups and treated with various doses of cromakalim or cromakalim/hyaluronan in a rat double SAH model. Treatment was started 30 minutes after the second SAH induction. Animals were killed 3 days after treatment, and the basilar arteries were processed for morphometric measurements and histological analysis.

RESULTS

Controlled release of cromakalim from the cromakalim/hyaluronan implant at a dose of 0.055 mg/kg significantly increased lumen patency in a dose-dependent manner up to 94 +/- 8% (mean +/- standard error of the mean) of the basilar arteries of the sham group compared with the empty polymer group (p = 0.006). Results in the empty polymer group were not different from those in the SAH-only group, with a lumen patency of 65 +/- 12%. Lumen patencies of the cromakalim-only groups did not differ in statistical significance at low (64 +/- 9%) or high (66 +/- 7%) doses compared to the SAH-only group.

CONCLUSIONS

Treatment of SAH with a controlled-release cromakalim/hyaluronan implant prevented experimental cerebral vasospasm in this rat double hemorrhage model; this inhibition was dose-dependent. The authors' results confirm that sustained delivery of cromakalim perivascularly to cerebral vessels could be an effective therapeutic strategy in the treatment of cerebral vasospasm after SAH.

Effect of electrical stimulation of the cervical spinal cord on blood flow following subarachnoid hemorrhage

Object

Cervical spinal cord stimulation (SCS) increases global cerebral blood flow (CBF) and ameliorates cerebral ischemia according to a number of experimental models as well as some anecdotal reports in humans. Nonetheless, such stimulation has not been systematically applied for use in cerebral vasospasm. In the present study the authors examined the effect of cervical SCS on cerebral vasoconstriction in a double-hemorrhage model in rats.

Methods

Subarachnoid hemorrhage (SAH) was induced with 2 blood injections through an indwelling catheter in the cisterna magna. Spinal cord stimulation was applied 90 minutes after induction of the second SAH (Day 0) or on Day 5 post-SAH. Measurements of the basilar artery (BA) diameter and cross-sectional area and regional CBF (using laser Doppler flowmetry and 14C-radiolabeled N-isopropyl-p-iodoamphetamine hydrochloride) were obtained and compared between SAH and sham-operated control rats that did not receive SCS.

Results

At Day 0 after SAH, there were slight nonsignificant decreases in BA diameter and cross-sectional area (89 ± 3% and 81 ± 4%, respectively, of that in controls) in no-SCS rats. At this time point, BA diameter and crosssectional area were slightly increased (116 ± 6% and 132 ± 9%, respectively, compared with controls, p < 0.001) in SCS-treated rats. On Day 5 after SAH, no-SCS rats had marked decreases in BA diameter and cross-sectional area (64 ± 3% and 39 ± 4%, respectively, compared with controls, p < 0.001) and corrugation of the vessel wall. These changes were reversed in rats that had received SCS (diameter, 110 ± 9% of controls; area, 106 ± 4% of controls; p < 0.001). Subarachnoid hemorrhage reduced CBF at Days 0 and 5 post-SAH, and SCS increased flows at both time points, particularly in regions supplied by the middle cerebral artery.

Conclusions

Data in this study showed that SCS can reverse BA constriction and improve global CBF in this SAH model. Spinal cord stimulation may represent a useful adjunct in the treatment of vasospasm.

Increased expression of a proline-rich Akt substrate (PRAS40) in human copper/zinc-superoxide dismutase transgenic rats protects motor neurons from death after spinal cord injury

The serine-threonine kinase, Akt, plays an important role in the cell survival signaling pathway. A proline-rich Akt substrate, PRAS40, has been characterized, and an increase in phospho-PRAS40 (pPRAS40) is neuroprotective after transient focal cerebral ischemia. However, the involvement of PRAS40 in the cell death/survival pathway after spinal cord injury (SCI) is unclear. Liposome-mediated PRAS40 transfection was performed to study whether overexpression of pPRAS40 is neuroprotective. We further examined the expression of pPRAS40 after SCI by immunohistochemistry and Western blot using copper/zinc-superoxide dismutase (SOD1) transgenic (Tg) rats and wild-type (Wt) littermates. We then examined the relationship between PRAS40 and Akt by injection of LY294002, a phosphatidylinositol 3-kinase (PI3K) pathway inhibitor, or Akt inhibitor IV, a compound that inhibits Akt activation after SCI. Our data demonstrated that increased pPRAS40 resulted in survival of more motor neurons compared with control complementary DNA transfection. Phosphorylated PRAS40 increased in the Wt rats after SCI, whereas there was a greater and prolonged increase in the SOD1 Tg rats. Coimmunoprecipitation showed that binding of pPRAS40 with 14-3-3 increased 1 day after SCI in the Wt rats, whereas there was a significant increase in the Tg rats. The inhibitor studies showed that phospho-Akt and pPRAS40 were decreased after injection of LY294002 or Akt inhibitor IV. We conclude that an increase in pPRAS40 by transfection after SCI results in survival of motor neurons, and overexpression of SOD1 in the Tg rats results in an increase in endogenous pPRAS40 and a decrease in motor neuron death through the PI3K/Akt pathway.

Role of c-Jun N-terminal kinase in early brain injury after subarachnoid hemorrhage

The c-Jun N-terminal kinase (JNK) is induced by cerebral ischemia and injurious blood components acutely after subarachnoid hemorrhage (SAH). We hypothesized that inhibition of JNK will prevent damage to the neurovascular unit in the early brain injury period after SAH. Ninety-nine male SD rats (300-350 g) were randomly assigned to sham, SAH, and SAH treated with JNK inhibitor groups. SAH was induced by endovascular perforation. The JNK inhibitor SP600125 was administered intraperitoneally at 1 hr before and 6 hr after SAH. At 24 hr after SAH, we observed increased phosphorylation of JNK and c-Jun. Signs of neurovascular damage were observed in the hemorrhagic brains; these included the increases of aquaporin (AQP)-1 expression and brain water content as well as enhanced matrix metalloproteinase (MMP)-9 activity, vascular collagen IV loss, increased VEGF tissue level, and Evans blue extravasation. The appearances of cleaved caspase-3 expression, TUNEL-positive cells, and apoptotic morphology in cerebral tissues were associated with neurological deficit after SAH. JNK inhibition prevented c-Jun phosphorylation and suppressed AQP1, MMP-9, VEGF, and caspase-3 activation, with concomitant diminution of neuronal injury, blood-brain barrier preservation, reduced brain swelling, and improved neurological deficit in rats after SAH. This study demonstrates a multitude of beneficial effects of JNK inhibition, including protection of the neurovascular unit in early brain injury after SAH.

Effect of delayed cerebral vasospasm on cerebrovascular endothelin A receptor expression and function

Object

The key role in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH) is increasingly assigned to endothelin (ET)-1. Constriction of the cerebrovasculature by ET-1 is mainly mediated by the ETA receptor but is putatively altered during the development of cerebral vasospasm. Therefore, the aim in the present study was to characterize these alterations, with the emphasis on the ETA receptor.

Methods

Cerebral vasospasm was induced using the rat double-hemorrhage model and proven by perfusion weighted magnetic resonance imaging. Rats were killed on Day 5 after SAH, and immunohistochemical staining for ETA receptors was performed. The isometric force of basilar artery ring segments with (E+, control group) and without (E−, SAH group) endothelial function was measured. Concentration effect curves (CECs) for ET-1 were constructed by cumulative application in the absence and presence of the selective ETA receptor antagonist clazosentan (10−8 or 10−7 M).

Results

The CEC for E+ segments was significantly shifted to the left after SAH by a factor of 3.7, whereas maximum contraction was unchanged. In E− segments, the CECs were not shifted during cerebral vasospasm but the maximum contraction was significantly enhanced. The inhibitory potency of clazosentan yielded a pA2 value of 8.6 ± 0.2. Immunohistochemical staining of the smooth-muscle layer showed no significant increase of ETA receptor expression, but positive staining occurred in the endothelial space after SAH.

Conclusions

The present data indicate an enhanced contractile effect of the smooth-muscle ETA receptors in cases of cerebral vasospasm. The inhibitory potency of clazosentan on this contraction is increased. Furthermore, some evidence for an ETA receptor and an endothelium-dependent vasoactive effect after SAH is provided.

CHARACTERIZATION OF THE ENDOTHELIN-B RECEPTOR EXPRESSION AND VASOMOTOR FUNCTION DURING EXPERIMENTAL CEREBRAL VASOSPASM

OBJECTIVE

Several investigations suggest a key role of endothelin (ET) in the development of cerebral vasospasm (CVS). In the cerebrovasculature, physiologically ET-dependent constriction is mediated by the ET(A) receptor, whereas activation of the endothelial ET(B) receptor results in relaxation. However, existence of a contractile ET(B) receptor was postulated after subarachnoid hemorrhage (SAH), according to gene expression studies. The aim of the present investigation is, therefore, to characterize the function and the expression of the ET(B) receptor in the cerebrovasculature during CVS.

METHODS

CVS was induced in the rat double-hemorrhage model and assessed by perfusion-weighted magnetic resonance imaging scans. Rats were sacrificed on Days 3 and 5 after SAH, and immunohistochemical staining for ET(B) receptors was performed. Isometric force of basilar artery ring segments with (E+) and without (E-) endothelial function was measured. Concentration effect curves for the ET(B) receptor agonist, sarafotoxin 6c, were constructed by cumulative application in segments under resting tension and after precontraction.

RESULTS

Immunoreactivity for the ET(B) receptor was observed exclusively in the endothelium and was not significantly altered after SAH. Under resting tension, sarafotoxin 6c did not induce significant contraction in E+ or E- segments. After precontraction, a significant relaxation was induced by sarafotoxin 6c administration in sham-operated rats (mean maximum effect, 103 +/- 10%), which decreased time dependently after SAH (Day 3, 68 +/- 3%; Day 5, 42 +/- 3%). Endothelium-dependent relaxation induced by acetylcholine, however, was not significantly reduced.

CONCLUSION

The present investigation provides evidence for the loss of the ET(B) receptor-mediated vasomotor function after SAH. Thus, antagonism of the ET(B) receptor may be undesirable for the treatment of CVS.

PERSISTENCE OF THE NITRIC OXIDE-DEPENDENT VASODILATORPATHWAY OF CEREBRAL VESSELS AFTEREXPERIMENTAL SUBARACHNOID HEMORRHAGE

OBJECTIVE

Efficiency of the treatment of cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH) by interfering with the nitric oxide-cyclic guanosine monophospate (cGMP) pathway seems to be inconsistent. So far, it remains unclear whether or not insufficient access to the drugs or impaired reactivity of the vessels is responsible for this inconsistency. Therefore, the aim of the present investigation was to characterize this pathway on cerebral arteries during CVS.

METHODS

CVS was induced using the rat double hemorrhage model and was determined by magnetic resonance perfusion weighted imaging. Rats were sacrificed on Day 3 and Day 5 after SAH. Immunohistochemical staining of the basilar artery for endothelial nitric oxide synthases and the alpha- and beta-subunits of the soluble guanylate cyclase was performed. Basilar artery ring segments on Day 5 were used for measurement of isometric force. Concentration effect curves for acetylcholine, sodium nitroprusside, and 8-bromo-cGMP were constructed and compared by maximum effect and pD2.

RESULTS

The immunohistochemical expression of endothelial nitric oxide synthase was comparable in all groups. The soluble guanylate cyclase alpha- and beta-subunits were significantly diminished on Day 3, but recovered by Day 5. The relaxation attributable to acetylcholine and 8-bromo-cGMP was virtually identical in controls and during CVS. Relaxation attributable to sodium nitroprusside, however, was significantly enhanced after SAH (maximum effect, control: 88 +/- 12%; Day 5: 117 +/- 26%).

CONCLUSION

The present investigations suggest the persistence of endothelium-, nitric oxide-, and cGMP-dependent relaxation during CVS. Therefore, the treatment of CVS interfering with this pathway seems not to be limited by alterations inside the vessel wall.

Cortical cooling induces conditioned consumption reduction in male rats

Previous studies have shown that male rats acquire a conditioned reduction in consumption of a sucrose solution when consumption of that taste solution is followed by cooling the caudate putamen. Because the shaft of the cold probe was not insulated, this cooling also included the cortex and meninges overlying the caudate putamen. When cooling the meninges was eliminated as a factor, the conditioned consumption reduction was weaker but it was not abolished. This suggests that meninges cooling contribute to the conditioned consumption reduction induced when all three structures are cooled, but it is not sufficient. Five experiments were designed to determine whether cooling the cortex also contributes. In the first experiment, the temperature of the cortex and meninges overlying the caudate putamen was measured during cooling. In the following three experiments the ability of male rats to acquire a conditioned consumption reduction was determined after pairing a sucrose solution with cooling the cortex and meninges overlying the caudate putamen, cooling the cortex with and without cooling the dura meninges membrane, and cooling the cortex with and without cooling the entire meninges. When the cortex was cooled without cooling the caudate putamen, dura, or entire meninges, a conditioned consumption reduction was acquired. The last experiment demonstrated that contingent pairing of sucrose and cortical cooling was required to obtain consumption reduction. These results clearly indicate that cortical cooling contributes to the acquisition of conditioned consumption reduction induced when the caudate putamen and overlying cortex and meninges are cooled. Two hypotheses are suggested to account for the ability of neural cooling to act as an unconditioned stimulus in the conditioned consumption reduction paradigm: (1) neuronal inactivation produces physiological changes that can serve as unconditioned stimuli and (2) cooling itself produces physiological changes that can serve as unconditioned stimuli.

Molecular mechanisms of early brain injury after subarachnoid hemorrhage

OBJECTIVES

Increasing body of experimental and clinical data indicates that early brain injury after initial bleeding largely contributes to unfavorable outcome after subarachnoid hemorrhage (SAH). This review presents molecular mechanisms underlying brain injury at its early stages after SAH.

METHODS

PubMed was searched using term 'subarachnoid hemorrhage' and key words referring to molecular and cellular pathomechanisms of SAH-induced early brain injury.

RESULTS

The authors reviewed intracranial phenomena and molecular agents that contribute to the early development of pathological sequelae of SAH in cerebral and vascular tissues, including cerebral ischemia and its interactions with injurious blood components, blood-brain barrier disruption, brain edema and apoptosis.

DISCUSSION

It is believed that detailed knowledge of molecular signaling pathways after SAH will serve to improve therapeutic interventions. The most promising approach is the protection of neurovascular unit including anti-apoptosis therapy.

Time Course in the Development of Cerebral Vasospasm after Experimental Subarachnoid Hemorrhage: Clinical and Neuroradiological Assessment of the Rat Double Hemorrhage Model

OBJECTIVE

The "double hemorrhage" model in the rat is frequently used to simulate delayed cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH) in humans. However, an exact neurological and angiographic characterization of the CVS is not available for this model so far and is provided in the present investigation. Additionally, perfusion weighted imaging (PWI) at 3 tesla magnetic resonance (MR) tomography was implemented to assess the reduction in cerebral blood flow (CBF).

METHODS

In a prospective, randomized setting CVS was induced by injection of 0.2 ml autologous blood twice in the cisterna magna of 45 male Sprague-Dawley rats. The surviving animals were examined on Days 2, 3, 5, 7 and 9 and compared to a sham operated control group (n = 9). Rats were neurologically graded between 0 and 3, followed by MRI and selective digital subtraction angiography (DSA). The relative CBF was set in relation to the perfusion of the masseter muscle.

RESULTS

The neurological state was significantly worsened on Day 2 (Grade 3), 3 (Grade 3), and 5 (Grade 2) (medians). The relative CBF/muscle BF ratio (2.5 +/- 0.8 (SAH) versus 9.2 +/- 1.3 (sham) (mean +/- SEM) and the basilar artery (BA) diameter (0.15 +/- 0.02 mm (SAH) versus 0.32 +/- 0.01 mm (sham) were significantly decreased on Day 5. Correlation between relative CBF/muscle BF ratio and BA diameter was 0.70.

CONCLUSION

A valid and reproducible CVS simulation was proven by neurological score, DSA, and PWI on Day 5. Furthermore, our data demonstrate the practicability and validity of MR PWI for the monitoring of CVS in a rat SAH model.

Assessment of vasospasm in experimental subarachnoid hemorrhage in rats by selective biplane digital subtraction angiography

Although the rat subarachnoid hemorrhage model is well established in vasospasm research, the angiographic evaluation is difficult due to the animal's small size. For this reason, the aim of the study was to develop a standardized angiographic examination technique without additional complex equipment. Under general anesthesia, 11 Sprague-Dawley rats underwent selective cerebral digital subtraction angiography using a 0.3 mm focal spot and a 2.0-fold linear magnification. Five animals had experimental subarachnoid hemorrhage according to the "double-hemorrhage" model. Comparison with the intraarterial tip of the microcatheter enabled calibration of the vessel lumen. The diameter of the normal basilar artery (n=6) was 0.34+/-0.03 mm (mean+/-SD), whereas delayed vasospastic constriction (mean 6.2 days) caused a reduction in diameter of 32.4% (0.23+/-0.09 mm) as well as impaired collateral blood flow via the posterior communicating artery and anterior spinal artery. Histological examination of sections stained with hematoxylin and eosin under a light microscope confirmed vasospasm. In conclusion, biplane digital subtraction angiography allows precise and reliable evaluation of arterial diameter reduction and hemodynamic parameters in a rat vasospasm model. However, further investigation is required for assessment of vasoactive drugs, e.g., endothelin receptor antagonists.

Signaling pathways for early brain injury after subarachnoid hemorrhage

Few studies have examined the signaling pathways that contribute to early brain injury after subarachnoid hemorrhage (SAH). Using a rat SAH model, the authors explored the role of vascular endothelial growth factor (VEGF) and mitogen-activation protein kinase (MAPK) in early brain injury. Male Sprague-Dawley rats (n = 172) weighing 300 to 350 g were used for the experimental SAH model, which was induced by puncturing the bifurcation of the left anterior cerebral and middle cerebral arteries. The blood-brain barrier (BBB), brain edema, intracranial pressure, and mortality were evaluated at 24 hours after SAH. The phosphorylation of VEGF and different MAPK subgroups (ERK1/2, p38, and JNK) were examined in both the cortex and the major cerebral arteries. Experimental SAH increased intracranial pressure, BBB permeability, and brain edema and produced high mortality. SAH induced phosphorylation of VEGF and MAPKs in the cerebral arteries and, to a lesser degree, in the cortex. PP1, an Src-family kinase inhibitor, reduced BBB permeability, brain edema, and mortality and decreased the phosphorylation of VEGF and MAPKs. The authors conclude that VEGF contributes to early brain injury after SAH by enhancing the activation of the MAPK pathways, and that the inhibition of these pathways might offer new treatment strategies for SAH.

Hypothalamic neuropeptide release after experimental subarachnoid hemorrhage: in vivo microdialysis study

OBJECTIVES

As evidence exists about independent regulation of peripheral and central release of the vasoactive and natriuretic neuropeptides arginine-vasopressin (AVP) and oxytocin (OXT), we investigated their release patterns following subarachnoid hemorrhage (SAH).

MATERIALS AND METHODS

After injection of 0.1 ml arterial blood or saline into the great cistern of 33 Wistar rats, AVP and OXT levels were measured in blood and by microdialysis in the hypothalamic supraoptic (SON) and paraventricular nucleus (PVN). For statistical analysis, the analysis of variance (ANOVA) was used with Tukey HSD post hoc ANOVA tests to determine specific group differences.

RESULTS

Plasma AVP and OXT peaked 2 h after SAH (P < 0.05), and normalized at 4 h. In the SON, both AVP and OXT peaked 4 h after SAH (P < 0.05). In the PVN, AVP increased in both groups (P < 0.05), while no OXT release occurred. By the sham group, any effect of experimental procedure was excluded.

CONCLUSIONS

The SAH-specific central neuropeptide release, which exceeded peripheral release and continued longer, may contribute to pathophysiological events following SAH.

Cerebral angiogenesis and expression of VEGF after subarachnoid hemorrhage (SAH) in rats

Subarachnoid hemorrhage (SAH) leads to the development of vasospasm in which endothelin-1 plays a very important role. The effect of its vasoconstricting action is hypoxia of the nervous tissue, which stimulates the release of growth factors. Vascular endothelial growth factor (VEGF) released in excessive amounts from hypoxically altered cerebrovascular endothelial cells is the most potent angiogenic factor and may enhance angiogenesis after SAH. If endothelin-1 is mainly responsible for vasospasm after SAH, it is possible that early administration of endothelin converting enzyme inhibitor or endothelin receptor antagonist may protect neurons against. The aim of the study was to establish whether prolonged vasospasm and endothelial cell hypoxia stimulate VEGF expression and, in consequence, promote angiogenesis in the central nervous system after subarachnoid hemorrhage. Investigations were also performed to determine whether the administration of phosphoramidon, an endothelin-converting enzyme (ECE) inhibitor, and BQ-123, an endothelin receptor ET(A) antagonist, suppresses angiogenesis and VEGF expression. Experiments were carried out in male Wistar rats injected with phosphoramidon or BQ-123 into the cisterna magna following the induction of subarachnoid hemorrhage. The brains were removed 48 h after the hemorrhage for histopathological and immunohistochemical examinations of VEGF expression and angiogenesis in the cerebral hemispheres, brainstem, and cerebellum. Statistical analysis was performed using nonparametric Wilcoxon test (P<0.05). The results obtained have shown for the first time a close correlation between endothelial hypoxia after SAH in cerebral microvessels and enhanced angiogenesis. There is also an increase in VEGF expression in cerebral vessels and neurons within the cerebral hemispheres, brainstem, and cerebellum. The administration of phosphoramidon or BQ-123 has been found to inhibit angiogenesis. Angiogenesis in the chronic phase of SAH-induced vasospasm is the result of prolonged narrowing of vessels due to excessive secretion of endothelin by damaged endothelial cells. Present results obtained indicate that it is possible to reduce or prevent the late effects of SAH, i.e., neuronal hypoxia and cerebral edema, through the inhibition of endothelin-1 induced vasospasm.

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.

Signal transduction pathways in cerebral vasospasm

Cerebral vasospasm is a deadly complication following the rupture of intracranial aneurysms. The time course of cerebral vasospasm is unique in that it is slow developing, usually takes 4-7 days to peak, but lasts up to 2-3 weeks, and is resistant to most known vasodilators. These special features make cerebral vasospasm the most important determinant in the outcome of patients suffering subarachnoid hemorrhage. The available treatment strategies include mechanical dilation of spastic cerebral arteries (angioplasty) and non-selective vasodilatation such as by Ca(2+) channel blockers. One new development in the experimental treatment of cerebral vasospasm is the looming target of signaling pathways. Understanding vasospastic signals in cerebral arteries might offer a new avenue for selective treatment of cerebral vasospasm in the future.

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.

A new experimental model in rats for study of the pathophysiology of subarachnoid hemorrhage

A new experimental model of subarachnoid hemorrhage (SAH) in rats is described. A needle was stereotaxically placed in the prechiasmatic cistern and 300, 250 or 200 microl of blood was injected manually, keeping the intracranial pressure (ICP) at the mean arterial blood pressure (MABP) level. An acceptable mortality was observed only after injection of 200 microl of blood. In this group, MABP and ICP increased immediately after SAH, but soon approached baseline levels. The subarachnoid blood was mainly distributed in the basal cisternal system and its estimated volume was about 95% of the amount injected. This new model resembles clinical SAH, is very reproducible, easy to use and seems to be a suitable model for studies of the pathophysiology of SAH.

The meninges contribute to the conditioned taste avoidance induced by neural cooling in male rats

After consumption of a novel sucrose solution, temporary cooling of neural areas that mediate conditioned taste avoidance can itself induce conditioned avoidance to the sucrose. It has been suggested that this effect is either a result of inactivation of neurons in these areas or of cooling the meninges. In a series of studies, we demonstrated that cooling the outer layer of the meninges, the dura mater, does not contribute to the conditioned taste avoidance induced by cooling any of these areas. The present experiments were designed to determine whether the inner layers of the meninges are involved. If they are involved, then one would expect that cooling locations in the brain that do not mediate conditioned taste avoidance, such as the caudate putamen (CP), would induce conditioned taste avoidance as long as the meninges were cooled as well. One also would expect that cooling neural tissue without cooling the meninges would reduce the strength of the conditioned taste avoidance. Experiment 1 established that the temperature of the neural tissue and meninges around the cold probes implanted in the CP were cooled to temperatures that have been shown to block synaptic transmission. Experiment 2 demonstrated that cooling the caudate putamen and overlying cortex and meninges induced conditioned taste avoidance. In experiment 3, a circle of meninges was cut away so that the caudate putamen and overlying cortex could be cooled without cooling the meninges. The strength of the conditioned taste avoidance was substantially reduced, but it was not entirely eliminated. These data support the hypothesis that cooling the meninges contributes to the conditioned taste avoidance induced by neural cooling. They also allow the possibility that neural inactivation produces physiological changes that can induce conditioned taste avoidance.

Impairment of autoregulatory vasodilation by NAD(P)H oxidase-dependent superoxide generation during acute stage of subarachnoid hemorrhage in rat pial artery

This study assessed the mechanism(s) by which the autoregulatory vasodilation of rat pial artery in response to acute hypotension during the acute phase of subarachnoid hemorrhage (SAH) was markedly blunted. Increased superoxide production from the cerebral vessels in response to NAD(P)H at 24 hours after SAH + NG-nitro-l-arginine methyl ester (l-NAME) (10 mg/kg) was inhibited by intracisternal administration of a tyrosine kinase inhibitor genistein (10 micromol/L) and Rac inhibitor Clostridium difficile toxin B (1 ng/mL) and a flavoenzyme inhibitor diphenyleneiodonium (10 micromol/L). The expression of gp91phox was enhanced by SAH + l-NAME from 12 to 24 hours, which was inhibited by genistein and toxin B, but not the p22phox. Increased membrane translocation of Rac after SAH + l-NAME was attenuated by both genistein and toxin B, whereas increased tyrosine kinase activity was blocked by genistein, but not by toxin B. The blunted autoregulatory vasodilation to acute hypotension was effectively recovered by genistein and C. difficile toxin B as well as by diphenyleneiodonium. In conclusion, SAH during acute stage causes an increase in NAD(P)H oxidase-dependent superoxide formation in cerebral vessels, which is due to activation of tyrosine phosphorylation-dependent increased expression of gp91phox mRNA and translocation of Rac protein, thereby resulting in a significant reduction of autoregulatory vasodilation.

Influence of the type and rate of subarachnoid fluid infusion on lethal neurogenic pulmonary edema in rats

In patients who experience sudden death from spontaneous subarachnoid hemorrhage, more than 90% present with acute pulmonary edema. The underlying pathogenesis of this complication is poorly understood. In addition, the specific role of the extravasated blood products and the associated elevation in intracranial pressure leading to the systemic and pulmonary effects during subarachnoid hemorrhage are not well established. The authors tested a new model of acute and severe subarachnoid hemorrhage comparing fresh whole autologous blood (n = 20) with 5% albumin (n = 19) injected at two different rates (35 seconds versus 24 minutes) into the cisterna magna of anesthetized, mechanically ventilated rats. Cerebral and systemic hemodynamics and the corresponding pulmonary function were evaluated. The type of fluid injected had no influence on survival or hemodynamic and respiratory parameters. Rapid infusion of either blood or albumin (n = 14) produced an acute and transient rise in intracranial pressure (37.9 +/- 3.5 mm Hg) associated with systemic hypertension and increased cerebral perfusion pressure that was sustained in survivors but not in nonsurvivors. Slow infusion (n = 23) produced a more progressive increase in intracranial pressure to 31.2 +/- 7.1 mm Hg with a parallel and sustained increase of systemic blood pressure and preserved cerebral perfusion pressure in survivors, but produced a pattern of more severe hypertension followed by hypotension in nonsurvivors. Sixty-four percent of animals (rapid infusion) and 48% of animals (slow infusion) survived the challenge and presented no pulmonary alterations. In contrast, nonsurviving rats developed reduced lung compliance and gas exchange, an increased alveolar-arterial protein concentration ratio (0.36 +/- 0.02 versus 0.17 +/- 0.03 in survivors; P <.0001), and increased lung weight (5.7 +/- 0.3 g versus 2.0 +/- 0.1 g; P <.0001), demonstrating a fulminant increased permeability pulmonary edema, leading to death within one hour. These results indicate that the chosen rapid- and slow-injection rates resulted in a similar death rate of 50%. Mortality was similar for blood and albumin administration, pulmonary edema occurred in nonsurvivors in both the rapid- and slow-injection groups, and pulmonary edema is associated with more severe hypertension in the slow-injection group. Furthermore, these results suggest that the development of neurogenic pulmonary edema that is characterized by an acutely increased capillary permeability to proteins is independent of the degree of intracranial pressure increase or the type of fluid administrated.

Morphological changes of cerebral arteries in a canine double hemorrhage model

Cerebral vasospasm is a major cause of morbidity and mortality in patients suffering from subarachnoid hemorrhage (SAH). Despite numerous studies, the pathogenesis of this deadly disorder is not clearly understood. Alterations in endothelial cells are a distinct morphological feature of cerebral vasospasm and some recent studies suggest that apoptosis might play a role in the cells' death. The goal of the present study is to examine the time course of apoptosis in endothelial cells of spastic cerebral arteries following experimental subarachnoid hemorrhage. Fifteen dogs were used in the present study. Twelve of them were divided into three groups (four per group) and subjected to a double-hemorrhage method of SAH. Following SAH, groups were sacrificed respectively on days 3, 5, and 7. Three dogs served as controls without blood injection. The basilar arteries were studied with the transmission electron microscopy and with angiography. Angiographic vasospasm began on day 3 and peaked on day 7. In morphologic studies, control dogs did not demonstrate apoptotic-like changes in endothelial cells of the basilar arteries. Beginning with day 3, apoptotic-like changes were noted in endothelial cells and consisted of condensation of peripheral nuclear chromatin, blebbing of the cell membrane, and condensation of the cytoplasm. Such changes progressed with time and were maximally developed by day 7. This is the first study that demonstrates the time course of apoptotic-like changes in the endothelial cells in the vasospastic basilar artery. Apoptosis might play an important role in the pathogenesis of vasospasm.

Preliminary study of the effects of caspase inhibitors on vasospasm in dog penetrating arteries

This preliminary study was undertaken to explore the possible protective effect of caspase inhibitors Z-VDVAD-FMK and Z-DEVD-FMK in apoptosis and vasospasm in penetrating arteries during cerebral vasospasm. Experimental subarachnoid hemorrhage (SAH) was induced in 16 dogs by an intracisternal injection of autologous arterial blood (0.4 ml/kg) on Day 0 and Day 2. The dogs were then randomly divided into four groups: control-SAH, vehicle-control, and two treatment groups. In the treatment groups, caspase inhibitors (10 microM) were intracisternally injected each day beginning on Day 2 until Day 6. Effects of the inhibitors were analyzed utilizing angiography, the clinical status of the dogs (activity, appetite, and neurological deficits), and transmission electron microscopy of the penetrating arteries. All the dogs were sacrificed on Day 7. In control-SAH and vehicle-control groups, severe angiographic vasospasm, poor clinical status, and penetrating vasospasm were registered in all the dogs. In the treatment groups, all the dogs developed angiographic vasospasm and vasospasm in penetrating arteries, however, with benign clinical statues. The occurrence of apoptosis in endothelial cells was reduced by caspase-2 but not by caspase-3 inhibitor. Caspase inhibitors failed to prevent vasospasm either in major or in penetrating arteries. The improvement of clinical scores by the caspase inhibitors may be related to their protection of the endothelial cells. Further investigations using more rigorous clinical scoring system and quantitative information on the degree of apoptosis in the vessels, as well as in the brain parenchyma are recommended.

20-HETE contributes to the acute fall in cerebral blood flow after subarachnoid hemorrhage in the rat

This study examined the effects of blocking the formation of 20-hydroxyeicosatetraenoic acid (20-HETE) on the acute fall in cerebral blood flow after subarachnoid hemorrhage (SAH) in the rat. In vehicle-treated rats, regional cerebral blood flow (rCBF) measured with laser-Doppler flowmetry fell by 30% 10 min after the injection of 0.3 ml of arterial blood into the cisterna magna, and it remained at this level for 2 h. Pretreatment with inhibitors of the formation of 20-HETE, 17-octadecynoic acid (17-ODYA; 1.5 nmol intrathecally) and N-hydroxy-N'-(4-butyl-2-methylphenyl)formamidine (HET0016; 10 mg/kg iv), reduced the initial fall in rCBF by 40%, and rCBF fully recovered 1 h after induction of SAH. The concentration of 20-HETE in the cerebrospinal fluid rose from 12 +/- 2 to 199 +/- 17 ng/ml after SAH in vehicle-treated rats. 20-HETE levels averaged only 15 +/- 11 and 39 +/- 13 ng/ml in rats pretreated with 17-ODYA or HET0016, respectively. HET0016 selectively inhibited the formation of 20-HETE in rat renal microsomes with an IC(50) of <15 nM and human recombinant CYP4A11, CYP4F2, and CYP4F3 enzymes with an IC(50) of 42, 125, and 100 nM, respectively. These results indicate that 20-HETE contributes to the acute fall in rCBF after SAH in rats.

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.

Endoscopic technique: a new model of subarachnoid hemorrhage in rats

It has become increasingly evident that the pathophysiology of cerebral vasospasm following subarachnoid hemorrhage (SAH) which described the ischemic consequences of cerebral arterial constriction is complex and multifactorial. In an attempt to study cerebral vasospasm, numerous investigators have used experimental animal models that resemble cerebral vasospasm in humans. No ideal model for SAH has been found as yet, and hence the quest for such a model continues. We developed an endoscopic technique that permits a direct vision of internal carotid artery and puncturing the artery to provoke SAH. This model will closely reflect the clinical setting of an aneurysm rupture. The onset of SAH was characterized by a sudden decrease of cerebral blood flow (CBF) and cerebral blood volume (CBV) by at least 40% in the first 20 min. Following this initial drop, there was an increase in the CBF and the CBV, however, they remained significantly below the base line values, at the end of 1 h. This study describes a new model of SAH in rat that simulates the clinical phenomenon of ruptured intracranial aneurysm that also produces cerebral vasospasm.

The role of the dura in conditioned taste avoidance induced by cooling the area postrema of male rats

Experiments were designed to assess the contribution of the dura mater to the formation of conditioned taste avoidance induced by cooling the area postrema. The results of the first experiment verified that the temperature of the dura showed a temperature gradient at various distances from the tip of the cold probe. In the second and third experiments, a circle of dura was cut away so that different amounts of the area postrema could be cooled without cooling the overlying dura. Cooling the dura plus the area postrema did not produce a stronger avoidance than just cooling the area postrema. In the fourth experiment, the cerebellar cortex was cooled with and without cooling the dura. Cooling the cerebellar cortex produced conditioned taste avoidance, and cooling the dura plus the cerebellar cortex did not produce a stronger avoidance. Taken together, these results suggest that cooling the dura mater does not contribute to the conditioned taste avoidance induced by cooling the area postrema. The results of the fifth experiment showed that cooling the area postrema produced a stronger conditioned taste avoidance than cooling the cerebellar cortex. It is suggested that the avoidance induced by cooling both of these structures is the result of physiological changes occurring when neurons in these structures are inactivated and when the subdural meninges are cooled. Furthermore, these changes are more severe when the area postrema is cooled.

Morphological changes of cerebral penetrating arteries in a canine double hemorrhage model

BACKGROUND

Morphological presentations of cerebral vasospasm, such as dystrophy and desquamation of endothelial cells, corrugation of the internal elastic layer, and necrotic changes in smooth muscle cells, are well defined in large cerebral arteries. This study was undertaken to examine pathological changes in cerebral penetrating arteries in a canine double hemorrhage model.

METHODS

Eighteen mongrel dogs were subjected to an autologous arterial blood (0.4 mL/kg) injection into the cisterna magna on day 0 and day 2 after withdrawal of an equivalent amount of cerebrospinal fluid. Angiogram was performed on day 0 before the blood injection and on the day the dogs were sacrificed. The dogs were divided into four groups: control (day 0) (n = 4), hemorrhage and sacrificed on day 3 (n = 4), day 5 (n = 5), and day 7 (n = 5). The penetrating arteries were removed and found to be spastic on days 3, 5, and 7, but not in the control group.

RESULTS

Endothelial dystrophy and partial desquamation were recorded in all dogs sacrificed on days 5 and 7. Condensation of chromatin, blebbing of the membrane, and condensation of cytoplasm were identified in many endothelial cells, features that are consistent with apoptosis. The morphological changes in the penetrating arteries were more pronounced on days 5 and 7.

CONCLUSIONS

Vasospasm occurred in cerebral penetrating arteries in a canine double hemorrhage model. The morphological change in penetrating arteries, especially apoptosis in endothelial cells, is consistent with an early phase of vasospasm. Vasospasm in a penetrating artery may contribute to the cerebral ischemia that occurs during vasospasm.

Experimental models of subarachnoid hemorrhage in the rat: a refinement of the endovascular filament model

The rat endovascular filament model has been utilized to study subarachnoid hemorrhage (SAH). Because the severity of the hemorrhage with this model has proven difficult to modulate, we attempted to vary the hemorrhage by modifying filament size, and compared this model to the blood injection method with regards to acute physiological responses and hemorrhage size. SAH was achieved using either a 3-0 or 4-0 filament, or by injecting 0.3 cc of autologous blood into the cisterna magna. Peak ICP elevations were lowest in the 4-0 filament group. CBF decreased acutely and rose from its nadir in all three models with the injection model demonstrating the earliest recovery. In the injection group, mean arterial blood pressure rose acutely and remained elevated, whereas in the 3-0 group, MABP rose transiently and in the 4-0 group it did not rise significantly. Histologically, there was less subarachnoid blood in the 4-0 group vs. the injection or 3-0 groups and a different distribution of blood in the two experimental models. Varying filament size provides a method to modulate the severity of SAH in the filament model. In addition, the rat endovascular filament and blood injection models produce different distribution of blood and physiological responses.

Apoptosis of endothelial cells in vessels affected by cerebral vasospasm

BACKGROUND

Cerebral vasospasm after subarachnoid hemorrhage is a prolonged contraction that leads to cerebral ischemia or infarction. Morphological studies of cerebral arteries during vasospasm have shown extensive necrosis of smooth-muscle cells and desquamation and dystrophy of endothelial cells. The mechanism of cellular death is unknown.

METHODS

We report an observation of apoptotic changes in the cerebral arteries of a patient who died after suffering severe cerebral vasospasm caused by aneurysmal rupture. Subarachnoid hemorrhage and cerebral vasospasm were confirmed by computed tomography scanning and angiogram. Histological and immunohistological examinations for apoptosis were performed in cerebral arteries. For control, the arteries from another patient, who died of trauma without head injury, were used.

RESULTS

Corrugation of the internal elastic lamina and increased amounts of connective tissue was demonstrated by light microscopy. Apoptotic changes, characterized by condensation of chromatin of the nucleus and detachment from the basal membrane, were found on transmission electron microscopy in endothelial cells. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling reaction revealed positive staining of the nuclei of the endothelial cells.

CONCLUSIONS

This study demonstrates that apoptosis occurred in the cerebral arteries in a patient who died of cerebral vasospasm. The possible role of apoptosis in cerebral vasospasm is discussed.

Induction of heat shock protein 70 in the rat brain following intracisternal infusion of autologous blood: evaluation of acute neuronal damage

OBJECT

Investigation into a potential treatment for the acute period following onset of spontaneous subarachnoid hemorrhage (SAH) is hampered by the lack of a standardized experimental model. For that purpose the authors elaborated on a small-animal model in which computer-controlled intracisternal blood infusion is used and investigated whether this model can reliably reproduce acute neuronal injury after SAH.

METHODS

Whole autologous blood (blood-infused group) or isotonic saline (control group) was infused into the cisterna magna or olfactory cistern of rats. The infusions decreased exponentially during a 5-minute period. Throughout the infusion period, intracranial pressure (ICP) was monitored. Neuronal injury was quantified by observing tissue immunoreactivity to a 70-kD heat shock protein (HSP70) and comparing this with the tissue's reaction to hematoxylin and eosin staining. On Days 1, 3, and 5, the CA1, CA3, and dentate gyrus regions of the hippocampus were analyzed, respectively. During saline infusion ICP increased within seconds beyond 80 mm Hg and afterward decreased in accordance with the infusion rate. During the infusion of blood, the same initial pressure peak was found, but the ICP remained increased beyond this pressure level throughout the 5-minute infusion period. The HSP70 immunoreactivity in the saline-infused group was found only on Day 1 in the CA1 region and the dentate gyrus, but not in the CA3. After injection of whole blood, there was HSP70-positive staining in the CA1, CA3, and dentate gyrus regions throughout the observation period.

CONCLUSIONS

The controlled cisternal infusion of blood caused neuronal injury that resembled that of previous experimental models that produce SAH by rupture of intracranial vessels with endovascular techniques. Unlike those experiments, the intracisternal infusion technique presented by the authors provides more standardized bleeding with regard to ICP, the volume of subarachnoid blood, and the extent of acute cellular injury.

Lactate and free fatty acids after subarachnoid hemorrhage

The hypothesis that lactate and free fatty acids (FFA) are elevated in the first minutes after subarachnoid hemorrhage (SAH) is tested. Adult rats were subjected to an endovascular SAH through the right internal carotid artery while under anesthesia. The brains were frozen in-situ at 15, 30, 60 min, and 24 h post-hemorrhage. Regional measures of tissue lactic acid and FFA were made in the hippocampi, ipsilateral cortex, contralateral cortex, and cerebellum. Lactic acid levels were significantly elevated from sham animals in each region within the first hour (p<0.0001 cerebellum, right, and contralateral cortex, p<0.01 hippocampus), but did not change significantly over the first hour. At 24 h post-hemorrhage, there was no significant difference in the lactic acid levels from controls. Similarly, total FFA were significantly higher in each region as compared to sham operated controls within the first hour (p<0.001 cerebellum, p<0.05 hippocampus, p<0.05 contralateral cortex, p<0.0001 ipsilateral cortex). By 24 h, there was no significant difference in FFA levels from shams. The data indicate that aerobic metabolism fails and cellular damage with degradation of cell membranes occurs in the first minutes after SAH, and lasts for at least 1 h. However, this process is stabilized within 24 h in our model. Although the largest effect was seen in the ipsilateral cortex, all areas of the brain were effected.

Increase of collagen synthesis and deposition in the arachnoid and the dura following subarachnoid hemorrhage in the rat

Arachnoidal fibrosis following subarachnoid hemorrhage (SAH) has been suggested to play a pathogenic role in the development of late post-hemorrhagic hydrocephalus in humans. The purpose of this study was to investigate the rate of collagen synthesis in the arachnoid and the dura in the rat under normal conditions and to study the time schedule and the localization of the increased collagen synthesis following an experimental SAH. We found that the activity of prolyl 4-hydroxylase, a key enzyme in collagen synthesis, was 3-fold higher in the dura than that in the arachnoid and was similar to the activity in the skin. We then induced SAH in rats by injecting autologous arterial blood into cisterna magna. After SAH, we observed an increase in prolyl 4-hydroxylase activity of the arachnoid and the dura at 1 week. At this time point the enzyme activity in both tissues was 1.7-1.8-fold compared to that in the controls and after this time point the activities declined but remained slightly elevated at least till week 4. The rate of collagen synthesis was measured in vitro by labeling the tissues with [(3)H]proline. The rate increased to be 1.7-fold at 1 to 2 weeks after the SAH in both of the tissues. Immunohistochemically we observed a deposition of type I collagen in the meninges at 3 weeks after the SAH. SAH is followed by a transient increase in the rate of collagen synthesis in the arachnoid and, surprisingly, also the dura. Increased synthesis also resulted in an accumulation of type I collagen in the meningeal tissue, suggesting that the meninges are a potential site for fibrosis. The time schedule of these biochemical and histological events suggest that meningeal fibrosis may be involved in the pathogenesis of late post-hemorrhagic hydrocephalus.

Mitogen-activated protein kinase mediation of hemolysate-induced contraction in rabbit basilar artery

OBJECT

Mitogen-activated protein kinase (MAPK) is an important signaling factor in vascular proliferation and contraction, which are the two features of cerebral vasospasm that follow subarachnoid hemorrhage. The authors studied the possible involvement of MAPK in hemolysate-induced signal transduction and contraction in rabbit basilar artery (BA).

METHODS

Isometric tension was used to record the contractile response of rabbit BA to hemolysate, and Western blots were obtained using antibodies for MAPK. The following results are reported. 1) Hemolysate produced a concentration-dependent contraction of rabbit BA; however, preincubation of arteries with the MAPK kinase (MEK) inhibitor PD-98059 markedly reduced this contraction. The administration of PD-98059 also relaxed, in a concentration-dependent fashion, the sustained contraction induced by 10% hemolysate. 2) The Janus tyrosine kinase 2 inhibitor AG-490, preincubated with arterial rings, reduced the contractile response to hemolysate but failed to relax the sustained contraction induced by this agent. The Src-tyrosine kinase inhibitor damnacanthal and the phosphatidylinositol 3-kinase inhibitor wortmannin failed to reduce hemolysate-induced contraction. 3) Hemolysate produced a time-dependent elevation of MAPK immunoreactivity as seen on Western blots of rabbit BA. The MAPK was enhanced 1 minute after hemolysate exposure and the effect reached maximum levels at 5 minutes. The immunoreactivity of MAPK decayed slowly over time, but the level of this kinase was still higher than the basal level, even at 2 hours after exposure to hemolysate. Preincubation of arteries with the MEK inhibitor PD-98059 abolished the effect of hemolysate on MAPK immunoreactivity.

CONCLUSIONS

Hemolysate produced contraction of rabbit BA, possibly by activation of MAPK, and therefore MAPK inhibitors may be useful in the treatment of cerebral vasospasm.

Subarachnoid hemorrhage in rats: effect of singular or sustained hemodilution with alpha-alpha diaspirin crosslinked hemoglobin on cerebral hypoperfusion

OBJECTIVE

To evaluate the effect of singular or sustained hemodilution, with alpha-alpha diaspirin crosslinked hemoglobin (DCLHb), on the area of hypoperfusion after subarachnoid hemorrhage.

DESIGN

Prospective animal study.

SETTING

Animal research laboratory.

SUBJECTS

Isoflurane anesthetized, mechanically ventilated rats.

INTERVENTIONS

Subarachnoid hemorrhage was induced by injecting 0.3 mL of blood into the cisterna magna. The animals were randomly assigned to one of the following groups (n = 16 in each hemodilution group; eight animals received a single treatment of hemodilution after subarachnoid hemorrhage; and, for eight animals, treatment was sustained for 48 hrs): control group (n = 8), no hematocrit (45%) manipulation; DCLHb group (n = 16), hematocrit decreased to 30% with DCLHb; or Alb group (n = 16), hematocrit decreased to 30% with human serum albumin. After 48 hrs, the area of hypoperfusion (cerebral blood flow < 40 ml/100g/min) was determined with 14C-iodoantipyrine in five coronal brain sections.

MEASUREMENTS AND MAIN RESULTS

For both singular and sustained treatment, the area of hypoperfusion was less in both hemodilution groups than in the control group (p<.05). For four of the five coronal brain sections, no differences were found between the DCLHb and Alb groups within a given hemodilution protocol. In addition, in four of the five coronal brain sections for the DCLHb hemodilution groups and in all five sections for the albumin hemodilution groups, the area of hypoperfusion was less for rats that received sustained hemodilution compared with their respective groups in the singular treatment protocol (p<.05).

CONCLUSIONS

These data support the hypothesis that hemodilution with molecular hemoglobin decreases hypoperfusion after subarachnoid hemorrhage and that sustained hemodilution is more effective than singular treatment. The data do not support the notion that intravascular DCLHb has an adverse effect on cerebral ischemia after subarachnoid hemorrhage.

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.

Posttraumatic cerebral ischemia after fluid percussion brain injury: an autoradiographic and histopathological study in rats

OBJECTIVES

Mild-to-moderate reductions in local cerebral blood flow (ICBF) have been reported to occur in rats after moderate (1.7-2.2 atm) fluid percussion brain injury. The purpose of this study was to determine whether evidence for severe ischemia (i.e., mean ICBF < 0.25 ml/g/min) could be demonstrated after severe brain injury. In addition, patterns of indium-labeled platelet accumulation and histopathological outcome were correlated with the hemodynamic alterations.

METHODS

Sprague-Dawley rats (n = 23), anesthetized with halothane and maintained on a 70:30 mixture of nitrous oxide:oxygen and 0.5% halothane, underwent normothermic (37 degrees C) parasagittal fluid percussion brain injury (2.4-2.6 atm). Indium-111-tropolone-labeled platelets were injected 30 minutes before traumatic brain injury (TBI), while 14C-iodoantipyrine was infused 30 minutes after trauma for ICBF determination. Sham-operated animals (n = 8) underwent similar surgical procedures but were not injured. For histopathological analysis, traumatized rats (n = 5) were perfusion-fixed 3 days after TBI.

RESULTS

In autoradiographic images of indium-labeled platelets, abnormal platelet accumulation that was most pronounced overlying the pial surface was commonly associated with severe reductions in ICBF within underlying cortical regions 30 minutes after TBI. For example, within the lateral parietal cortex, ICBF was significantly reduced from 1.67 +/- 0.11 ml/g per minute (mean +/- standard error of the mean) in sham-operated animals to 0.23 +/- 0.03 ml/g per minute within the traumatized group. In addition to focal severe ischemia, moderate reductions in ICBF were detected throughout the traumatized hemisphere, including the frontal and occipital cortices, hippocampus, thalamus, and striatum. Mild decreases in ICBF were also observed throughout the contralateral cerebral cortex. At 3 days after severe TBI, histopathology demonstrated intracerebral and subarachnoid hemorrhage associated with cerebral contusion and selective neuronal necrosis.

CONCLUSION

These data indicate that multiple cerebrovascular abnormalities, including subarachnoid hemorrhage, focal platelet accumulation, and severe ischemia, are important early events in the pathogenesis of cortical contusion formation after TBI. Injury severity is expected to be a critical factor in determining what therapeutic strategies are attempted in the clinical setting.

Heme oxygenase-1 is induced in glia throughout brain by subarachnoid hemoglobin

The heme oxygenase-1 gene, HO-1, induced by heme, ischemia, and heat shock, metabolizes heme to biliverdin, free iron, and carbon monoxide. Though the distribution of HO-1 has been described in normal rat brain, little is known about how extracellular heme proteins in the subarachnoid space distribute in brain. To address this issue, hemoglobin was injected into the cisterna magna of adult rats. Expression of HO-1 in these animals was compared with saline-injected, BSA-injected, and uninjected controls. Western blot analysis showed that 24 hours after injection oxyhemoglobin increased HO-1 levels approximately four- to fivefold in all brain regions studied compared with saline-injected and BSA-injected controls. In the brain, HO-1 immunoreactivity was evident at 4 hours and peaked at 24 hours after oxyhemoglobin injections, returning to control levels by 4 to 8 days. This HO-1 induction was detected mainly in cells with small, rounded somas bearing two to four truncated processes, a morphology consistent with that of microglia. These cells were double-stained with the microglial marker, OX42, in every brain region examined. It is proposed that subarachnoid hemoglobin may be taken up into microglia wherein heme induces HO-1.

Spasmolytic effect of acidic fibroblast growth factor in early cerebral vasospasm in the rat

BACKGROUND

In animal models of subarachnoid hemorrhage (SAH), basilar artery spasm has been described. Since fibroblast growth factors (FGFs) dilate rat basilar artery in vivo, we tested whether systemic administration of acidic fibroblast growth factor (aFGF) can reverse the basilar artery spasm following rat SAH.

METHODS

SAH was mimicked by injecting autologous blood into the cisterna magna. We used a digital substraction angiography system in order to evaluate the spasmolytic effect of aFGF administered via the axillary artery 7 minutes after the injection of the autologous blood. Control animals received vehicle solution in the same manner.

RESULTS

Intraarterial bolus injection of 2.6 micrograms aFGF, but not the solvent, reverses the acute basilar artery narrowing caused by SAH (23.05% of the baseline value at 5 minutes post-SAH).

CONCLUSIONS

Our results suggest an important role for FGFs in the cerebral tone regulation and support a clinical interest of FGFs in preventing cerebral ischemia following SAH, particularly if these vasoactive effects are added to the known neuroprotective effects of FGFs.

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.

A chronic model to simultaneously measure intracranial pressure, cerebral blood flow, and study the pial microvasculature

In an effort to study changes in cerebral blood flow (CBF), intracranial pressure (ICP) and intracranial compliance (ICC) simultaneously, we have developed a chronic model in rats using a pial window crown with two ports. This model can also be used to study vasoreactivity of pial vessels. Female Sprague-Dawley rats weighing between 225-250 g underwent placement of cranial chamber with dual ports under pentobarbital anesthesia. To test the utility of this technique 45 groups of rats were studied. Group 1 consisted of control animals. Group 2 consisted of rats undergoing 15 min of global cerebral ischemia. Rats in group 3 were evaluated for changes in vessel diameter and ICP after adenosine injection. In group 4 leukocyte/endothelial interactions were evaluated. These groups demonstrate the ability of this model to monitor CBF, ICP, ICC and pial vessel architecture in chronic rat experiments.

Effect of subarachnoid administration of alpha-alpha diaspirin crosslinked hemoglobin on cerebral blood flow in rats

As extravasated red blood cells have been implicated in the pathogenesis of perfusion deficits after subarachnoid hemorrhage, alpha-alpha diaspirin crosslinked hemoglobin (DCLHb) might have a detrimental effect on cerebral perfusion after subarachnoid hemorrhage. We evaluated the effect of subarachnoid administration of DCLHb on cerebral blood flow (CBF). Rats were randomized to receive one of the following solutions into the cisterna magna: Control-0.3 ml of mock cerebrospinal fluid; Blood-0.3 ml of autologous blood; DCLHb-0.3 ml of 10% DCLHb. After 20-min, the area of cerebral hypoperfusion was determined (CBF < 40 ml.100g-1.min-1). The area of hypoperfusion (% area of a coronal brain section, mean +/- SD) was greater in the Blood group (58 +/- 16) than the DCLHb (16 +/- 7) and Control (5 +/- 5) groups (p < 0.05), and was greater in the DCLHb group than the Control group (p < 0.05). These data support a hypothesis that extravasation of blood from the intravascular to the subarachnoid space induces cerebral hypoperfusion. Moreover, the data support the hypothesis that although extravasated molecular hemoglobin decreases CBF, the adverse effect is not as severe as a similar volume of blood.