Cerebrovascular effects of substance P after experimental subarachnoid haemorrhage

The vasoactive effects of substance P (SP), as well as the content of cyclic guanine monophosphate (cGMP), were determined in the rabbit basilar artery after subarachnoid haemorrhage (SAH). Out of 47 rabbits, 24 were subjected to a SAH, induced by injecting 5 ml of autologous arterial blood into the cisterna magna; 23 were used as controls. In 20 animals (10 SAH and 10 controls), isometric tension recording of isolated rings of the basilar artery--dissected 2 days after SAH--was employed to assess the dose-dependent vasodilatation to SP (10(-10) to 10(-6) M) after precontraction with serotonin (10(-8) to 10(-5) M). In 15 animals (8 SAH and 7 controls), the basal cGMP content was measured in the basilar artery 2 days after SAH. In the other 12 animals (6 SAH and 6 controls), the increase in cGMP content was measured in the basilar artery after a 10-minute incubation with SP (10(-6) M). SP caused significantly less dilatation in animals subjected to SAH than in controls, especially for concentrations between 10(-9) and 10(-6) M (p < 0.001). The cGMP content in the arteries 2 days after SAH was significantly lower than in control arteries (31.5 +/- 7.3 against 57.3 +/- 4.3 pmoles/g tissue). In the preparations incubated with SP, the increase of cGMP was 440 +/- 115% in the control arteries, and only 97 +/- 30% in the arteries after SAH. It is concluded that the vasodilator activity of SP is significantly impaired after SAH.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of intracisternal and intravenous calcitonin gene-related peptide on experimental cerebral vasospasm in rabbits

We investigated the vasodilatory effect of intracisternal (i.c.) and intravenous (i.v.) administration of calcitonin gene-related peptide (CGRP) on arterial narrowing after experimental subarachnoid hemorrhage (SAH). Forty-one rabbits were divided into five groups: control (normal animals); SAH plus i.c. infusion of vehicle; SAH plus i.c. infusion of CGRP; SAH plus i.v. infusion of vehicle; SAH plus i.v. infusion of CGRP. In all but the control group, either CGRP (100 ng/kg/min) or vehicle solution was infused for two hours immediately prior to sacrifice by perfusion-fixation. A morphometric technique was employed to measure the luminal diameter of rabbit basilar arteries two days after SAH. The diameter of the basilar arteries in either the i.c. or i.v. CGRP groups was significantly greater than that of the respective vehicle group (i.c., p < 0.001; i.v., p < 0.01). Although there was no significant difference in systemic arterial blood pressure after infusion between the i.c. vehicle and i.c. CGRP groups, i.v. CGRP caused significant hypotension. Our results suggest that exogenous CGRP has some therapeutic potential for arterial narrowing after SAH not only by intrathecal application, but also by systemic use.

The International Cooperative Study on the Timing of Aneurysm Surgery. The North American experience

BACKGROUND AND PURPOSE

The timing of aneurysm surgery after subarachnoid hemorrhage is a major neurosurgical controversy addressed by the International Cooperative Study on the Timing of Aneurysm Surgery (1980-1983). The present report examines the results of this trial in the subgroup of patients admitted to North American centers.

METHODS

The method of study was a large, multicenter, prospective, epidemiological survey. Neurosurgeons were required to indicate prospectively the interval to planned aneurysm surgery at the time of patient admission. Outcome at 6 months was determined by a blinded evaluator, and overall management results were analyzed by the planned surgical interval.

RESULTS

Seven hundred seventy-two (21.9% of the total study population) patients admitted from days 0 to 3 after subarachnoid hemorrhage were accrued in North American centers. Overall outcome in patients planned for surgery in days 0-3 was equivalent in terms of mortality (after adjustment for prognostic variables) to patients planned for days 11-32, but the early patients had significantly improved rates of good recovery (70.9% versus 61.7%, p less than 0.01). Patients planned for surgery during the days 7-10 interval had nearly twice the mortality of patients in the other intervals.

CONCLUSIONS

In contrast to the results from the overall trial, which found no difference between early and delayed surgery, results were best in North American centers when surgery was planned between days 0 and 3 after subarachnoid hemorrhage. These findings argue strongly for early diagnosis and referral for surgical intervention of North American patients suspected of having a ruptured cerebral aneurysm.

Effect of bilirubin on rabbit cerebral arteries in vivo and in vitro

The effect of bilirubin on vasoreactivity was examined in the exposed rabbit basilar artery (diameter, 1045 +/- 17 microns; n = 18) and its cortical branches (diameter, 265 +/- 11 microns; n = 43) in vivo. Vasoconstriction induced by uridine triphosphate (UTP; 10(-5) to 10(-3) mol/L) was observed in vivo before and after a 60-minute application of supersaturated bilirubin (10(-4) mol/L). Bilirubin was dissolved in modified artificial cerebrospinal fluid (pH 7.4) or in physiological salt solution (pH 7.6). The latter was spectrophotometrically estimated to contain a higher concentration of free bilirubin because of the formation of less colloid. After treatment with bilirubin in artificial cerebrospinal fluid, the effect was minimal in the basilar arteries (n = 7), whereas the diameter of the branches was reduced by 9.6 +/- 1.5% (n = 23) and UTP-induced vasoconstriction was potentiated. After application of bilirubin in physiological salt solution, the basilar arteries contracted slightly (-2.1 +/- 0.9%; n = 6) and the UTP-induced vasoconstriction in the branches was attenuated (n = 12). After a 60-minute incubation of basilar artery with bilirubin in physiological salt solution in vitro, isometric tension recordings showed a diminution in KCl- and UTP-induced vasoconstrictions. Acetylcholine- and sodium nitroprusside-induced relaxations were also attenuated. It is suggested that bilirubin may exert different effects depending on the size of arteries and the concentration of free bilirubin. The constrictor and potentiating effects of bilirubin could be caused by the impairment of the relaxation mechanism. When the toxic effect of bilirubin becomes severe, the constrictor mechanism is also damaged.

Biphasic constriction of rabbit basilar artery following experimental subarachnoid hemorrhage: a morphometric study

To assess the changes in arterial structure resulting from subarachnoid hemorrhage, morphometric analysis was performed on basilar arteries from rabbits that had received an experimental subarachnoid hemorrhage up to 6 days earlier. For morphometric determination, the cross-sectional area of the media, the area of the lumen, and the length of the internal elastic lamina were measured planimetrically. The morphometric diameter of the lumen, the media-to-radius ratio, and several other morphometric parameters were also calculated. Subarachnoid hemorrhage induced significant biphasic constriction of the basilar artery without any changes in the cross-sectional area of the media. The relative amount of smooth muscle cell decreased significantly in the late stage of hemorrhage.

Does vasospasm occur in small pial arteries and arterioles of rabbits?

BACKGROUND

Vasospasm is a serious complication associated with subarachnoid hemorrhage. Successful management of vasospasm will ultimately depend on a clear understanding of the scope of this phenomenon, including whether arterial elements of different calibers are equally affected. We therefore examined the responses to subarachnoid hemorrhage in rabbit basilar arteries, small pial arteries, and arterioles.

SUMMARY OF REPORT

We compared the brain stem pial arteries of 10 perfusion-fixed male New Zealand White rabbits after experimental subarachnoid hemorrhage to those of five control rabbits using morphological analysis of cross-sections of plastic-embedded vessels. After subarachnoid hemorrhage, the internal elastic lamina was highly corrugated in all basilar arteries (mean diameter 319 +/- 51 microns). These arteries were severely constricted in comparison with the control group, in which the mean diameter was 691 +/- 17 microns, and corrugation of the internal elastic lamina was not present. In contrast, small pial arteries and arterioles very rarely demonstrated a vasoconstrictive configuration after subarachnoid hemorrhage. The contractility of the smaller vessels was confirmed by injecting 2 mg/kg BaCl2 intracisternally. Following BaCl2 injection, corrugation of the internal elastic lamina was detected in the small arteries and arterioles as well as the basilar arteries.

CONCLUSIONS

We conclude that experimental chronic vasospasm after subarachnoid hemorrhage in rabbits tends to occur in large conducting arteries rather than in smaller pial arteries and arterioles.

Intracisternal recombinant tissue plasminogen activator after aneurysmal subarachnoid hemorrhage

Fifteen patients undergoing surgery within 48 hours of aneurysm rupture were administered recombinant tissue plasminogen activator (rt-PA) directly into the basal subarachnoid cisterns after minimal surgical clot removal and aneurysm clipping. Preoperatively, 13 patients had diffuse or localized thick subarachnoid blood clots on computerized tomography (CT), and two had diffuse thin clots. The rt-PA was given as a single intraoperative injection of 7.5 mg (one patient), 10 mg (nine patients), or 15 mg (five patients). Postoperative cisternal drainage was employed in three patients. All patients except one demonstrated partial to complete cisternal clot clearance on CT scans within 24 hours after surgery. The patient who showed no clot reduction was the only patient in this series to develop symptomatic vasospasm and was the only fatality, dying 8 days after rupture. No vasospasm was seen on follow-up cerebral angiography in six of the 14 responding patients, and mild-to-moderate arterial narrowing was seen in at least one major cerebral artery in the remaining eight patients. Severe angiographic vasospasm was not seen, although the patient who died did not undergo repeat angiography. There was one major complication early in the series which seemed clearly related to treatment, and that was a large extradural hematoma occurring within several hours of craniotomy. Intrathecal fibrinolytic treatment appears effective in clearing subarachnoid clot and reducing vasospasm, and may be associated with acceptable risks if given to patients with large-volume subarachnoid hemorrhages at high risk for severe vasospasm.

The effect of nicardipine on vasospasm in rabbit basilar artery after subarachnoid hemorrhage

This study was performed to examine the effect of the dihydropyridine calcium antagonist, nicardipine, on vasospasm after experimental subarachnoid hemorrhage (SAH) in the rabbit. The study was carried out in two parts: 1) effect of intravenous nicardipine (n = 45) and 2) effect of intracisternal nicardipine (n = 21). SAH was induced by injecting 5 ml of autologous arterial blood into the cisterna magna. In the intravenous study, there were five groups: 1) SAH without treatment; 2) SAH with vehicle (saline); 3) SAH and intravenous infusion of low-dose nicardipine (0.01 mg/kg/h); 4) SAH and intravenous infusion of high-dose nicardipine (0.15 mg/kg/h); and 5) controls without SAH. The intravenous infusions were started immediately after SAH and continued for 48 hours until death. In the intracisternal study, there were three groups: 1) SAH without treatment; 2) SAH with intracisternal administration of nicardipine (0.37 mg/h); and 3) controls without SAH. Intracisternal infusions were begun 70 hours after SAH and continued for 2 hours until death. After perfusion-fixation, the basilar artery was removed and processed for morphometric analysis. In the intravenous study, vessels from animals subjected to SAH were significantly narrowed when compared with controls, although after high-dose nicardipine vessel caliber was slightly larger than in the other SAH groups. Animals given intracisternal nicardipine showed a nonsignificant reduction of caliber as compared with controls: only 12% decrease in diameter and 22% decrease in luminal area. In the rabbit SAH model, nicardipine had a very modest effect on vasospasm at the doses tested.

Mechanism of enlargement of major cerebral collateral arteries in rabbits

Major cerebral collateral arteries enlarge following bilateral ligation of the common and internal carotid arteries. The purpose of this investigation was to determine the relative contribution of cellular hypertrophy versus cellular hyperplasia to this vessel change in a morphometric analysis as well as the functional properties of remodeled vessels in an in vitro study. We assessed cell number and vessel dimensions by morphometric analysis of 16 perfusion-fixed rabbit basilar arteries. Results demonstrated significant increases in luminal diameter from 761 to 946 microns (p less than 0.01), medial cross-sectional area from 5.1 x 10(4) to 7.6 x 10(4) micron2 (p less than 0.005), smooth muscle cell volume from 9.19 x 10(5) to 1.44 x 10(6) micron3 (p less than 0.0005), and overall arterial length from 17.41 to 20.36 mm (p less than 0.005) in basilar arteries from the eight ligated rabbits compared with the eight sham-operated controls. Smooth muscle cell volume fraction and cell numerical density were unchanged whereas the number of cells per unit length of artery was increased significantly from 21.5 to 31.0 cells/micron (p less than 0.05). These data indicate that smooth muscle cell hyperplasia rather than hypertrophy contributes to increases in vessel mass. Functional properties of the basilar arteries from 10 ligated and 10 normal control rabbits were analyzed in vitro. Results showed increased contraction to potassium chloride (approximately 74%) (p less than 0.01) and increased sensitivity of smooth muscle to acetylcholine (p less than 0.05) while maximal relaxation was the same as control in the ligated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of subarachnoid hemorrhage on serotonin uptake and metabolism in rabbit basilar artery

The effects of subarachnoid hemorrhage (SAH) on neuronal uptake and metabolism of serotonin (5-HT) in the rabbit basilar artery were examined. Extracted 3H-amines from the isolated arteries after incubation with [3H]5-HT were separated by column chromatography. Radioactivity of 5-HT and 5-hydroxyindoleacetic acid was, respectively, 52.7 +/- 13.9 and 22.9 +/- 5.4 x 10(2) dpm/mg tissue in the control group (n = 8); 32 and 18% of control after denervation (n = 6); 99 and 12% of control after treatment with pargyline (n = 7); and 65 and 76% of control after SAH (n = 7). These results suggest that the neuronal uptake of 5-HT is impaired by SAH, although monoamine oxidase activity is relatively preserved.

Effect of subarachnoid hemorrhage on serotonin uptake and release in the rabbit basilar artery

This study analyzes the changes induced by subarachnoid hemorrhage (SAH) on the serotonin (5-hydroxytryptamine, 5-HT) uptake and release evoked in rabbit basilar arteries by tyramine. Rabbits were injected with 5 ml of autologous arterial blood into the cisterna magna to produce SAH. Tritium accumulation in basilar arteries was measured after 30 minutes of incubation with 10(-7) M [3H]5-HT and a subsequent 120-minute superfusion (1 ml/min) period. The uptake of 5-HT by arteries 1, 2, 3, and 7 days after SAH was found to be 109%, 69%, 57% (P less than 0.05), and 67% (P less than 0.05) (n = 4, 4, 9, and 6; P less than 0.05) of control (n = 13; 16.8 +/- 1.2 X 10(2) dpm/mg tissue), respectively. The neuronal (cocaine-sensitive) uptake of 5-HT in the arteries 3 days after SAH decreased to approximately 38% of control, whereas the extraneuronal (cocaine-insensitive) uptake of both groups had almost the same absolute value (n = 6 and 6; 4.4 +/- 0.4 and 4.8 +/- 0.4 X 10(2) dpm/mg). Autoradiographic study disclosed that dense clusters of silver grains in the adventitia were not observed after treatment with cocaine (3 X 10(-5) M), although a diffuse distribution of grains was present throughout the vascular wall. The labeled arteries were stimulated by superfusion of tyramine, which is known to replace amines in the sympathetic nerve ending. Tyramine (10(-6) and 10(-4) M)-induced 3H efflux was significantly potentiated by SAH (n = 6) and was suppressed by treatment with cocaine.(ABSTRACT TRUNCATED AT 250 WORDS)

A Study of the Effectiveness of the Iron-Chelating Agent Deferoxamine as Vasospasm Prophylaxis in a Rabbit Model of Subarachnoid Hemorrhage

The pathogenesis of cerebral vasospasm occurring after subarachnoid hemorrhage (SAH) is unknown. Several lines of experimentation have suggested a free radical mechanism in the etiology of vasospasm. Iron is an important catalyst in the generation of free radicals and lipid peroxides in response to tissue injury. We hypothesize that the elaboration of iron from the subarachnoid clot might result in enhanced generation of free radicals and lipid peroxidation. If so. then treatment with deferoxamine, an iron-chelating compound, might reduce the formation of free radicals and thereby ameliorate vasospasm. This hypothesis was examined in a rabbit model of experimental cerebral vasospasm. New Zealand White rabbits were divided into the following experimental groups: control (normal) animals (n = 7), control animals treated with deferoxamine (n = 3), animals subjected to SAH and killed on Day 2 (n = 7), animals subjected to SAH on Day 2 and treated with deferoxamine (n = 9), animals subjected to SAH killed on Day 3 (n = 7). and animals subjected to SAH on Day 3 and treated with deferoxamine (n = 7). Deferoxamine treatment (50 mg/kg/8 hours) was begun 16 hours before the induction of SAH and continued until the animals were killed by perfusion fixation. The basilar artery caliber was assessed using morphometric techniques. The diameter of the basilar arteries in the control animals was 0.64 ± 0.02 mm. Deferoxamine treatment alone did not alter the artery diameter. SAH resulted in a decrease in basilar artery diameter by 20% on Day 2 and 27% on Day 3. Deferoxamine treatment attenuated the SAH-induced spasm minimally on Day 2 but significantly on Day 3 (Day 3 diameter = 0.60 ± 0.04; P &lt; 0.015). These preliminary results show promise for deferoxamine therapy in the treatment of vasospasm occurring after SAH. These data support the notion that SAH-induced vasospasm is mediated by iron, possibly via the generation of free radicals.

Pharmacological reversibility of experimental cerebral vasospasm

Using a morphometric technique, the pharmacological reversibility of luminal narrowing after experimental subarachnoid hemorrhage (SAH) was investigated. For vasodilation, a "cocktail" consisting of 10(-4) M papaverine, 2 x 10(-4) M sodium nitroprusside, and 10(-5) M adenosine was administered intra-arterially. Forty-two rabbits were divided into six groups: control (normal animals); control plus cocktail (normal animals perfused with the cocktail before fixation); SAH (animals sacrificed 48 hours subsequent to intracisternal injection of 1.5 ml/kg of arterial blood); SAH plus cocktail (SAH plus perfusion with the cocktail); BaCl2 (animals sacrificed 10 minutes after intracisternal injection of 2 ml of 3 x 10(-3) M BaCl2); and BaCl2 plus cocktail (BaCl2 animals perfused with the cocktail). The diameter of the basilar arteries in the control and the control plus cocktail groups was not significantly different. BaCl2 reduced the diameter 44% and SAH reduced the diameter 27%. There were no significant differences between the diameter of the BaCl2 plus cocktail group and SAH plus cocktail group when compared with the control or the control plus cocktail group. Morphological examination by light and transmission electron microscopy showed luminal narrowing and corrugation of the elastic lamina with few degenerative or proliferative changes of the vessel wall in animals with SAH. These results suggest that cerebral vasospasm is caused initially by smooth muscle contraction rather than by proliferative vasculopathy and that it is not an irreversible process.

Pharmacological Reversibility of Experimental Cerebral Vasospasm

Using a morphometric technique, the pharmacological reversibility of luminal narrowing after experimental subarachnoid hemorrhage (SAH) was investigated. For vasodilation, a “cocktail” consisting of 10−4 M papaverine, 2 × 10−4 M sodium nitroprusside, and 10−5 M adenosine was administered intra-arterially. Forty-two rabbits were divided into six groups: control (normal animals); control plus cocktail (normal animals perfused with the cocktail before fixation); SAH (animals sacrificed 48 hours subsequent to intracisternal injection of 1.5 ml/kg of arterial blood); SAH plus cocktail (SAH plus perfusion with the cocktail); BaCl2 (animals sacrificed 10 minutes after intracisternal injection of 2 ml of 3 × 10−3 M BaCl2); and BaCl2 plus cocktail (BaCl2 animals perfused with the cocktail). The diameter of the basilar arteries in the control and the control plus cocktail groups was not significantly different. BaCl2 reduced the diameter 44% and SAH reduced the diameter 27%. There were no significant differences between the diameter of the BaCl2 plus cocktail group and SAH plus cocktail group when compared with the control or the control plus cocktail group. Morphological examination by light and transmission electron microscopy showed luminal narrowing and corrugation of the elastic lamina with few degenerative or proliferative changes of the vessel wall in animals with SAH. These results suggest that cerebral vasospasm is caused initially by smooth muscle contraction rather than by proliferative vasculopathy and that it is not an irreversible process.

Impaired capillary perfusion and brain edema following experimental subarachnoid hemorrhage: a morphometric study

To evaluate microcirculatory disturbance and cerebral edema associated with subarachnoid hemorrhage (SAH), both stereological morphometry on the intraparenchymal capillary network and microgravimetry were performed on a rabbit SAH model. Autologous arterial blood (5 ml) was injected into the cisterna magna, and the animals were sacrificed at intervals of 6 hours, 1 day, 2 days, or 6 days after SAH. Capillaries in the piriform cortex, parasagittal cortex, and ventral brain stem of the midline-hemisectioned brain were injected with Evans blue dye 1 minute before sacrifice, and were planimetrically evaluated under a fluorescence microscope connected to an image analysis system. Stereological and morphological parameters including the volume density, surface density, numerical density, minimum intercapillary distance, and the diameter of Evans blue-perfused capillaries were also computed. In the piriform cortex and ventral brain stem, the volume and surface densities were significantly reduced and the minimum intercapillary distance was significantly increased 1 to 2 days after SAH. In the parasagittal cortex far from the cisternal clot, changes in the parameters were minimal. Cerebral blood volume (CBV) in the normal condition and edema formation associated with SAH were studied by the microgravimetric technique. The mean CBV in the parasagittal cortex, piriform cortex, and brain stem was 6.9%, 6.8%, and 5.6%, respectively. Following SAH, specific gravity in the piriform cortex and the ventral brain stem of the other side of the hemisectioned brain was significantly decreased at 1 to 2 days, showing a change parallel to that of the stereological parameters. The results obtained from the morphometric technique indicated the occurrence of impaired capillary perfusion and reduced capillary blood volume following SAH, while microgravimetry suggested the formation of brain edema during this period. These changes in the intraparenchymal vessels may play an important role in the pathophysiology of SAH.

The International Cooperative Study on the Timing of Aneurysm Surgery. Part 2: Surgical results

A prospective, observational clinical trial was conducted by the International Cooperative Study on the Timing of Aneurysm Surgery to determine the best time in relation to the hemorrhage for surgical treatment of ruptured intracranial aneurysms. Sixty-eight centers contributed 3521 patients in a 2 1/2-year period beginning in December, 1980. Analysis by a prespecified "planned" surgery interval demonstrated that there was no difference in early (0 to 3 days after the bleed) or late surgery (11 to 14 days). Outcome was worse if surgery was performed in the 7 to 10-day post-bleed interval. Surgical results were better for patients operated on after 10 days. Patients alert on admission fared best; however, alert patients had a mortality rate of 10% to 12% when undergoing surgery prior to Day 11 compared with 3% to 5% when surgery was performed after Day 10. Patients drowsy on admission had a 21% to 25% mortality rate when operated on up to Day 11 and 7% to 10% with surgery thereafter. Overall, early surgery was neither more hazardous nor beneficial than delayed surgery. The postoperative risk following early surgery is equivalent to the risk of rebleeding and vasospasm in patients waiting for delayed surgery.

Etiology of the disruption in blood-arterial wall barrier following experimental subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage is associated with a sudden rise in intracranial pressure, acute arterial hypertension, and subarachnoid blood. The role that each of these factors may play in the development of the acute barrier disruption of the major cerebral arteries following subarachnoid hemorrhage was investigated in 42 rabbits. Horseradish peroxidase was given intravenously to assess the integrity of the barrier by transmission electron microscopy. Permeation of the tracer into the vessel was noted only in animals with increased intracranial pressure. A sudden rise in intracranial pressure is suggested to trigger acute barrier disruption following subarachnoid hemorrhage.

Blood-brain barrier disturbance following subarachnoid hemorrhage in rabbits

We studied disruption of the blood-brain barrier after experimental subarachnoid hemorrhage induced by an injection of 4 ml autologous arterial blood into the cisterna magna of rabbits. The animals were killed at 40 minutes, 6 hours, 1 day, 2 days, 4 days, or 6 days after subarachnoid hemorrhage. We assessed the integrity of the barrier function of intraparenchymal vessels in the ventral brain stem and cerebral hemispheres morphologically with transmission electron microscopy, using horseradish peroxidase as a tracer. In the ventral brain stem, which was in direct contact with the cisternal clots, markedly increased peroxidase staining toward the core of the brain stem was observed on the first day after subarachnoid hemorrhage. In an area of the cerebral hemispheres distant from the clots, barrier disturbance was prominent in the 6-hour specimens, and permeation of the tracer was spotty. From the distribution and morphological findings of these lesions, permeability changes in the ventral brain stem may have been caused by a direct effect of the cisternal clots; in the cerebral hemispheres, hemodynamic factors and changes in intracranial pressure associated with the elderly stages of subarachnoid hemorrhage seemed to be responsible. These results suggest that barrier disturbance associated with subarachnoid hemorrhage may be multifactorial in time course and location.

The International Cooperative Study on the Timing of Aneurysm Surgery. Part 1: Overall management results

The International Cooperative Study on the Timing of Aneurysm Surgery evaluated the results of surgical and medical management in 3521 patients between December, 1980, and July, 1983. At admission, 75% of patients were in good neurological condition and surgery was performed in 83%. At the 6-month evaluation, 26% of the patients had died and 58% exhibited a complete recovery. Vasospasm and rebleeding were the leading causes of morbidity and mortality in addition to the initial bleed. Predictors for mortality included the patient's decreased level of consciousness and increased age, thickness of the subarachnoid hemorrhage clot on computerized tomography, elevated blood pressure, preexisting medical illnesses, and basilar aneurysms. The results presented here document the status of management in the 1980's.

Treatment of right hemispheric cerebral infarction by hemicraniectomy

An anecdotal series of nine patients (three men and six women with an average age of 57 years) presented with progressive neurologic deterioration while on medical therapy for large right hemispheric cerebral infarction. Clinical signs of uncal herniation (anisocoria or fixed and dilated pupils, and/or left hemiplegia with right decerebrate posturing) were present in seven of these nine patients. Computerized tomography of the head confirmed mass effect from cerebral edema. It was the clinical judgment of the treating neurologists and neurosurgeons that each of these nine patients would perish unless surgical decompression of the infarcted brain was performed. Accordingly, each was treated with right hemicraniectomy and dural augmentation. Six patients demonstrated neurologic improvement on the first postoperative day. One patient, with a postoperative diagnosis of lung cancer, died 1 month after surgery. The remaining eight patients are currently living with their families with a follow-up period ranging from 5 to 25 months. Patient outcome as evaluated by the Barthel Index indicates that three individuals are functioning with minimal assistance and that the remaining six patients are functionally dependent. After rehabilitative therapy, four patients returned for elective cranioplasty. These results suggest that hemicraniectomy can be an effective lifesaving procedure for malignant cerebral edema after large hemispheric infarction.

The timing of surgery and vasospasm

The relationship of time of surgery and vasospasm is influenced by three factors: (1) the time course of vasospasm, (2) the effectiveness of clot removal at surgery, and (3) the choice of medical management to prevent rebleeding and to treat vasospasm. Data to date demonstrate that angiographic vasospasm and vasospasm-related deficits occur in the period from 4 to 14 days after subarachnoid hemorrhage. Surgical intervention in the period of risk for vasospasm is associated with higher morbidity and mortality rates. Morbidity and mortality rates are lowest following surgery in patients who have delayed surgery; however, morbidity and mortality rates for overall management are equivalent for patients with early surgery because of vasospasm and rebleeding in patients waiting for delayed surgery. The surgical removal of the clot may be accomplished in only a limited number of patients, and most series do not reflect a large change in vasospasm occurrence following early surgery. Changes to more aggressive medical therapy in terms of prevention or reversal of ischemia from vasospasm rendered after the aneurysm is clipped and rebleeding is prevented have been initiated during the past decade. The effectiveness and safety of these treatments may play an important future role in the choice of time of surgery and the relationship of time of surgery to vasospasm-related deficits.

Antifibrinolytic therapy and cerebral vasospasm

The role of antifibrinolytic drugs in the management of patients with aneurysmal subarachnoid hemorrhage continues to remain uncertain. Recent controlled studies suggest that although these agents may alter the course of the illness, they confer no benefit in terms of overall outcome. Confronted with these data, clinicians in North America have radically altered their management of patients with ruptured aneurysms in the last decade. In the Timing of Surgery Study (1980-1983), 54% of patients were treated with antifibrinolytic drugs and only 32% underwent surgical clipping of the aneurysm on days 0-3 from the subarachnoid hemorrhage. In contrast, only 13% of the patients in the Randomized Trial of Nicardipine in Subarachnoid Hemorrhage (1987-1989) received antifibrinolytics, whereas 53% had early surgery (unpublished observations). Further study will be required to determine if this strategy has resulted in an improvement in overall outcome. Some observers have suggested that as effective therapy for symptomatic vasospasm evolves (e.g., with hypertensive or hypervolemic therapy or calcium antagonists), the adverse effects of antifibrinolytic drugs on brain ischemia may be ameliorated. This idea must be confirmed by further evaluation of the combined use of these treatments. In the interim, antifibrinolytic drugs, if used at all, should be used with caution, and their use should be restricted to those patients judged not to be candidates for early surgery. If therapy cannot be started before day 7 after subarachnoid hemorrhage, it should not be started at all, as the reduced rate of rebleeding after the first 7 days does not justify the increased risk of brain ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of endothelium in cerebral vasospasm

Following subarachnoid hemorrhage, the smooth muscle cells of the major cerebral arteries are exposed to a variety of vasoconstrictor substances, including those liberated from subarachnoid clots in the plasma, released from activated platelets adherent to the damaged endothelium, and released from the injured endothelium. There is no doubt that these vasoconstrictor substances induce the long-lasting contraction of the cerebral arteries. In this article, we discussed supplement mechanisms associated with endothelial damage in the major cerebral arteries with regard to the pathogenesis of vasospasm. Increased permeability in the major cerebral arteries after subarachnoid hemorrhage may allow access of vasoconstrictor and mitogenic substances to the media. These substances may augment the contraction of smooth muscle cells, produce the subendothelial thickening, or both. In addition, the impairment of vasodilatory properties in the major cerebral arteries, including the diminished synthesis of PGI2 and EDRF, as well as the inhibition of EDRF and neurogenic vasodilation by hemoglobin, probably augment the contraction triggered by a variety of vasoconstrictor substances. Furthermore, the impairment of antithrombogenic properties after subarachnoid hemorrhage could participate in the disturbance of cerebral microcirculation and the development of cerebral ischemic symptoms.

Isolation and characterization of endothelial cells from bovine cerebral arteries

For our laboratory's investigation into the role of the endothelial cells in vasospasm following subarachnoid hemorrhage and in inflammatory diseases, we found it necessary to devise a modified method of cell culture, which would be appropriate for studying human endothelial cells from lobectomized brain. We report our techniques to increase cell harvest and ensure reproducibility, our method of culturing endothelial cells from bovine major cerebral arteries, and our morphologic and immunocytochemical characterization of these cells. To increase the harvest of endothelial cells, the blood cells were washed from the lumen of the major cerebral arteries at the slaughterhouse and a modified reversed vessel technique was employed. The monolayer of cultured endothelial cells displayed a cobblestone appearance when it reached confluency and transmission electron microscopy revealed junctional complexes and interdigitation of cytoplasm at Passages 10 and 17. The cells stained positively for Factor VIII-related antigen at Passages 3, 5, 7, 10, and 15. Also the cells metabolized acetylated low-density lipoprotein at Passage 8. To determine the purify of the cultured endothelial cells, an immunocytochemical study of the cytoskeleton was performed on Passage 5 cells using either rhodamine-phalloidin or antibodies against smooth muscle myosin, desmin, and vimentin.

Decreases in excitatory synaptic transmission and increases in recurrent inhibition in the rat dentate gyrus after transient cerebral ischemia

Excitatory transmission along the perforant path from the entorhinal cortex to the granule cells of the dentate gyrus was evaluated two days after 10 min of transient cerebral ischemia in the rat. The amplitude of the population spike, and the amplitude and the initial slope of the population excitatory postsynaptic potential (EPSP) evoked by the perforant path stimulation were measured across a range of stimulus intensities, and were compared with control values. Inhibitory interactions were evaluated using the paradigm of paired pulse stimulation, comparing the amplitude of the population spike evoked by the second pulse of a pair to the initial spike. The maximal values of the initial slope of the population EPSP and the population spike were reduced in the ischemic group. Also, the extent of paired pulse inhibition was greater in the ischemic group. These results suggest that: (1) excitatory synaptic transmission along the perforant path is impaired in the postischemic period, (2) inhibition of the dentate granule cells is enhanced in this period. These results are not consistent with the hypothesis that there is a hyperactivation of the tri-synaptic circuit in the chronic postischemic period that accounts for the excitotoxic death of CA1 neurons.

Muscarinic cholinergic receptors on the endothelium of human cerebral arteries

To characterize the muscarinic cholinergic receptors on the endothelium of human cerebral arteries, isometric tension measurement and receptor autoradiographic studies were performed. Acetylcholine (ACh) induced dose-dependent relaxation of human cerebral arteries precontracted by 10(-5) M serotonin, with an EC50 of 1.9 +/- 0.6 X 10(-6) M (n = 7). The relaxation was abolished by 10(-5) M hemoglobin. Autoradiography, using the muscarinic antagonist [3H]propylbenzilycholine mustard, demonstrated the high density of muscarinic cholinergic receptors on the endothelial cells of human cerebral arteries, especially on the luminal surface of the endothelium. These findings suggest that ACh-induced relaxation mediated by muscarinic cholinergic receptors on the endothelium has a physiological function in human cerebral arteries.

Effects of subarachnoid hemorrhage on platelet-derived vasoconstriction of rabbit basilar artery

The effects of subarachnoid hemorrhage on platelet-derived vasoconstriction of the isolated rabbit basilar artery were examined using an isometric tension recording method. The subarachnoid hemorrhage was induced by injecting arterial blood in the cisterna magna. The following points were confirmed: (1) the maximal contraction produced by the platelets (10(7)/mL) treated with indomethacin or dazoxiben (thromboxane synthetase inhibitor) were suppressed (65% or 70% of the control); (2) the contraction of the arteries treated with ONO-3708 (thromboxane A2 antagonist) or ketanserin was inhibited (73% or 8.4%), as was contraction after subarachnoid hemorrhage (67% or 14%); (3) platelet-induced contraction was potentiated after subarachnoid hemorrhage; and (4) serotonin-induced contraction was potentiated after subarachnoid hemorrhage. However, synthetic thromboxane A2-induced contraction was not potentiated. The present experiments suggest that both serotonin and thromboxane A2 contribute to vasoconstrictions induced by the platelets, before and after subarachnoid hemorrhage. The platelet-derived contraction response is potentiated after subarachnoid hemorrhage and serotonin is responsible for the increased reactivity.

Neurologic assessment of subarachnoid hemorrhage in a large patient series

Data from the International Cooperative Aneurysm Study including 3521 cases of aneurysmal subarachnoid hemorrhage were used to statistically derive a simple scoring method for assessing neurologic status of subarachnoid hemorrhage patients. Discriminant analysis was used to identify the best combination and weighting of seven neurologic assessment variables to classify outcomes at 6 months post-subarachnoid hemorrhage. The sum of eye opening response and worst motor response classified patient outcomes nearly as well as all variables combined. The validity of this summary score was tested using good recovery and mortality endpoints. The result is a useful scale for classifying subarachnoid hemorrhage patients.

Sensitivity and specificity of transcranial Doppler ultrasonography in the diagnosis of vasospasm following subarachnoid hemorrhage

Vasospasm is the leading cause of death and disability in patients with aneurysmal subarachnoid hemorrhage (SAH). Transcranial Doppler ultrasonography (TCD) can detect the arterial narrowing noninvasively, but the sensitivity and specificity of this technique have not been reported in a population of patients with a high frequency of angiographic vasospasm. In this study, 34 consecutive patients with SAH undergoing angiography during the period of risk for vasospasm had technically adequate TCD examinations within 24 hours of the angiogram. Using a mean flow velocity of 120 cm/sec and above as indicative of vasospasm, TCD correctly detected angiographic vasospasm in 17 patients; there were no false positives. It correctly determined that 5 patients did not have vasospasm, whereas there were 12 false negatives. False negatives were frequently due to angiographic vasospasm involving vessels not assessable by TCD. The correlation between mean flow velocity and the angiographic residual lumen diameter of the middle cerebral artery was statistically significant. These data suggest that TCD is a highly specific (100%), but less sensitive (58.6%) test for the detection of angiographic vasospasm following SAH. Confirmatory angiography may be avoided if the TCD study is positive, but additional studies may be necessary if the clinical picture is suspicious and the TCD study is negative.

Time course of the blood-arterial wall barrier disruption following experimental subarachnoid haemorrhage

The time course of the blood-arterial wall barrier disruption following experimental subarachnoid haemorrhage (SAH) was studied in 24 rabbits. Animals with SAH received two successive blood injections through the cisterna magna. Horseradish peroxidase (HRP) was given intravenously 30 minutes before sacrifice to assess the integrity of the barrier. In the basilar arteries taken from animals that were sacrificed 4 days after the first SAH, HRP-reaction products were diffusely observed in the subendothelial space. Three weeks following the first SAH, permeation of HRP was still observed in half of the animals. However, in animals sacrificed 7 weeks after the first SAH, no permeation of HRP into the subendothelial space was noted. Opening of the interendothelial space seemed to be the major mechanism for HRP permeation into the subendothelial space rather than transendothelial vesicular transport. Disruption of the blood-arterial wall barrier in the major cerebral arteries following SAH may play a role in the pathogenesis of vasospasm.

The distribution of intravenous nicardipine in rat brain after subarachnoid hemorrhage

The distribution of intravenously injected nicardipine in rat brain was investigated, as well as the influence of subarachnoid hemorrhage on its distribution. Autoradiographic studies demonstrated the accumulation of 3H-nicardipine only in the ventricles and subarachnoid spaces around pial vessels in normal brains. Thirty minutes after subarachnoid hemorrhage, the concentration of 3H-nicardipine was higher in the ventricles and in the subarachnoid space than that found in normal brains. It is concluded that nicardipine penetrates into the subarachnoid spaces and ventricles from pial vessels and/or choroid plexus, and that subarachnoid hemorrhage increases the penetration of nicardipine from vessels into the subarachnoid space.

Hippocampal unit activity after transient cerebral ischemia in rats

Single unit activity of CA1 and CA3 neurons in the hippocampus was recorded in rats 1, 2, or 3 days after 10 minutes of transient cerebral ischemia induced by the clamping of both carotid arteries combined with hypotension. In addition, paired pulse inhibition/facilitation of the CA1 population spike was examined on Day 2 using two successive stimuli of the contralateral CA3 region delivered at various intervals. On Day 1, the mean +/- SEM firing rate in the CA1 region was 0.91 +/- 0.42/sec (n = 5), which was not significantly different from the control value of 0.98 +/- 0.26/sec (n = 5). Firing rate increased on Days 2 and 3 to 3.96 +/- 0.69/sec (n = 5), and 6.49 +/- 0.89/sec (n = 5), respectively. In the CA3 region, the mean +/- SEM firing rate of 1.18 +/- 0.27/sec in the five control rats sharply dropped to 0.14 +/- 0.11/sec in the five Day 1 rats and gradually increased to 0.45 +/- 0.11/sec in the five Day 3 rats. Histologic examination of these rats revealed ischemic changes restricted to CA1 neurons on Days 2 and 3. The paired-pulse experiment showed no significant difference between six control and six Day 2 rats in the inhibition of the second population spike with interstimulus intervals of less than 400 msec. At interstimulus intervals of greater than 500 msec there was facilitation of the second spike, which lasted 5 seconds in Day 2 rats. This facilitation was not observed in control rats. Because CA3 neurons constitute the main input to CA1 pyramidal cells, decreased activity of CA3 neurons indicates less excitatory input to CA1 neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors associated with hydrocephalus after subarachnoid hemorrhage. A report of the Cooperative Aneurysm Study

Hydrocephalus is an important complication of subarachnoid hemorrhage (SAH). We analyzed several factors possibly related to hydrocephalus following SAH in 3521 patients from the International Study on the Timing of Aneurysm Surgery. Hydrocephalus was diagnosed on admission computed tomographic (CT) scans in 15% of patients and was thought to be clinically symptomatic in 13.2% of patients. There was a 5.9% overlap between these groups. Using contingency table analysis, we found the following were significantly related to clinical hydrocephalus: increasing age; preexisting hypertension; admission blood pressure measurements; postoperative hypertension; admission CT findings of intraventricular hemorrhage, a diffuse collection of subarachnoid blood, and a thick focal collection of subarachnoid blood; posterior circulation site of aneurysm; focal ischemic deficits; use of antifibrinolytic drugs preoperatively; hyponatremia; admission level of consciousness; and a low score on the Glasgow outcome scale. Using discriminate factor analysis to predict clinical hydrocephalus, the most important variables in order were the following: CT hydrocephalus, intraventricular hemorrhage, admission level of consciousness, presubarachnoid hypertension, increasing age, subarachnoid blood noted on CT scan, posterior circulation aneurysm site, and hypertension postoperatively (canonical correlation = .399). We conclude that the development of hydrocephalus after SAH is multifactorial. Factors that compromise cerebrospinal fluid circulation acutely (eg, intraventricular hemorrhage, hemorrhage from a posterior circulation site of aneurysm, and diffuse spread of subarachnoid blood) contribute to the development of acute hydrocephalus. These same factors, plus the use of antifibrinolytic drugs preoperatively, are also important in the pathogenesis of clinical hydrocephalus, perhaps by promoting subarachnoid fibrosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of muscarinic cholinergic receptors on the endothelium and the smooth muscle of the rabbit thoracic aorta

Pharmacodynamic and quantitative autoradiographic studies were performed to characterize the muscarinic receptors on the endothelium and smooth muscle of the rabbit thoracic aorta. The antagonistic effect of atropine and pirenzepine on the relaxation induced by acetylcholine showed that the relaxation was mediated by muscarinic receptors with pA2 values of 9.4 and 6.6, respectively, suggesting the presence of muscarinic receptors on the endothelium with low affinity for pirenzepine. The quantitative autoradiographic study using [3H]-propylbenzilylcholine mustard (3H-PrBCM) showed that the specific 3H-PrBCM binding was time dependent and saturable. Saturation times of the bindings were not significantly different between the receptors on the endothelium and those on the smooth muscle layer. The density of the receptors was higher in the smooth muscle layer than in the endothelium. The specific [3H]-quinuclidinyl benzilate (3H-QNB) binding was displaced by atropine or pirenzepine dose dependently. IC50 of pirenzepine for the receptors on the endothelium was not significantly different from that for the receptors on the smooth muscle layer. These findings suggest that there is a smaller density of muscarinic receptors on the endothelium than on the smooth muscle layer of the rabbit thoracic aorta. The muscarinic receptors on the endothelium can be subclassified into the same subtype as the receptors on the smooth muscle layer, which have low affinity for pirenzepine.

The influence of experimental subarachnoid hemorrhage on the relaxation induced by vasoactive intestinal polypeptide in the cerebral arteries of the rabbit

The influence of subarachnoid hemorrhage (SAH) on vasodilatation induced by vasoactive intestinal polypeptide (VIP) was investigated in rabbit basilar arteries. VIP-induced relaxation was measured in ring sections of the basilar arteries precontracted by 10(-5) M serotonin using an isometric tension recording method. The cyclic adenosine monophosphate (cAMP) content was measured using radioimmunoassay as an indicator of the intracellular mechanism in the arterial smooth muscle cells. VIP (10(-11)-10(-6) M) evoked dose-dependent relaxation of the basilar arteries. The relaxation achieved with 10(-6) M VIP was 85 +/- 4% (n = 7) of the initial contractile tone in control arteries and 47 +/- 5% (n = 8) in the arteries evaluated 2 days after SAH, suggesting that VIP-induced relaxation was suppressed significantly after SAH (P less than 0.01). The cAMP content was significantly higher in the basilar arteries 2 days after SAH (425 +/- 48 pmol/g of tissue, n = 7) than in the control basilar arteries (194 +/- 57 pmol/g of tissue, n = 7). In normal arteries, the cAMP content was increased to a significant degree by VIP (10(-6) M) (325 +/- 60% of control cAMP content, n = 5), whereas the increase was less in the arteries evaluated 2 days after SAH (112 +/- 16% of control cAMP content, n = 5). These results suggest that SAH has an influence on cAMP metabolism in the arteries and that SAH impairs the postsynaptic mechanism of VIP-induced dilatation of the arteries.

Effect of intracisternal antithrombin III on subarachnoid hemorrhage-induced arterial narrowing

The ability of antithrombin III, an endogenous plasma glycoprotein, to reverse the arterial narrowing in a rabbit model of cerebral vasospasm was evaluated. The vasodilator activity of antithrombin III on rabbit arteries was first assessed in vitro using a myograph-arterial ring preparation. Antithrombin III (10 IU/ml) induced a 55.4% +/- 2.66% (mean +/- standard error of the mean) relaxation in basilar artery precontracted with serotonin (5-HT) in five specimens as compared with a 9.8% +/- 1.6% relaxation of common carotid artery in six specimens. For in vivo analysis, 21 New Zealand White male rabbits were separated into three groups: Group 1 served as normal controls; Group 2 received a subarachnoid blood injection (SAH) and were sacrificed on Day 3 thereafter; and Group 3 animals were subjected to SAH, then received a 2-hour intracisternal infusion of antithrombin III (100 IU) in saline prior to sacrifice on Day 3. Basilar artery caliber was determined using a morphometric method to analyze perfusion-fixed arterial segments. Control basilar artery diameter in Group 1 was 0.64 +/- 0.02 mm. In Group 2 a 27% reduction in arterial caliber to 0.47 +/- 0.03 mm was observed by Day 3 post SAH (p less than 0.0001). Group 3 animals had a mean basilar artery diameter of 0.68 +/- 0.02 mm. This was significantly larger than the untreated SAH rabbits in Group 2 (p less than 0.0001), but not different from control artery diameters in Group 1. The findings demonstrate that antithrombin III in saline has a significant ability to reverse delayed narrowing of the rabbit basilar artery after SAH.

Effect of the nonglucocorticoid 21-aminosteroid U74006F experimental cerebral vasospasm

The present work was performed to establish whether the nonglucocorticoid, 21-aminosteroid, U74006F, could prevent the development of delayed cerebral vasospasm after experimental subarachnoid hemorrhage. The subarachnoid hemorrhage was produced by percutaneous injection of 4.5 mL of nonheparinized autologous blood into the cisterna magna of rabbits. U74006F (1 mg/kg) or placebo was injected intraperitoneally every 12 hours starting 12 hours prior to induction of hemorrhage for a total of six doses. The animals were sacrificed by perfusion fixation. The basilar artery was removed on day 2 and processed for morphometric analysis. Control/placebo and subarachnoid hemorrhage/placebo basilar artery diameters were 651.2 +/- 25.4 and 366.3 +/- 34.2 mu, respectively. Control/U74006F basilar artery diameters (669.8 +/- 21.8 mu) were not significantly different from that of the control/placebo group. U74006F treatment greatly minimized subarachnoid hemorrhage-induced reduction in mean luminal diameter (563.7 +/- 48.2 mu) (p less than 0.001). These results demonstrate considerable therapeutic promise for U74006F in the prevention of cerebral vasospasm.

Blood-arterial wall barrier disruption to various sized tracers following subarachnoid haemorrhage

Disruption of the blood-arterial wall barrier in the major cerebral arteries occurs following subarachnoid haemorrhage (SAH) and may be related to the pathogenesis of cerebral vasospasm. Using FITC dextrans of various sizes, the present study was undertaken to determine if the barrier disruption shortly after SAH occurs equally to various sized tracers. Forty-two Sprague-Dawley rats were divided into 5 groups. Four groups were injected with FITC-dextrans of differing molecular weights (MW): FD4 (MW = 4,080), FD 40 (MW = 40,500), FD 70 (MW = 71,400), and FD 150 (MW = 156,900). One group was injected with horseradish peroxidase (HRP: MW = 40,000). Each group was further divided into two subgroups: with or without SAH. SAH was induced by injecting arterial blood into the cisterna magna. To assess the integrity of the blood-arterial wall barrier by transmission electron microscope, the tracers were intravenously injected prior to sacrificing the animals. The groups without SAH showed no permeability of tracers into the subendothelial spaces of the basilar arteries. In contrast, with the exception of FD 150, FITC-dextrans (FD 4, FD 40, FD 70) were noticed in the subendothelial spaces. The distribution of FITC-dextrans in the elastic lamina was similar to that of HRP. These results suggest that barrier disruption occurs with a wide range of molecular sizes of FITC-dextrans, although there seems to be some limitation to the permeation of the larger molecules. The present study suggests that the mechanism of barrier disruption of the major cerebral arteries in the acute stage following SAH may be vesicular rather than by separation of tight junctions.

Deep cerebral venous thrombosis. Clinical, neuroradiological, and neuropsychological correlates

Thrombosis of the deep cerebral venous system is usually fatal, and patients are frequently stuporous or comatose at presentation. This report describes serial radiological and neuropsychological observations in an 18-year-old woman who remained alert and survived this disorder. In association with diencephalic edema seen on computed tomographic scan, she demonstrated disorientation, abulia, attentional deficits, memory loss, and dyscalculia and had impaired IQ scores: the performance scores were worse than the verbal scores. Significant aphasia or sensory loss was absent. She recovered full intellectual capacity in the course of follow-up examinations, and the diencephalic edema seen on the computed tomographic scan resolved despite persistent thrombosis of the straight sinus demonstrable on follow-up digital angiography.

Effect of hypoxia on endothelium-dependent relaxation of canine and rabbit basilar arteries

An important role of endothelium-dependent relaxation in the local regulation of vascular tone has been suggested. In the present study, the effect of hypoxia on endothelium-dependent relaxation was investigated in canine and rabbit basilar and in rabbit common carotid arteries in vitro, using an isometric tension recording method. Hypoxia was introduced by changing the gas mixture in the in vitro chamber from 95% O2-5% CO2 to 95% N2-5% CO2. Thrombin and acetylcholine were used to induce endothelium-dependent relaxation. Thrombin at 0.1 and 1.0 U/ml, respectively, caused dose-dependent relaxation of the canine basilar artery precontracted by 10(-6)M prostaglandin F2 alpha. Acetylcholine also evoked dose-dependent relaxation of rabbit basilar and common carotid arteries precontracted by serotonin. Under hypoxic conditions, the relaxing effect of thrombin or acetylcholine decreased both in canine and in rabbit arteries, although it was not significant in rabbit basilar arteries. It has been postulated that following subarachnoid haemorrhage, diffusion of oxygen to the walls of the major cerebral arteries might be impaired by the subarachnoid clot. This could cause hypoxia of the arteries and contribute to vasospasm by suppressing endothelium-dependent relaxation, as well as by enhancing the contractile responses of the cerebral arteries to the vasoconstrictor agents in the bloody cerebrospinal fluid.

Rapid increase of prostaglandin F2-alpha in neurons after subarachnoid hemorrhage in rats: an immunohistochemical study

The effects of subarachnoid hemorrhage (SAH) with various degrees of increase in intracranial pressure (ICP) on the staining of prostaglandin F2-alpha (PG F2alpha) were studied in rat brains. SAH was produced in 18 rats by injection of 0.18-0.20 ml of autologous arterial blood/100 g body weight into the cisterna magna. By changing the speed of injection, the ICP was transiently increased by 346 +/- 68 (mean +/- S.D.) mm Hg in eight rats (including three pretreated with indomethacin), by 200 +/- 42 mm Hg in five rats, and by 6 +/- 4 mm Hg in the other five. Three rats injected with the same volume of mock cerebrospinal fluid (CSF) with ICP increased by 217 +/- 67 mm Hg and five normal rats without injection served as controls. All animals were decapitated 15 min after injection. The cryosections were stained for PG F2 alpha using an indirect immunofluorescence method. Positive staining for PG F2 alpha was noted only in pial vessels in all normal and mock-CSF-injected rats. In SAH rats with ICP increased by 6 +/- 4 mm Hg, there was a positive reaction in hippocampal neurons and Purkinje cells as well as blood vessels. SAH rats with higher ICP showed stronger PG F2 alpha staining in the above areas, as well as in cerebellar granule cells. All rats pretreated with indomethacin showed a smaller increase in staining. The above results indicate that subarachnoid blood clots per se produce a rapid increase of PG F2 alpha in neurons and blood vessels of both cerebrum and cerebellum, and that this increase is augmented by intracranial hypertension.

Effect of subarachnoid hemorrhage on calcitonin gene-related peptide-induced relaxation in rabbit basilar artery

An isometric tension measurement of ring segments was performed in the rabbit basilar and common carotid arteries in vitro to investigate the regional differences in the calcitonin gene-related peptide (CGRP)-induced vasodilation and the effect of subarachnoid hemorrhage on CGRP-induced vasodilation. CGRP elicited vasodilation of the rabbit basilar artery in a dose-dependent fashion when the artery was precontracted by 10(-5) M 5-hydroxytryptamine, whereas almost no relaxation occurred in the rabbit common carotid artery. The relaxation of the basilar artery was 64.03 +/- 1.85% at 3 x 10(-8) M CGRP, with an EC50 of 8.46 +/- 0.08. Two days after experimental subarachnoid hemorrhage, CGRP-induced relaxation of the rabbit basilar artery was 53.96 +/- 8.08% of the 10(-5) M 5-hydroxytryptamine-induced contraction, not significantly different from that of the basilar artery of the control rabbit. Our findings suggest that CGRP induces potent vasodilation in the rabbit basilar artery and that no impairment of vasodilation occurred after experimental subarachnoid hemorrhage. We speculate that CGRP may have therapeutic potential in cerebrovascular disease such as vasospasm after subarachnoid hemorrhage.

Immunohistochemically demonstrated increase of prostaglandin F2-alpha in neurons after reoxygenation in anoxic rats

Immunohistochemical staining for prostaglandin F2-alpha (PG F2 alpha) was conducted to identify PG F2 alpha synthesizing or binding sites in anoxic rat brains. Anoxia was produced in 22 rats to lower the arterial oxygen tension (PaO2) to 21 +/- 4 mmHg by ventilation with a 95% nitrogen and 5% carbon dioxide gas mixture. In 8 animals anoxia was continued for 30 sec, and in 14 rats for 3 min. Prior to decapitation, 5 animals in the 30-sec anoxia group and 8 rats in the 3-min anoxia group were reoxygenated for 5 min, while the remaining 9 were not. Five-min reoxygenation returned the PaO2 to 106 +/- 7. Three non-reoxygenated and 3 reoxygenated rats, all pretreated with indomethacin, and 5 normal rats served as controls. The brains were snap-frozen. The cryosections were stained by the indirect immunofluorescence method. PG F2 alpha was noted mainly in pial vessels in all normal rats. All reoxygenated rats showed a positive reaction not only in blood vessels, but also in neurons, particularly hippocampal neurons and Purkinje cells. The staining of the above neurons was noted to be less in non-reoxygenated rats. The stronger staining was observed in rats reoxygenated after 3-min anoxia than 30-sec anoxia. The indomethacin-pretreated rats showed almost no increase in staining intensity. The above results indicate that reoxygenation after anoxia results in an increase of PG F2 alpha in neurons of both cerebrum and cerebellum.

Comparison of intraluminal and extraluminal inhibitory effects of hemoglobin on endothelium-dependent relaxation of rabbit basilar artery

To determine whether extraluminal or intraluminal hemoglobin inhibits endothelium-dependent relaxation, we measured the vascular responsiveness of rabbit basilar artery in an in vitro perfusion system and we performed immunohistochemical staining for hemoglobin. In the in vitro study, we applied agents from either the intraluminal or the extraluminal side of excised basilar arteries. KCl-induced contraction was the same with either application. Acetylcholine-induced maximal relaxations were 57.6 +/- 8.5% of the contraction induced by 10(-5) M 5-hydroxytryptamine for control, 3.3 +/- 0.3% for intraluminal, and 34.9 +/- 8.6% for extraluminal applications. Adenosine triphosphate-induced maximal relaxations were 64.2 +/- 4.1% of the contraction induced by 10(-5) M 5-hydroxytryptamine for control, 26.9 +/- 3.8% for intraluminal, and 42.2 +/- 6.0% for extraluminal applications. Hemoglobin's inhibition of acetylcholine- and adenosine triphosphate-induced relaxation was significantly greater with intraluminal than with extraluminal application (p less than 0.05). The immunohistochemical study revealed hemoglobin in the outer layer of the smooth muscle and in the adventitia when 10(-5) M hemoglobin was applied extraluminally for 5 minutes, whereas hemoglobin was observed on the surface of the endothelial cells after intraluminal application. Our findings suggest that hemoglobin inhibits acetylcholine- or adenosine triphosphate-induced relaxation by binding to endothelium-derived relaxing factor (EDRF) and by inhibiting production of EDRF. Hemoglobin's inhibitory effect on endothelium-dependent relaxation may be important in the pathogenesis of vasospasm after subarachnoid hemorrhage.

Pharmacological comparison of endothelium-dependent relaxation in isolated cerebral and extracerebral arteries

Endothelium-dependent relaxation was induced by acetylcholine (ACh), adenosine triphosphate (ATP), and thrombin in isolated cerebral and extracerebral arteries obtained from rabbits and dogs. Using an isometric tension-recording method, the authors then examined the difference in the extent of relaxation between the cerebral and extracerebral arteries. In rabbits, the dose-response curve of the basilar artery for ACh was significantly different (p less than 0.05) from curves of the femoral and common carotid arteries. The IC50 value (the concentration inducing a one-half inhibition of the initial contractile tone) for the basilar artery in ACh-induced relaxation was significantly higher (p less than 0.05) than for the common carotid artery, although the mean maximum relaxation of the basilar artery to ACh was not significantly different from that seen in extracerebral arteries. The relaxing effect of ACh in dogs was much less in the middle cerebral and basilar arteries than in the common carotid, vertebral, and femoral arteries. On the other hand, both ATP (in rabbits and dogs) and thrombin (in dogs) induced significantly more (p less than 0.05) relaxation in the cerebral arteries than in the extracerebral arteries. Endothelium-dependent relaxation induced by ACh or ATP has been demonstrated in a wide range of arteries from a variety of animals. The present results suggest that ATP has a more important role than ACh in the regulation of the vascular tone of the major cerebral arteries in these two species.