LF 16-0687 Ms,a bradykinin B2 receptor antagonist,reduces brain edema and improves long-term neurological function recovery after closed head trauma in rats

Bradykinin is an endogenous inflammatory agent that enhances vascular permeability and produces tissue edema. We investigated whether LF 16-0687 Ms, a potent nonpeptide antagonist of bradykinin type-2 (B(2)) receptor, was able to reduce brain swelling and to improve the recovery of neurological function following closed head trauma (CHT) in rats. In dose-effect studies, LF 16-0687 Ms doses of 0.75-4.5 mg/kg given 1 h after trauma significantly reduced the development of edema in the injured hemisphere by a maximum of 70%. It had no effect on the brain water content of sham-operated rats. LF 16-0687 Ms also significantly improved neurological recovery evaluated by a Neurological Severity Score (NSS) based on motor, reflex, and behavioral tests. In time-window studies LF 16-0687 Ms (2.25 mg/kg) was given 1, 2, 4, and 10 h after CHT. The extent of edema was significantly reduced when LF 16-0687 Ms was given 1 h (-45%), 2 h (-52%), and 4 h (-63%) but not 10 h (-24%) after CHT. Given at any time-point, LF 16-0687 Ms significantly improved the recovery of the NSS at 24 h. In duration of treatment studies, rats tended to recover normal neurological function over 14 days after CHT. However, time to recovery was longer in severely than in moderately injured animals, unless they were treated with LF 16-0687 Ms. This study provides further evidence that blockade of bradykinin B(2) receptors represents a potential effective approach to the treatment of focal cerebral contusions.     

Riluzole reduces brain swelling and contusion volume in rats following controlled cortical impact injury

Modulation of the glutamatergic and excitotoxic pathway may attenuate secondary damage following traumatic brain injury by reducing presynaptic glutamate release and blocking sodium channels in their inactivated state. The aim of the present study was to investigate the neuroprotective potential of riluzole in traumatic brain-injured rats. A left temporoparietal contusion was induced in 70 male Sprague-Dawley rats (controlled cortical impact injury). Riluzole (8 mg/kg body weight) was given 30 min, and 6, 24, and 30 h after trauma, while control rats received physiological saline. Experiments were performed at two different degrees of trauma severity as defined by penetration depth of the impactor rod (1 vs. 1.5 mm) with the aim of investigating impact of severity of tissue damage on the neuroprotective potential of riluzole. At 48 h after trauma, brains were removed to determine hemispheric swelling and water content and to assess cortical contusion volume. Before brain removal cisternal cerebrospinal fluid (CSF) was collected in all rats to determine the effects of riluzole on substances associated with edema formation. For this, the excitatory transmitter glutamate, the volume-regulatory amino acid taurine, and the ATP-degradation product hypoxanthine were analyzed by high-performance liquid chromatography. Overall, the degree of tissue damage seems to influence the neuroprotective potential of riluzole. In rats with a less severe trauma (1-mm penetration depth), hemispheric swelling, cerebral water content of the traumatized hemisphere and cortical contusion volume were significantly reduced under riluzole compared to controls (p < 0.05). In rats with a more severe trauma (1.5-mm penetration depth), the neuroprotective effect of riluzole failed to reach statistical significance. Following trauma, CSF glutamate, taurine, and hypoxanthine levels were significantly increased compared to nontraumatized rats (p < 0.001). However, these neurochemical parameters as measured in cisternal CSF failed to reflect trauma-dependent increases in severity of tissue damage and did not reveal riluzole-mediated neuroprotection. Under the present study design, riluzole significantly reduced brain edema formation and contusion volume in rats subjected to a mild focal cortical contusion.     

Role of bradykinin B2 receptors in the formation of vasogenic brain edema in rats.

Bradykinin is a mediator of brain edema acting through B2 receptors. However, it is not known if bradykinin mediates the formation of cytotoxic or vasogenic brain swelling. To investigate this question we subjected rats to a cryogenic brain lesion over the left parietal cortex, a model well known to produce predominantly vasogenic brain edema. We inhibited bradykinin B2 receptors with the recently characterized nonpeptide B2 receptor antagonist, LF 16-0687. The animals were assigned to three groups (n = 10, each) receiving 10, or 100 microg/kg/min LF 16-0687 or vehicle (0.9% NaCl). Treatment started 15 min before trauma and was continued for 24 h. Another three groups of animals (n = 10, each) received 10 microg/kg/min LF 16-0687 starting 30 or 60 min after trauma or vehicle (0.9% NaCl) for 24 h. Animals were then sacrificed and swelling and water content of the brain were determined. In the vehicle treated group the traumatized hemisphere swelled by 9.3 +/- 1.1% as compared to the untraumatized contralateral side. Pretreatment with 10 microg/kg/min LF 16-0687 decreased brain swelling significantly to 6.4 +/- 1.3% (p < 0.05). Pre-treatment with 100 microg/kg/min was found to be less effective and did not result in a significant reduction of brain swelling (7.4 + 1.3%). Treatment with LF 16-0687 for 24 h (10 microg/kg/min) started 30 or 60 min after trauma did not reduce brain water content or hemispheric swelling. These results demonstrate that brain injury-mediated bradykinin production induces vasogenic brain edema by B2 receptor stimulation. Our findings further clarify the role of bradykinin in the pathophysiology of brain edema formation and confirm the therapeutic potency of bradykinin B2 receptor inhibition.     

LF 16-0687 Ms,a new bradykinin B2 receptor antagonist,improves neurologic outcome but not brain tissue prostaglandin E2 release in a rat model of closed head trauma combined with ethanol intoxication

BACKGROUND: LF 16-0687 Ms previously was reported to improve Neurological Severity Score (NSS) and decrease cerebral edema and prostaglandin E(2) (PGE(2)) release after closed head trauma (CHT) in rats. Here, we examined whether these beneficial effects of LF 16-0687 Ms are altered when CHT is accompanied by acute ethanol administration. METHODS: Six groups of rats (n = 8 per group) were examined during combination of the following experimental conditions: CHT versus sham operation, LF 16-0687 Ms 3 mg/kg subcutaneously versus saline, and ethanol 2 g/kg versus saline. RESULTS: After CHT, brain water content decreased and NSS improved with ethanol + LF 16-0687 Ms as compared with values after saline or ethanol. PGE(2) release decreased with ethanol (147 +/- 59 pg/mg tissue) but not with ethanol + LF 16-0687 Ms (286 +/- 194 pg/mg tissue). CONCLUSION: Ethanol does not affect the improvement of NSS and the decrease of cerebral edema seen with LF 16-0687 Ms after CHT, but does reverse the ability of LF 16-0687 Ms to minimize the increase of PGE(2) release. In intoxicated patients, bradykinin antagonist therapy may improve post-CHT outcome without altering PGE(2) release.     

The importance of kinin antagonist treatment timing in closed head trauma.

BACKGROUND: Giving LF 16-0687 Ms (a bradykinin B2 receptor antagonist) 1 hour after closed head trauma (CHT) previously was reported to decrease brain edema at 24 hours and improve neurologic severity score (NSS) at 7 days. It is not certain whether a greater benefit could be achieved by treatment sooner after CHT. METHODS: To examine the latter possibility we studied a surrogate condition for the earliest possible administration of LF 16-0687 Ms after CHT, e.g., we examined brain edema and NSS when LF 16-0687 Ms was given 15 min before CHT in rats. RESULTS: LF 16-0687 Ms decreased brain water content (80.0 +/- 1.4%, mean +/- SD) at 24 hours and improved NSS (2 +/- 3, median +/- range) at 7 days after CHT in comparison to that with CHT + saline (82.9 +/- 1.3% and 8 +/- 4). CONCLUSION: Similarity of the present results to those previously reported indicates that the benefit of giving LF 16-0687 Ms 1 hour after CHT appears to represent the maximal benefit afforded by this drug.     

Glutamate and taurine are increased in ventricular cerebrospinal fluid of severely brain-injured patients

Glutamate contributes to secondary brain damage, resulting in cell swelling and brain edema. Under in vitro conditions, increased extracellular levels of the amino acid taurine reflect glutamate-induced osmotic cell swelling. In vivo, increases in cerebrospinal fluid (CSF) taurine could, therefore, unmask glutamate-mediated cytotoxic edema formation and possibly differentiate it from vasogenic edema. To test this hypothesis, ventricular CSF glutamate and taurine levels were measured in 28 severely brain-injured patients on days 1, 5, and 14 after trauma. Posttraumatic changes in CSF amino acids were investigated in regard to extent of tissue damage and alterations in brain edema as estimated by computerized tomography. On day 1, CSF glutamate and taurine levels were significantly increased in patients with subdural or epidural hematomas (8+/-0.8/71+/-12 microM), contusions (21+/-4.1/122+/-18 microM), and generalized brain edema (13+/-3.2/80+/-15 microM) compared to lumbar control CSF (1.3+/-0.1/12+/-1 microM; p < 0.001). CSF amino acids, however, did not reflect edema formation and resolution as estimated by computerized tomography. CSF taurine correlated positively with glutamate, eventually depicting glutamate-induced cell swelling. However, parallel neuronal release of taurine with its inhibitory function cannot be excluded. Thus, the sensitivity of taurine in unmasking cytotoxic edema formation is weakened by the inability in defining its origin and function under the conditions chosen in the present study. Overall, persisting pathologic ventricular CSF glutamate and taurine levels are highly suggestive of ongoing glial and neuronal impairment in humans following severe traumatic brain injury.     

Effect of LF 16-0687MS, a new nonpeptide bradykinin B2 receptor antagonist, in a rat model of closed head trauma

Bradykinin is an endogenous nonapeptide which potently dilates the cerebral vasculature and markedly increases vascular permeability. These effects are mediated by B2 receptors located on the vascular endothelium. Previous experimental studies have shown that blockade of the kallikreinkinin system, which mediates the formation of bradykinin, afforded a reduction of the brain edema that developed following a cryogenic cortical lesion. In the present study, we investigated the effect of LF 16-0687MS, a novel nonpeptide B2 receptor antagonist, on cerebral edema and neurological severity score (NSS) after closed head injury to rats. LF 16-0687MS or its vehicle (NaCl 0.9%) was continuously infused at 10, 30, and 100 microg/kg/min over 23 h starting 1 h after a focal trauma to the left hemisphere was induced using a weight-drop device. The extent of edema formation was evaluated 24 h after trauma from left and right hemispheres samples by measurement of specific gravity and water content. In a separate study, a neurological severity score based on scoring of behavioural and motor functions was evaluated 1 h and over 1 week after trauma. LF 16-0687MS at 100 microg/kg/min markedly reduced the development of brain edema as indicated by a 68% increase in specific gravity (p<0.05) and a 64% decrease of water content (p<0.05) in the left hemisphere. In addition the recovery of neurological function was significantly improved by 100 microg/kg/min LF 16-0687MS from day 3 to day 7 after CHT. In a separate experiment, we also showed that LF 16-0687MS at 100 microg/kg/min given either 1 h before or 30 min after CHT did not affect mean arterial blood pressure. These results show that blockade of bradykinin B2 receptors is an effective approach to reduce cerebral edema and to improve neurological outcome after a focal contusion to the cranium.     

Detrimental role of bradykinin B2 receptor in a murine model of diffuse brain injury

Inhibition of the bradykinin B2 receptor type (B2R) has been shown to improve neurological outcome in models of focal traumatic brain injury. However, the involvement of B2R in trauma-induced diffuse injury has not yet been explored. This is an important point, since in humans a pattern of diffuse injury is commonly found in severely injured patients and has been associated with a poor neurological outcome and prognosis. Using the non-peptide B2R antagonist LF 16-0687 Ms and B2R null (B2R-/-) mice, we investigated the role of B2R in a model of closed head trauma (CHT). LF 16-0687 Ms given 30 min after injury reduced the neurological deficit by 26% and the cerebral edema by 22% when evaluated 4 h after CHT. Neurological function after CHT was improved in B2R-/- mice compared to B2R+/+ mice, although there was no difference in the development of brain edema. Treatment with LF 16-0687 Ms and B(2)R gene deletion decreased the accumulation of neutrophils at 24 h after CHT (50% and 36%, respectively). In addition, the inducible NO synthase (iNOS) mRNA level increased markedly, and this was reduced by LF 16-0687 Ms. Taken together, these data support a detrimental role of B2R in the development of the neurological deficit and of the inflammatory secondary damage resulting from diffuse traumatic brain injury. Therefore, blockade of bradykinin B2 receptors might represent an attractive therapeutic approach in the pharmacological treatment of traumatic brain injury.     

Effects of tacrolimus on hemispheric water content and cerebrospinal fluid levels of glutamate, hypoxanthine, interleukin-6, and tumor necrosis factor-alpha following controlled cortical impact injury in rats

OBJECT: Disturbance of calcium homeostasis contributes to evolving tissue damage and energetic impairment following traumatic brain injury (TBI). Calcium-mediated activation of calcineurin results in production of tissue-damaging nitric oxide and free oxygen radicals. Inhibition of calcineurin induced by the immunosuppressant tacrolimus (FK506) has been shown to reduce structural and functional damage after ischemia. The aims of the present study were to investigate time- and dose-dependent short-term antiedematous effects of tacrolimus following TBI. METHODS: A left temporoparietal contusion (controlled cortical impact injury [CCII]) was induced in 51 male Sprague-Dawley rats. Tacrolimus (1 or 3 mg/kg body weight) was administered by a single intraperitoneal injection at 5 minutes, 30 minutes, or 4 hours after CCII occurred. Control rats received physiological saline. Water contents of traumatized and nontraumatized hemispheres, as well as cerebrospinal fluid (CSF) levels of mediators reflecting tissue damage (the proinflammatory cytokines interleukin [IL]-6 and tumor necrosis factor [TNF]-alpha, the excitotoxin glutamate, and the adenosine triphosphate-degradation product hypoxanthine), were determined 24 hours after trauma. Although CSF levels of IL-6 and TNFalpha were completely suppressed by tacrolimus at all time points and at both concentrations, CSF levels of glutamate and hypoxanthine, as well as edema formation, were only marginally influenced. Significant reduction of cerebral water content was confined to nontraumatized hemispheres. In addition, the higher dose of tacrolimus failed to exert significant antiedematous effects on traumatized hemispheres. CONCLUSIONS: Under the present study design, the potency of tacrolimus in reducing edema formation following CCII seems limited. However, its immunosuppressive effects could be of value in influencing the posttraumatic inflammatory response known to aggravate tissue damage.     

Effect of an anion transport inhibitor, L-644,711, on brain injury and edema after temporary middle cerebral artery occlusion in rats

The affect of L-644,711, an anion transport inhibitor, on ischemic brain injury and edema was investigated. Spontaneously hypertensive rats were given one of the following doses of intrathecal L-644,711 during 180 min of middle cerebral artery occlusion and 120 min of reperfusion: control, vehicle only; dose I, 100 microg/kg: dose II, 200 microg/kg; dose III, 250 mug/kg; or dose IV, 320 microg/kg. Immediately after the 5-h period of ischemia and reperfusion, the brains were analyzed for brain injury with 2,3,5-triphenyltetrazolium chloride, and for edema by microgravimetry (specific gravity). There were no between-group differences in specific gravity (brain water content). Brain injury (% of the hemisphere ipsilateral to middle cerebral artery occlusion) was less (p <0.05) in rats that received the 250 (35 +/- 5%, mean +/- SD) or 320 microg/kg (36 +/- 6%) doses of L-644,711 vs. the control group (47 +/- 5%). L-644,711 has been hypothesized to affect brain injury by improving the neuronal acid-base state, inhibiting astroglial swelling, decreasing neutrophil aggregation, or reducing glutamate release. The microgravimetric data do not support astroglial swelling as a primary mechanism of decreased brain injury.     

Effects of magnesium administration on brain edema and blood-brain barrier breakdown after experimental traumatic brain injury in rats

In this study, we examined the effects of magnesium sulfate administration on brain edema and blood-brain barrier breakdown after experimental traumatic brain injury in rats. Seventy-one adult male Sprague-Dawley rats were anesthetized, and experimental closed head trauma was induced by allowing a 450-g weight to fall from a 2-m height onto a metallic disk fixed to the intact skull. Sixty-eight surviving rats were randomly assigned to receive an intraperitoneal bolus of either 750 micromol/kg magnesium sulfate (group 4; n = 30) or 1 mL of saline (group 2; n = 30) 30 minutes after induction of traumatic brain injury; 39 nontraumatized animals received saline (group 1; n = 21) or magnesium sulfate (group 3; n = 18) with an identical protocol of administration. Brain water content and brain tissue specific gravity, as indicators of brain edema, were measured 24 hours after traumatic brain injury. Blood-brain barrier integrity was evaluated quantitatively 24 hours after injury by spectrophotometric assay of Evans blue dye extravasations. In the magnesium-treated injured group, brain water content was significantly reduced (left hemisphere: group 2, 83.2 +/- 0.8; group 4, 78.4 +/- 0.7 [P <.05]; right hemisphere: group 2, 83.1 +/- 0.7; group 4, 78.4 +/- 0.5. [P <.05]) and brain tissue specific gravity was significantly increased (left hemisphere: group 2, 1.0391 +/- 0.0008; group 4, 1.0437 +/- 0.001 [P <.05]; right hemisphere, group 2, 1.0384 +/- 0.001; group 4, 1.0442 +/- 0.005 [P <.05]) compared with the saline-treated injured group. Evans blue dye content in the brain tissue was significantly decreased in the magnesium-treated injured group (left hemisphere: group 2, 0.0204 +/- 0.03; group 4, 0.0013 +/- 0.0002 [P <.05]; right hemisphere: group 2, 0.0064 +/- 0.0009; group 4, 0.0013 +/- 0.0003 [P <.05]) compared with the saline-treated injured group. The findings of the present study support that beneficial effects of magnesium sulfate exist after severe traumatic brain injury in rats. These results also indicate that a blood-brain barrier permeability defect occurs after this model of diffuse traumatic brain injury, and magnesium seems to attenuate this defect.     

Ketamine decreases cerebral infarct volume and improves neurological outcome following experimental head trauma in rats

In brain injury, concentrations of extracellular excitatory amino acids are increased and stimulate glutamate receptors in general and the N-methyl-D-aspartate (NMDA)-preferring subtype in particular. That stimulation causes substantial calcium influx, which appears to initiate a cascade of events leading to neuronal death. Blockage of NMDA receptors with specific antagonists or noncompetitive ion channel blockers provides protection against excitatory amino acid-induced neurotoxicity. We previously reported that the NMDA receptor antagonist dizocilpine maleate improved the neurological severity score (NSS) after head trauma in rats. The present study was designed to determine whether ketamine, a NMDA receptor antagonist like dizocilpine maleate, improves neurological outcome following head trauma in rats. Thirty-two male Sprague-Dawley rats (235-250 g) were divided into four groups. Groups A and B were surgically prepared only. Groups C and D were surgically prepared and then a nonpenetrating impact was delivered to the cranium over the left hemisphere. Groups A and C received no treatment. Groups B and D were treated with ketamine, 180 mg/kg i.p., 1 h after head trauma. The NSS was determined at 1, 2, 4, 10, 24, and 48 h following head trauma. After killing at 48 h, cortical slices were taken adjacent to the lesion on the traumatized hemisphere and from comparable sites on the nontraumatized hemisphere to measure the tissue specific gravity and water content. Brains were then placed in 4% formaldehyde and the volume of hemorrhagic necrosis measured 4 days later. Head trauma increased the NSS and, in the traumatized hemisphere, decreased the specific gravity, increased the water content, and caused cerebral infarction. With ketamine, the NSS at 24 and 48 h following head trauma was 7.4 +/- 2.6 and 6.7 +/- 2.6 (mean +/- SEM), respectively, significantly improved compared to the NSS in the untreated group of 12.6 +/- 2.6 and 11.3 +/- 2.6, respectively (p <0.02, Mann-Whitney U test). With ketamine, the volume of hemorrhagic necrosis was 88.0 +/- 23.1 mm, significantly less than that in the untreated group (147.4 +/- 22.4 mm; p <0.05, unpaired t test). The brain tissue specific gravity and water content at 48 h and the rectal temperature at 4 and 48 h after head trauma were not significantly different between treated and untreated groups. It is concluded that in this model of closed cranial impact, ketamine improves neurological outcome and decreases the volume of hemorrhagic necrosis without altering brain edema.     

Evidence against leukotrienes as mediators of brain edema

Leukotrienes are powerful metabolites of arachidonic acid which are known to increase the permeability of peripheral blood vessels. These substances are found in brain tissue in association with cerebral ischemia, and in brain tumors. Therefore, it has been proposed that leukotrienes have a mediator function in brain edema. This hypothesis was subjected to further experimental analysis in this study, in which the authors investigated whether: 1) superfusion of the exposed brain surface with leukotrienes increases the permeability of extraparenchymal blood vessels in vivo; 2) intraparenchymal infusion of leukotrienes induces brain edema; and 3) pharmacological inhibition of leukotriene formation by BW755C, an inhibitor of leukotriene synthesis, reduces formation of brain edema from a standardized traumatic insult. The pial vessels of the parietal cortex of cats were examined by fluorescence microscopy during cerebral superfusion with the leukotrienes C4 (LTC4), D4 (LTD4), or E4 (LTE4) by using an open cranial window preparation. Intravenous Na(+)-fluorescein served as an in vivo blood-brain barrier (BBB) indicator. Superfusion of the pia with leukotrienes (up to 2 microM) did not open the barrier to fluorescein, but was associated with a significant constriction (up to 25%) of arterial and venous vessels. In experiments with slow infusion of leukotriene B4 (LTB4) or LTC4 into the white matter of feline brain, the tissue water content was subsequently determined in serial brain slices using the specific gravity method. Tissue water profiles obtained after a 15-microM infusion of either LTB4 or LTC4 were virtually identical with those of control animals infused with mock cerebrospinal fluid. Thus, neither LTB4 nor LTC4 led to an augmentation of infusion-induced brain edema. In a final series, a cold lesion of the left parietal cortex was induced in rabbits. Twenty-four hours later, swelling of the exposed hemisphere was quantified by gravimetrical comparison of its weight with that of the contralateral nontraumatized hemisphere. Eight animals received BW755C intravenously prior to and after trauma to inhibit formation of leukotrienes. Seven rabbits were infused with an equivalent volume of saline as a control study. The resulting hemispheric swelling was 7.7% +/- 0.6% (mean +/- standard error of the mean) 24 hours later in animals receiving BW755C and 7.8% +/- 1.2% in the control group, indicating that inhibition of leukotrienes was ineffective in preventing formation of vasogenic brain edema. The findings demonstrate that leukotrienes administered to the brain in concentrations occurring under pathological conditions do not open the BBB nor do they induce brain edema.(ABSTRACT TRUNCATED AT 400 WORDS)     

Bradykinin B2 receptor antagonism with LF 18-1505T reduces brain edema and improves neurological outcome after closed head trauma in rats

BACKGROUND: We evaluated the effect of LF 18-1505T, a novel nonpeptide bradykinin type-2 receptor antagonist, on brain edema and neurologic severity score (NSS) after closed head trauma (CHT). METHODS: There were 132 rats anesthetized and assigned for sham or CHT; infusion of saline or LF 18-1505T (0.3, 1, 3, 10, or 30 microg x kg x min); and determination of neurologic outcome (brain water content and NSS) or physiologic variables (blood pressure, glucose concentration, etc.). RESULTS: Post-CHT brain water content was less with LF 18-1505T doses of 3 and 10 microg x kg x min (80.1 +/- 3.8 through 81.6 +/- 2.6%, mean +/- SD) than in the untreated group (84.6 +/- 1.9%, p < 0.01). Post-CHT NSS improved with doses of 3, 10, and 30 microg x kg x min (median, 7; range, 0-12 through median, 10; range, 8-18) as compared with that in the untreated group (median, 17; range, 14-23; p < 0.05). LF 18-1505T with or without CHT did not significantly alter physiologic variables. CONCLUSIONS: LF 18-1505T decreased brain edema and improved neurologic status after CTH in rats without significantly altering physiologic values.     

Autoradiographic analysis of mouse brain kinin B1 and B2 receptors after closed head trauma and ability of Anatibant mesylate to cross the blood-brain barrier

The potent non-peptide B2 receptor (R) antagonist, Anatibant mesylate (Ms) (LF 16-0687 Ms), reduces brain edema and improves neurological function recovery in various focal and diffuse models of traumatic brain injury in rodents. In the present study, alteration of kinin B1 and B2R after closed head trauma (CHT) and in vivo binding properties of Anatibant Ms (3 mg/kg, s.c.) injected 30 min after CHT were studied in mice by autoradiography using the radioligands [125I]HPP-Hoe 140 (B2R), and [125I]HPP-des-Arg10-Hoe 140 (B1R). Whereas B1R is barely detected in most brain regions, B2R is extensively distributed, displaying the highest densities in the hindbrain. CHT was associated with a slight increase of B1R and a decrease of B2R (10-50%) in several brain regions. Anatibant Ms (Ki = 22 pM) displaced the B2R radioligand from its binding sites in several areas of the forebrain, basal ganglia and hindbrain. Displacement was achieved in 1 h and persisted at 4 h post-injection. The inhibition did not exceed 50% of the total specific binding in non-injured mice. After CHT, the displacement by Anatibant Ms was higher and almost complete in the cortex, caudate putamen, thalamus, hippocampus, medial geniculate nucleus, ventral tegmental area, and raphe. Evans blue extravasation in brain tissue at 4 h after CHT was abolished by Anatibant Ms. It appeared that Anatibant Ms penetrated into the brain in sufficient amounts, particularly after disruption of the blood-brain barrier, to account for its B2R-mediated neuro- and vascular protective effects. The diminished binding of B2R after CHT may reflect the occupancy or internalization of B2R following the endogenous production of bradykinin (BK).     

The kallikrein-kinin system as mediator in vasogenic brain edema. Part 3: Inhibition of the kallikrein-kinin system in traumatic brain swelling

Evidence has previously been provided that administration of kinins to the cerebrum causes edema and opening of the blood-brain barrier. It has further been shown that these highly active compounds are formed in the brain under pathophysiological conditions. Their formation was enhanced when cerebral blood flow became compromised by an increase in intracranial pressure. Final evidence, however, was not available as to whether specific inhibition of the kallikrein-kinin (KK) system has a therapeutic function in acute head injury. The authors have demonstrated in rabbits that inhibition of the activating enzyme kallikrein by aprotinin or by aprotinin plus soybean trypsin inhibitor (SBTI), which interfere with plasma and tissue kallikrein, is associated with a decrease in formation of posttraumatic swelling after a standardized cold lesion to the brain. Saline-treated control animals with cerebral cold-induced injury had an increase in hemispheric weight 24 hours later of 13.0% +/- 0.8% (standard error of the mean) in the damaged hemisphere compared to the contralateral nondamaged hemisphere. Administration of aprotinin or aprotinin plus SBTI led to a significant reduction of hemispheric swelling of 10.1% +/- 0.7% or 10.4% +/- 0.7%, respectively. In animals receiving SBTI only, hemispheric swelling evolving from cold injury was not significantly reduced. Therapeutic reduction of brain edema by aprotinin cannot be attributed to a nonspecific effect on the blood pressure, which in the experimental groups remained almost normal as compared to the control animals. Failure of SBTI to influence posttraumatic brain swelling may have resulted from disturbances in intravascular coagulation. Measurements of aprotinin in plasma and tissue demonstrate that the inhibitor doses employed are within an effective therapeutic range. Attenuation of brain edema by specific inhibition of the KK system provides evidence for a mediator role of kinins in vasogenic edema. Clinical trials with inhibitors of the KK system in acute forms of traumatic lesions associated with vasogenic edema appear worthwhile.     

Differential effects of prolonged isoflurane anesthesia on plasma,extracellular, and CSF glutamate,neuronal activity, <Superscript>125</Superscript>I-Mk801 NMDA receptor binding,and brain edema in traumatic brain-injured rats

Summary Background. Volatile anesthetics reduce neuronal excitation and cerebral metabolism but can also increase intracellular water accumulation in normal and injured brains. While attenuation of neuronal excitation and glutamate release are beneficial under pathological conditions, any increase in edema formation should be avoided. In the present study we investigated duration-dependent effects of the commonly used isoflurane/nitrous oxide (N₂O) anesthesia on EEG activity, specific NMDA receptor binding, extracellular, CSF, and plasma glutamate, and cerebral water content in brain-injured rats subjected to short (30 minutes) or prolonged (4 hours) anesthesia.Methods. Before controlled cortical impact injury (CCI), during prolonged (4–8 hours) or short anesthesia (7.5–8 hours after CCI), and before brain removal, changes in neuronal activity were determined by quantitative EEG analysis and glutamate was measured in arterial plasma. Brains were processed to determine acute and persisting changes in cerebral water content and ¹²⁵I-Mk801 NMDA receptor binding at 8 and 32 hours after CCI, i.e., immediately or 24 hours after short or prolonged anesthesia. During prolonged anesthesia glutamate was measured via microdialysis within the cortical contusion. CSF was sampled before brain removal.Findings. Prolonged isoflurane (1.8 vol%) anesthesia significantly increased EEG activity, plasma, cortical extracellular, and CSF glutamate, cortical and hippocampal ¹²⁵I-Mk801 NMDA receptor binding, and cerebral water content in brain-injured rats. These changes were partially reversible within 24 hours after prolonged anesthesia. At 24 hours, CSF glutamate was significantly reduced following long isoflurane anesthesia compared to rats previously subjected to short anesthesia despite an earlier significant increase.Conclusions. The partially reversible increases in EEG activity, ¹²⁵I-Mk801 NMDA receptor binding, cerebral water content, plasma and CSF glutamate appear important for physiological, pathophysiological, and pharmacological studies requiring prolonged anesthesia with isoflurane. Increases in extracellular cortical and plasma glutamate could contribute to acute aggravation of underlying tissue damage.     

Small volume resuscitation with HyperHaes improves pericontusional perfusion and reduces lesion volume following controlled cortical impact injury in rats

The hyperosmolar and hyperoncotic properties of HyperHaes (HHES) might improve impaired posttraumatic cerebral perfusion. Possible beneficial effects on pericontusional perfusion, brain edema, and contusion volume were investigated in rats subjected to controlled cortical impact (CCI). Male Sprague-Dawley rats (n = 60) anesthetized with isoflurane were subjected to a left temporoparietal CCI. Thereafter, rats were randomized to receive HHES (10% hydroxyethylstarch, 7.5% NaCl) or physiological saline solution (4 mL/kg body weight) intravenously. Mean arterial blood pressure (MABP) and intracranial pressure (ICP) were determined before and following CCI, after drug administration and 24 h later. Regional pericontusional cortical perfusion was determined by scanning laser Doppler flowmetry before CCI, and 30 min, 4 and 24 h after injury. At 24 h brain swelling and water content were measured gravimetrically. At 7 days, cortical contusion volume was determined planimetrically. MABP was not influenced by HHES. ICP was significantly decreased immediately after HHES infusion (5.7 +/- 0.4 vs. 7.1 +/- 1.0 mm Hg; p < 0.05). Pericontusional cortical perfusion was significantly decreased by 44% compared to pre-injury levels (p < 0.05). HHES significantly improved cortical perfusion at 4 h after CCI, approaching baseline values (85 +/- 12%). While increased posttraumatic brain edema was not reduced by HHES at 24 h, cortical contusion volume was significantly decreased in the HHES-treated rats at 7 days after CCI (23.4 +/- 3.5 vs. 39.6 +/- 6.2 mm3; p < 0.05). Intravaneous administration of HHES within 15 min after CCI has a neuroprotective potential, as it significantly attenuated impaired pericontusional perfusion and markedly reduced the extent of induced structural damage.     

Contribution of polyamine oxidase to brain injury after trauma.

OBJECT: The possible role of the polyamine interconversion pathway on edema formation, traumatic injury volume, and tissue polyamine levels after traumatic brain injury (TBI) was studied using an inhibitor of the interconversion pathway enzyme, polyamine oxidase. METHODS: Experimental TBI was induced in Sprague-Dawley rats by using a controlled cortical impact device at a velocity of 3 m/second, resulting in a 2-mm deformation. Immediately after TBI was induced, 100 mg/kg of N1,N4-bis(2,3-butadienyl)-1,4-butanediamine 2HCl (MDL 72527) or saline was injected intraperitoneally. Brain water content and tissue polyamine levels were measured at 24 hours after TBI. Traumatic injury volume was evaluated using 2% cresyl violet solution 7 days after TBI occurred. The MDL 72527 treatment significantly reduced brain edema (80.4+/-0.8% compared with 81.2+/-1.2%, p < 0.05) and injury volume (30.1+/-6.6 mm3 compared with 42.7+/-13.3 mm3, p < 0.05) compared with the saline treatment. The TBI caused a significant increase in tissue putrescine levels at the traumatized site (65.5+/-26.5 nmol/g [corrected] in the cortex and 70.9+/-22.4 nmol/g [corrected] in the hippocampus) compared with the nontraumatized site (7+/-2.4 nmol/g [corrected] in the cortex and 11.4+/-6.4 nmol/g [corrected] in the hippocampus). The increase in putrescine levels in both the traumatized and nontraumatized cortex and hippocampus was reduced by a mean of 60% with MDL 72527 treatment. CONCLUSIONS: These results demonstrate, for the first time, that the polyamine interconversion pathway has an important role in the increase of putrescine levels after TBI and that the polyamine oxidase inhibitors, blockers of the interconversion pathway, can be neuroprotective against edema formation and necrotic cavitation after TBI.     

Platelet-activating factor antagonists do not attenuate delayed posttraumatic cerebral edema in rats

Platelet-activating factor (PAF) receptor antagonists reportedly improve early postischemic neurological recovery and cerebral blood flow in selected experimental models. Their effects on posttraumatic cerebral edema have, however, not been examined. In a rat model of right hemispheric percussive cerebral trauma, we examined the effects of two PAF receptor antagonists on posttraumatic edema formation. Two groups of rats received either BN 52021 (n = 14) or WEB 2086 (n = 11), 10 mg/kg i.v. at 15 min posttrauma. Two other groups treated with the BN 52021 (n = 17) and WEB 2086 (n = 10) vehicles served as controls. Hemispheric percent brain water was determined at 24 h. Edema occurred in all groups. Neither PAF receptor antagonist significantly reduced right hemispheric percent brain water (81.08 +/- 0.25 and 81.04 +/- 0.15 in Bn 52021 and WEB 2086-treated rats, respectively, versus 81.31 +/- 0.23 and 81.14 +/- 0.17% brain water in BN 52021 vehicle and WEB 2086 vehicle-treated rats). Mortality was not statistically different between groups. These data do not support a major role for PAF in the development of posttraumatic cerebral edema.