Neurobehavioral protection by the neuronal calcium channel blocker ziconotide in a model of traumatic diffuse brain injury in rats

OBJECT: Abnormal accumulation of intracellular calcium following traumatic brain injury (TBI) is thought to contribute to a cascade of cellular events that lead to neuropathological conditions. Therefore, the possibility that specific calcium channel antagonists might exert neuroprotective effects in TBI has been of interest. The focus of this study was to examine whether Ziconotide produces such neuroprotective effects. METHODS: The authors report that the acceleration-deceleration model of TBI developed by Marmarou, et al., induces a long-lasting deficit of neuromotor and behavioral function. The voltage-sensitive calcium channel blocker Ziconotide (also known as SNX-111 and CI-1009) exerts neuroprotective effects in this model of diffuse brain injury (DBI) in rats. The dose and time of injection of Ziconotide chosen for the present study was based on the authors' previous biochemical studies of mitochondria. Rats were trained in a series of motor and memory tasks, following which they were subjected to DBI using the Marmarou, et al., model. At 3, 5, and 24 hours, all rats were injected with 2 mg/kg Ziconotide for a total cumulative dose of 6 mg/kg Ziconotide. Control brain-injured animals were injected with an equal volume of saline vehicle at each of these time points. The rats were tested for motor and cognitive performance at 1, 3, 7,14, 21, 28, 35, and 42 days postinjury. Saline-treated rats displayed severe motor and cognitive deficits after DBI. Compared with saline-treated control animals, rats treated with Ziconotide displayed better motor performance during inclined plane, beam balance, and beam walk tests; improved memory while in the radial arm maze; and improved learning while in the Morris water maze. CONCLUSIONS: These results demonstrated that the acceleration-deceleration model, which had been developed by Marmarou, et al., induces severe motor and cognitive deficits. We also demonstrated that Ziconotide exhibits substantial neuroprotective activity in this model of TBI. Improvement was observed in both motor and cognitive tasks, even though treatment was not initiated until 3 hours after injury. These findings support the development of neuronal N-type calcium channel antagonists as useful therapeutic agents in the treatment of TBI.     

Post-trauma administration of caffeine plus ethanol reduces contusion volume and improves working memory in rats

It has been demonstrated that ethanol exerts dose-dependent effects, both beneficial and detrimental, on the outcome of traumatic brain injury (TBI). Recently, it has been reported that co-administration of caffeine (10 mg/kg) and a low amount of alcohol (0.65 g/kg; caffeinol) reduces cortical infarct volume up to 80%, and improves motor coordination, following a rodent model of reversible common carotid/middle cerebral artery occlusion. However, the protective effects of caffeinol following other CNS insults, nor its influence on cognitive function, have been examined. Using a controlled cortical impact model of brain injury, the effect of caffeinol administration on TBI-associated motor and cognitive deficits was assessed. When given 15 min following injury, caffeinol reduced cortical tissue loss and improved working memory. However, no influence on motor skills, Morris water maze performance or associative learning and memory was observed. Delayed administration (6 h post-injury) of caffeinol containing a dose of ethanol (1 g/kg) previously demonstrated to improve motor performance eliminated the working memory benefit and cortical protection. These results indicate that early administration of caffeinol may be beneficial in lessening some of the deficits and cortical tissue loss associated with brain trauma.     

Differential effects of the anticonvulsant topiramate on neurobehavioral and histological outcomes following traumatic brain injury in rats

The efficacy of topiramate, a novel therapeutic agent approved for the treatment of seizure disorders, was evaluated in a model of traumatic brain injury (TBI). Adult male rats were anesthetized (sodium pentobarbital, 60 mg/kg, i.p.), subjected to lateral fluid percussion brain injury (n = 60) or sham injury (n = 47) and randomized to receive either topiramate or vehicle at 30 min (30 mg/kg, i.p.), and 8, 20 and 32 h postinjury (30 mg/kg, p.o.). In Study A, memory was evaluated using a Morris water maze at 48 h postinjury, after which brain tissue was evaluated for regional cerebral edema. In Study B, animals were evaluated for motor function at 48 h and 1, 2, 3, and 4 weeks postinjury using a composite neuroscore and the rotating pole test and for learning ability at 4 weeks. Brains were analyzed for hemispheric tissue loss and hippocampal CA3 cell loss. Topiramate had no effect on posttraumatic cerebral edema or histologic damage when compared to vehicle. At 48 h, topiramate treatment improved memory function in sham but not brain-injured animals, while at one month postinjury it impaired learning performance in brain-injured but not sham animals. Topiramate significantly improved composite neuroscores at 4 weeks postinjury and rotating pole performance at 1 and 4 weeks postinjury, suggesting a potentially beneficial effect on motor function following TBI.     

Alteration of Ischemic Reperfusion Injury in the Rat Neocortex by a Potent Antioxidant Mexiletine

Summary.  The mechanisms by which mexiletine exerts its effects in increasing myocardial circulation, and smooth muscle perfusion and alleviating diabetic neuropathic pain have been widely discussed. The purpose of this study was to examine the protective effect of this compound in ischemia/reperfusion-induced cerebral injury following middle cerebral artery occlusion in Spraque-Dawley rats. Blood flow to the left cerebral hemisphere of the animals was interrupted by occluding the left cerebral artery and both carotid arteries simultaneously for 3 hrs. These animals were assigned to one of ten groups and devided into treatment group and pretreatment group; 1) control treatment group (n=8); 2) vehicle treatment group (n=8); 3) lower dose mexiletine (400 μg/kg) treatment group (n=8); 4) medium dose mexiletine (800 μg/kg) treatment group (n=8); 5) high dose mexiletine (2 mg/kg) treatment group (n=8); 6) control pretreatment group (n=8); 7) vehicle pretreatment group (n=8); 8) lower dose mexiletine (400 μg/kg) pretreatment group (n=8); 9) medium dose mexiletine (800 μg/kg) pretreatment group (n=8); and 10) high dose mexiletine (2 mg/kg) pretreatment group (n=8). The volume of cerebral infarction was measured in serial brain sections stained with triphenyltetrazolium chloride (TTC). Tissue infarction volume and tissue edema were estimated for each animal. The volume of cerebral infarction was significantly decreased in rats pretreated with mexiletine, and the ratio of tissue edema was also decreased as the dose of mexiletine increased.  These results demonstrate that mexiletine, an anti-arrhythmic and use-dependent Na⁺ channel blocker, has protective effects in stroke at concentrations sufficient to confer significant protection, as measured by the volume of infarction and brain edema index in a model of focal, neocortical ischemia in Spraque-Dawley rats.     

Reduction of ischemic brain injury in rats with normothermic and hyperthermic conditions

OBJECT: Statins have been used for induction of ischemic tolerance after cerebral ischemia. The authors have previously shown that simvastatin is protective after ischemic cerebral injury in normothermic conditions. In this study they further examined whether treatment with simvastatin can reduce ischemic brain injury in a hyperthermic condition. METHODS: Focal ischemic brain injury was induced by embolizing a preformed clot into the middle cerebral artery in rats. The authors initially examined whether treatment with simvastatin could reduce ischemic brain injury without or with hyperthermia. The infarct volume, edema, and neurological deficits were examined. They then studied whether simvastatin could reduce the perfusion deficits, damage to the blood-brain barrier (BBB), and degeneration of neurons in the ischemic injured brain. RESULTS: Simvastatin significantly reduced the infarct volume in both normothermic and hyperthermic conditions, compared with appropriate controls. Concomitantly, this treatment also significantly reduced neurological deficits and brain edema. Administration of simvastatin significantly decreased perfusion deficits, BBB permeability, and degenerated neurons. CONCLUSIONS: These studies suggest that simvastatin is an effective agent for ischemic brain injury not only in normothermic but also in hyperthermic conditions, which may be through the decrease of BBB permeability, degenerated neurons, and perfusion deficits.     

Estrogen therapy for experimental intracerebral hemorrhage in rats

OBJECT: The aims of this study were to determine the following: whether there are sex differences in intracerebral hemorrhage (ICH) induced brain injury in rats, whether delayed administration of 17beta-estradiol can reduce ICH-induced brain damage, and whether these effects are estrogen receptor (ER)-dependent. METHODS: Male and female Sprague-Dawley rats received an infusion of 100 microl autologous whole blood into the right basal ganglia. Twenty-four hours later the rats were killed. The effects of 17beta-estradiol on ICH-induced brain injury were examined by measuring brain edema and neurological deficits. Both ER-alpha and hemeoxygenase (HO)-1 were investigated through Western blot and immunohistochemical analysis. Brain edema was significantly less severe in female compared with that in male rats. The ER antagonist ICI 182,780 exacerbated ICH-induced brain edema in female but not in male rats, indicating that ER-alpha activation during ICH is protective in female rats. Administration of exogenous 17beta-estradiol in male, but not in female, rats significantly attenuated brain edema, neurological deficits, and ICH-induced changes in HO-1 when given 2 hours after hemorrhage. The effects of exogenous 17beta-estradiol occurred through an ER-independent mechanism. CONCLUSIONS: Results in this study indicate that 17beta-estradiol could be a potential therapeutic agent for ICH.     

Effects of crystalloid-colloid solutions on traumatic brain injury

The purpose of this study was to compare the effects of crystalloid and crystalloid-colloid solutions administered at different times after isolated traumatic brain injury. Male Sprague-Dawley rats were randomized to receive one of three intravenous treatments (4 mL/kg body weight) at 10 min or 6 h after moderate traumatic brain injury. Treatments included hypertonic saline, hypertonic albumin, and normal albumin. Moderate injuries were produced using the controlled cortical impact injury model set at 2.0 mm, 4.0 m/sec, and 130 msec. Tissue damage and cerebral edema were measured to evaluate the effect of treatments for traumatic brain injury. Blood brain barrier permeability was assessed at different time points after injury to identify a mechanism for treatment effectiveness. Injury volume was the smallest for animals treated with hypertonic albumin at 6 h after injury compared to all other treatments and administration times. Ipsilateral brain water content was significantly attenuated with immediate normal saline-albumin treatment. The presence of colloid in the infusion solutions was associated with an improvement in tissue damage and edema following isolated head injury while hypertonic saline alone, when given immediately after injury, worsened tissue damage and edema. When hypertonic saline was administered at 6 h after injury, tissue damage and edema were not worsened. In conclusion, the presence of colloid in solutions used to treat traumatic brain injury and the timing of treatment have a significant impact on tissue damage and edema.     

Attenuation of working memory and spatial acquisition deficits after a delayed and chronic bromocriptine treatment regimen in rats subjected to traumatic brain injury by controlled cortical impact

Cognitive impairments are pervasive and persistent sequelae of human traumatic brain injury (TBI). In vivo models of TBI, such as the controlled cortical impact (CCI) and fluid percussion (FP), are utilized extensively to produce deficits reminiscent of those seen clinically with the hope that empirical study will lead to viable therapeutic interventions. Both CCI and FP produce spatial learning acquisition deficits, but only the latter has been reported to impair working memory in rats tested in the Morris water maze (MWM). We hypothesized that a CCI injury would impair working memory similarly to that produced by FP, and that delayed and chronic treatment with the D2 receptor agonist bromocriptine would attenuate both working memory and spatial learning acquisition deficits. To test these hypotheses, isoflurane-anesthetized adult male rats received either a CCI (2.7 mm deformation, 4 m/sec) or sham injury, and 24 h later were administered bromocriptine (5 mg/kg, i.p.) or vehicle, with continued daily injections until all behavioral assessments were completed. Motor function was assessed on beam balance and beam walking tasks on postoperative days 1-5 and cognitive function was evaluated in the MWM on days 11-15 for working memory (experiment 1) and on days 14-18 for spatial learning acquisition (experiment 2). Histological examination (hippocampal CA1 and CA3 cell loss/survival and cortical lesion volume) was conducted 4 weeks after surgery. All injured groups exhibited initial impairments in motor function, working memory, and spatial learning acquisition. Bromocriptine did not affect motor function, but did ameliorate working memory and significantly attenuated spatial acquisition deficits relative to the injured vehicle-treated controls. Additionally, the injured bromocriptine-treated group exhibited significantly more morphologically intact CA3 neurons than the injured vehicle-treated group (55.60 +/- 3.10% vs. 38.34 +/- 7.78% [p = 0.03]). No significant differences were observed among TBI groups in CA1 cell survival (bromocriptine, 40.26 +/- 4.74% vs. vehicle, 29.13 +/- 6.63% [p = 0.14]) or cortical lesion volume (bromocriptine, 17.78 +/- 0.62 mm3 vs. vehicle, 19.01 +/- 1.49 mm3 [p > 0.05]). These data reveal that CCI produces working memory deficits in rats that are similar to those observed following FP, and that the delayed and chronic bromocriptine treatment regimen conferred cognitive and neural protection after TBI.     

Acute effects of a selective cannabinoid-2 receptor agonist on neuroinflammation in a model of traumatic brain injury

Proposed therapeutic strategies for attenuating secondary traumatic brain injury (TBI) include modulation of acute neuroimmune responses. The goal of this study was to examine the acute effects of cannabinoid-2 receptor (CB(2)R) modulation on behavioral deficits, cerebral edema, perivascular substance P, and macrophage/microglial activation in a murine model of TBI. Thirty male C57BL/6 mice underwent sham surgery, or cortical contusion impact injury (CCI). CCI mice received vehicle or the CB(2)R agonist 0-1966 at 1 and 24 h after injury. Performance on the rotarod, forelimb cylinder, and open-field tests were evaluated before and at 48 h after sham or CCI surgery. Cerebral edema was evaluated using the wet-dry weight technique. Immunohistochemical analysis was used to examine changes in substance P and macrophage/microglia-specific Iba1 protein immunoreactivity. Locomotor performance and exploratory behavior were significantly improved in mice receiving 0-1966 (CB(2)R agonist) compared to vehicle-treated mice. Significant reductions were found for cerebral edema, number of perivascular areas of substance P immunoreactivity, and number of activated macrophages/microglial cells in the injured brains of 0-1966-treated mice compared to vehicle-treated mice. The findings show that the effects of the CB(2)R agonist 0-1966 on edema, substance P immunoreactivity, and macrophage/microglial activation, were associated with recovery of acute motor and exploratory deficits. This study provides evidence of acute neuroprotective effects derived from selective CB(2)R activation that may represent an avenue for further development of novel therapeutic agents in the treatment of TBI.     

Effects of the N-methyl-D-aspartate receptor blocker MK-801 on neurologic function after experimental brain injury

Pharmacologic inhibition of excitatory amino acid (EAA) neurotransmission attenuates cell death in models of global and focal ischemia and hypoglycemia and improves neurologic outcome after experimental traumatic spinal cord injury. The present study examined the effects of the noncompetitive N-methyl-D-aspartate (NMDA) receptor blocker MK-801 on cardiovascular and neurologic function after experimental fluid-percussion (FP) brain injury in the rat. Animals received either an intravenous bolus of MK-801 (1 mg/kg) or saline (equal volume) 15 min prior to FP brain injury or 15 min following FP brain injury. MK-801 pretreatment significantly improved postinjury cardiovascular variables and attenuated postinjury neurologic dysfunction. Postinjury treatment with MK-801 also significantly improved cardiovascular variables, but had little effect on postinjury neurologic scores. These results suggest that EAA neurotransmitters may be involved in the pathophysiological sequelae of traumatic brain injury and that noncompetitive blockade of the NMDA receptor prior to brain injury may reduce EAA-induced damage and limit neurologic dysfunction.     

七氟醚麻醉对局灶性脑缺血再灌注大鼠脑组织水通道蛋白9表达的影响

目的 评价七氟醚麻醉对局灶性脑缺血再灌注大鼠脑组织水通道蛋白9( AQP-9)表达的影响.方法 成年雄性SD大鼠75只,体重230～270 g,采用随机数字表法,将其随机分为3组(n=25):假手术组(S组)、缺血再灌注组(UR组)和七氟醚麻醉组(SE组).S组和I/R组静脉注射芬太尼10μg/kg后静脉输注芬太尼25μg·kg-1·h-1,吸入65％N2O和35％O2;SE组吸入2.0％七氟醚和35％ O2.I/R组和SE组采用线栓法制备大鼠局灶性脑缺血再灌注模型,缺血2h后恢复灌注.分别于再灌注6h、1、2、3和5d时测定神经功能缺陷评分和脑组织AQP-9表达,计算脑肿胀率.结果 与S组比较,I/R组和SE组再灌注6h、1、2、3和5d时神经功能缺陷评分升高,再灌注1、2、3d时脑肿胀率升高,再灌注1、2、3和5d时脑组织AQP-9表达上调(P＜0.05);与I/R组比较,SE组再灌注2和3d时神经功能缺陷评分下降,脑肿胀率降低,再灌注2、3和5d时脑组织AQP-9表达上调(P＜0.05).结论 七氟醚麻醉减轻大鼠局灶性脑缺血再灌注损伤的机制与上调脑组织AQP-9的表达有关.     

Neuroprotective effects of citicoline on brain edema and blood-brain barrier breakdown after traumatic brain injury

OBJECT: Cytidine 5'-diphosphocholine (CDPC), or citicoline, is a naturally occurring endogenous compound that has been reported to provide neuroprotective effects after experimental cerebral ischemia. However, in no study has such protection been shown after traumatic brain injury (TBI). In this study the authors examined the effect of CDPC on secondary injury factors, brain edema and blood-brain barrier (BBB) breakdown, after TBI. METHODS: After anesthesia had been induced in Sprague-Dawley rats by using 1.5% halothane, an experimental TBI was created using a controlled cortical impact (CCI) device with a velocity of 3 m/second, resulting in a 2-mm deformation. Four sham-operated control animals used for brain edema and BBB breakdown studies underwent the same surgical procedure, but received no injury. Brain edema was evaluated using the wet-dry method 24 hours postinjury, and BBB breakdown was evaluated by measuring Evans blue dye (EBD) extravasation with fluorescein 6 hours after TBI. The animals received intraperitoneal injections of CDPC (50, 100, or 400 mg/kg two times after TBI [eight-10 animals in each group]) or saline (eight animals) after TBI. Traumatic brain injury induced an increase in the percentage of water content and in EBD extravasation in the injured cortex and the ipsilateral hippocampus. No significant benefit from CDPC treatment was observed at a dose of 50 mg/kg. Cytidine 5'-diphosphocholine at a dose of 100 mg/kg attenuated EBD extravasation in both regions, although it reduced brain edema only in the injured cortex. In both regions, 400 mg/ kg of CDPC significantly decreased brain edema and BBB breakdown. CONCLUSIONS: This is the first report in which dose-dependent neuroprotective effects of CDPC have been demonstrated in the injured cortex as well as in the hippocampus, a brain region known to be vulnerable to injury, after experimental TBI. The results of this study suggest that CDPC is an effective neuroprotective agent on secondary injuries that appear following TBI.     

Neuroprotective effect of tadalafil,a PDE-5 inhibitor,and its modulation by L-NAME in mouse model of ischemia-reperfusion injury

Background

The present study investigates the neuroprotective effect of tadalafil, a selective phosphodiesterase-5 inhibitor, in a mouse model of ischemia-reperfusion injury.

Materials and methods

Bilateral carotid artery occlusion for 12 min followed by reperfusion for 24 h was employed to produce ischemia-reperfusion-induced cerebral injury in male Swiss mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using Morris water maze test. Degree of motor incoordination was evaluated using inclined beam walk test, rota-rod test, and lateral push test. Brain nitrite/nitrate, brain acetylcholinesterase activity, brain thiobarbituric acid reactive species, and glutathione levels were also estimated.

Results

Bilateral carotid artery occlusion, followed by reperfusion, produced a significant rise in cerebral infarct size, brain nitrite/nitrate levels, acetylcholinesterase activity, and thiobarbituric acid reactive species level along with a fall in glutathione. A significant impairment of memory and motor coordination was also noted. Pretreatment of tadalafil significantly attenuated the above effects of ischemia-reperfusion injury. Tadalafil-induced neuroprotective effects were significantly attenuated by administration of L-NAME, a nonselective nitric oxide synthase inhibitor.

Conclusions

Results indicate that tadalafil exerts neuroprotective effects, probably through nitric oxide–dependent pathways. Therefore, phosphodiesterase-5 can be explored as an important target to contain ischemia-reperfusion injury.     

Protective Effects of Memantine Against Ischemia-Reperfusion Injury in Spontaneously Hypertensive Rats

Summary  Memantine, an uncompetitive NMDA open-channel blocker, has been shown to be effective in preventing neuronal damage after permanent focal cerebral ischemia. Reperfusion after a long period of ischemia may aggravate the progression of neuronal damage. Those drugs that show protective effects after permanent cerebral ischemia, therefore, might fail to do so against ischemia-reperfusion injury. In this study we evaluated the effects of memantine on brain edema formation and ischemic injury volume after transient cerebral ischemia. Male Spontaneously Hypertensive Rats (SHR) weighing 250–300 g were anesthetized with halothane and subjected to 1 hour of temporary middle cerebral artery occlusion by an intraluminal suture. 20 mg/kg of memantine or saline were injected intraperitoneally 5 min. after the induction of ischemia. Physiological parameters and regional cerebral blood flow were monitored during the surgical procedure. Brain water content and ischemic injury volume were measured with the wet dry method and 2,3,5-triphenyl tetrazolium chloride monohydrate (TTC) staining, respectively, at 24 hours after occlusion. There were no statistically significant differences between the groups regarding physiological parameters during the procedure. Memantine treatment (n=9) reduced the brain water content significantly in the cortex compared to saline treatment (n=8; 83.1±0.7% vs. 84.5±1.5%, respectively, p<0.05). The total volume of ischemic brain injury was 300±49 mm³ in the animals treated with saline (n=13). Treatment with 20 mg/kg memantine (n=14) reduced the ischemic injury volume to 233±61 mm³ (P<0.01). These results demonstrate that the harmful effects of recirculation after a period of ischemia can be attenuated by the treatment of memantine, perhaps by its action at the NMDA receptors.     

Comparison of behavioral deficits and acute neuronal degeneration in rat lateral fluid percussion and weight-drop brain injury models

The behavioral and histological effects of the lateral fluid percussion (LFP) brain injury model were compared with the weight drop impact-acceleration model with 10 min of secondary hypoxia (WDIA + H). LFP injury resulted in significant motor deficits on the beam walk and inclined plane, and memory deficits on the radial arm maze and Morris water maze. Motor deficits following LFP remained throughout 6 weeks of behavioral testing. WDIA + H injury produced significant motor deficits on the beam walk and inclined plane immediately following injury, but these effects were transient and recovered by 14 days post-injury. In contrast to the LFP injury, the WDIA + H injured animals showed no memory deficits on the radial arm maze and Morris water maze. In order to determine if the differences in behavioral outcome between models were due to differences in injury mechanism or injury severity, 10 LFP-injured animals were matched with 10 WDIA-injured animals based on injury severity (i.e., time to regain righting reflex after brain injury). The LFP-matched injury group showed greater impairment than the WDIA + H matched injury group on the radial arm maze and Morris water maze. Histological examination of LFP-injured brains with Fluoro-Jade staining 24 h, 48 h, and 7 days post-injury revealed degenerating neurons in the cortex, thalamus, hippocampus, caudate-putamen, brainstem, and cerebellum, with degenerating fibers tracts in the corpus callosum and other major tracts throughout the brain. Fluoro-Jade staining following WDIA+H injury revealed damage to fibers in the optic tract, lateral olfactory tract, corpus callosum, anterior commissure, caudate-putamen, brain stem, and cerebellum. While both models produce reliable and characteristic behavioral and neuronal pathologies, their differences are important to consider when choosing a brain injury model.     

Attenuation of brain edema, blood-brain barrier breakdown, and injury volume by ifenprodil, a polyamine-site N-methyl-D-aspartate receptor antagonist, after experimental traumatic brain injury in rats

OBJECTIVE: Traumatic brain injury (TBI) has been shown to induce a significant change in polyamine metabolism. Polyamines and polyamine-dependent calcium influx play an important role in mediating the effects of excitotoxic amino acids at the N-methyl-D-aspartate (NMDA) receptor site. We studied the effects of ifenprodil, known as a noncompetitive inhibitor of polyamine sites at the NMDA receptor, on brain edema formation, blood-brain barrier breakdown, and volume of injury after TBI. METHODS: Experimental TBI was induced in Sprague-Dawley rats by a controlled cortical impact device, functioning at a velocity of 3 m/s to produce a 2-mm deformation. Ifenprodil or saline (10 mg/kg) was injected intraperitoneally immediately after the cortical impact injury and then every 90 minutes until 6 hours after TBI. Blood-brain barrier breakdown was evaluated quantitatively 6 hours after injury by fluorometric assay of Evans blue extravasation. Brain water content, an indicator of brain edema, was measured with the wet-dry method 24 hours after TBI. Injury volume was quantitated from the brain slices stained with 2% cresyl violet solution 7 days after TBI. RESULTS: Blood-brain barrier breakdown was significantly lower in the traumatic cortex of the ifenprodil-treated group than in the saline-treated group (84.4 +/- 26.8 microg/g versus 161.8 +/- 27 microg/g, respectively, P < 0.05). Brain edema was significantly reduced in the cortex of the ifenprodil-treated group relative to that in the saline-treated group (80.9 +/- 0.5% versus 82.4 +/- 0.6% respectively, P < 0.05). Ifenprodil treatment reduced injury volume significantly (14.9 +/- 8.1 mm3 versus 24.4 +/- 6.7 mm3, P < 0.05). CONCLUSION: The polyamine-site NMDA receptor antagonist ifenprodil affords significant neuroprotection in a controlled cortical impact brain injury model and may hold promise for the discovery and treatment of the mechanism of delayed neurological deficits after TBI.     

酸敏感离子通道在大鼠全脑缺血再灌注损伤中的作用

目的 探讨酸敏感离子通道(ASICs)在大鼠全脑缺血再灌注损伤中的作用.方法 雄性SD大鼠48只,体重250～310 g,采用随机数字表法,将大鼠随机分为4组(n=12):假手术组(S组)、缺血再灌注组(I/R组)、生理盐水组(NS组)和ASICs阻断剂组(A组).I/R组、NS组和A组采用阻断双侧颈总动脉和基底动脉10 min的方法制备全脑缺血再灌注模型,NS组和A组于再灌注前即刻 分别静脉注射生理盐水6 ml/kg和ASICs阻断剂阿米洛利0.3 mg/kg.各组取6只大鼠,分别于缺血前(基础状态)、缺血即刻及再灌注20 min期间每隔10 min收集一次海马CA1区微透析液,测定微透析液中乳酸浓度.再灌注8 h时各组取另外6只大鼠,进行方格爬行实验和斜板实验,以评价神经行为学;然后取脑组织,计算脑含水量,并在光镜及电镜下观察大脑皮质的病理学结果.结果 与S组比较,I/R组和NS组微透析液中乳酸浓度和脑含水量升高,发生神经行为学障碍(P＜0.05);与I/R组比较,A组微透析液中乳酸浓度和脑含水量降低,神经行为学改善(P＜0.05),NS组上述指标差异无统计学意义(P＞0.05).A组脑组织损伤程度轻于I/R组.结论 ASICs参与了大鼠全脑缺血再灌注损伤的发生.

Abstract：

Objective To investigate the role of acid-sensing ion channels (ASICs) in global cerebral ischemia-reperfusion (I/R) injury in rats. Methods Forty-eight adult male Sprague-Dawley rats weighing 250-310 g were randomly divided into 4 groups ( n = 12 each): sham operation group (group S); global cerebral I/R group (group I/R); normal saline group (group NS) and specific ASIC blocker amiloride group (group A). Global cerebral I/R was produced by occlusion of 3 vessels ( 10 min occlusion of the bilateral common carotid arteries and basilar artery) followed by reperfusion. In group NS and A, NS 6 ml/kg and amiloride 0.6 mg/kg were injected through femoral vein immediately before reperfusion respectively. Six rats in each group were selected, the dialysate in CA1 area was collected before ischemia (baseline), immediately after ischemia and during 20 min reperfusion (once every 10 min) for determination of lactate concentrations. The left 6 rats in each group were elected at 8 h of reperfusion and the open field test and inclined plane test were peeformed to assess neurological behavior.The rats were then sacrificed and brain tissues taken for microscopic examination and brain water content was calculated. Results Compared with group S, the concentration of lactate in the dialysate and brain water content were significantly increased and neurological deficits developed in group I/R and NS (P ＜ 0.05). Compared with group I/R, the concentration of lactate in the dialysate and brain water content were significantly decreased and neurological deficits were improved in group A ( P ＜ 0.05 ), but no significant change in the parameters mentioned above was found in group NS ( P ＞ 0.05). Microscopic examination showed that the damage to the brain tissues was attenuated in group A compared with group I/R. Conclusion ASICs are involved in the development of global cerebral I/R injury in rats.     

Effects of an N-type calcium channel antagonist (SNX 111; Ziconotide) on calcium-45 accumulation following fluid-percussion injury.

Accumulation of calcium following experimental traumatic brain injury (TBI) has been demonstrated to be a prominent pathophysiological component that can compromise mitochondrial functioning and threaten cell survival. The omega-conopeptide SNX-111, also known as Ziconotide, is a potent antagonist of the voltage-gated N-type calcium channel and has demonstrated significant neuroprotective effects against ischemia-induced neuronal injury. To determine whether this compound would be effective in reducing calcium accumulation associated with TBI, SNX-111 was administered intravenously to rats 1 hour following a moderate (2.2 to 2.75 atm) lateral fluid-percussion injury (or sham) at doses of 1 (n = 30), 3 (n = 31), or 5 (n = 30) mg/kg; another group received 0.9% saline solution (n = 35). Brains were processed for calcium 45 (45Ca) autoradiography at 6, 12, 24, 48, and 96 hours following insult. Optical density measurements of 20 cortical and subcortical regions were analyzed. Injured animals administered saline solution exhibited a significant increase in 45Ca uptake within 12 regions ipsilateral to the site of injury. The most prominent increases were evident throughout the ipsilateral cerebral cortex. SNX-111 reduced the injury-induced calcium accumulation within the ipsilateral cortex in a dose-response fashion when measured at 6, 12, and 48 hours after insult. These drug-induced reductions in calcium accumulation were as high as 75% in the ipsilateral cerebral cortex, and up to 50% in other ipsilateral regions (including thalamus and hippocampus). Consequently, the results suggest that posttraumatic blocking of the voltage-gated N-type calcium channel after injury reduces prolonged, trauma-induced calcium accumulation.     

Sphingosine 1-Phosphate Inhibits Ischemia Reperfusion Injury Following Experimental Lung Transplantation

Ischemia reperfusion (I/R) injury following lung transplantation is exacerbated by the destruction of the endothelial cell barrier leading to pulmonary edema and dysregulated activated lymphocyte migration. Sphingosine 1-phosphate (S1P), a G-coupled protein receptor (GPCR) agonist, has been previously shown to promote endothelial cell tight junction formation and prevent monocyte chemotaxis. We asked if S1P treatment could improve pulmonary function and attenuate I/R injury following syngeneic rat lung transplantation. In comparison to vehicle-treated recipients, S1P administered before reperfusion significantly improved recipient oxygenation following transplantation. Improved graft function was associated with reduced inflammatory signaling pathway activation along with attenuated intragraft levels of MIP-2, TNF-alpha and IL-1beta. Moreover, S1P-treated recipients had significantly less apoptotic endothelial cells, pulmonary edema and graft accumulation of neutrophils than did vehicle-treated recipients. Thus our data show that S1P improves lung tissue homeostasis following reperfusion by enhancing endothelial barrier function and blunting monocytic graft infiltration and inflammation.     

Traumatic brain injury reduces hippocampal alpha7 nicotinic cholinergic receptor binding

Changes in the expression of central nervous system (CNS) neurotransmitter receptors may contribute to behavioral and physiological deficits that occur following traumatic brain injury (TBI). Studies investigating the neurochemical basis for the protracted cognitive dysfunction that follows TBI have focused in part on cholinergic mechanisms. The present study compared the effects of mild and moderate cortical contusion injury (CCI) on the density of cholinergic receptor subtypes, NMDA-type glutamate receptors, and calcium channel expression. Quantitative autoradiography was used to determine the effects of CCI on receptor expression, 48 h following injury. The most robust and consistent change in receptor binding was in the density of alpha7 nicotinic receptors as determined by alpha-[125I]-bungarotoxin (BTX) binding. Bilateral deficits in BTX binding were present following both mild and moderate levels of injury. In contrast, changes in the density of alpha3/alpha4 nAChr's, muscarinic AChr's, NMDA-type glutamate receptors, and L-type calcium channel expression were more regionally restricted and lower in magnitude, as compared to changes in BTX binding. The high calcium permeability of the alpha7 nAChr may be related to the extensive decrease in BTX binding that occurs following TBI.