头部贴敷式亚低温对新生鼠缺氧缺血性脑损伤脑组织中线粒体能量代谢的影响

目的研究头部贴敷式亚低温状态下,新生鼠缺氧缺血性脑损伤时脑组织内能量代谢(ATP、ADP和AMP)的变化,探讨亚低温对缺氧缺血性脑组织的保护机制。方法将88只Wistar新生鼠随机分为4组,分别为假手术常温对照组(CN)、假手术亚低温对照组(CH)、HIBD模型常温恢复组(IN)、HIBD模型亚低温治疗组(IH),每组21只,组内动物再随机分配分为3小组,分别给予常温或亚低温干预,干预持续时间分别为2、6、12h,每个时间点7只动物。结果亚低温治疗组(IH)脑组织中线粒体内ATP、ADP和AMP含量与常温对照组(IN)相比具有差异性(P<0.05)。结论头部贴敷式亚低温可保护脑组织,改善线粒体能量代谢。     

米诺环素对缺氧缺血脑损伤未成熟新生大鼠TLR4、NF—κBp65和TNF—α表达的影响

目的观察米诺环素（Minocycline,MN）对缺氧缺血脑损伤（hypoxic-ischemic brain damage,HIBD）未成熟新生大鼠Toll样受体4（Toll-1ike receptor4,TLR4）、核因子-κB（nuclear factor-kappa B,NF—κB）p65和TNF．仪表达的影响,探索米诺环素脑保护作用机制。方法将160只生后2d（P2）Sprague—Dawley（SD）新生大鼠随机分成正常对照组、假手术组、HIBD组、HIBD加MN组。通过结扎左侧颈总动脉及8％氮氧混合气缺氧4h,制备未成熟新生大鼠缺氧缺血性脑损伤模型。HIBD加MN组大鼠缺氧后予腹腔注射1次MN45mg／kg,HIBD组予腹腔注射等剂量的无菌PBS（pH7．4）。HI后24h、48h、72h取材,Westernblotting检测TLR4、NF．KBp65和TNF—Ot蛋白表达,HI后72h、4周行脑组织HE染色及病理评分,HI后4周行行为学检测。结果HI后72h、4周HIBD加MN组脑组织病理损伤较HIBD组减轻,HIBD加MN组半定量病理评分低于HIBD组,差异有统计学意义（P〈0．05）。Western blotting显示HI后24、48和72hHIBD加MN组TLR4、NF—KBp65和TNF-α的表达低于HIBD组,较正常组及假手术组升高。HI后4周,在悬吊试验及斜坡试验中,HIBD加MN组与正常组、假手术组差异无统计学意义（Jp〉0．05）。旷场试验中,HIBD加MN组与正常组、假手术组对比,差异有统计学意义（P〈0．05）;与HIBD组比较,P=0．375,差异无统计学意义（P〉O．05）。圆筒实验中HIBD加MN组左侧上肢触壁百分比较HIBD组降低（P〈0．05）,与正常组、假手术组差异无统计学意义（P〉0．05）;右侧触壁百分比的比较中,HIBD加MN组与正常组、假手术组、HIBD组差异无统计学意义（P〉0．05）。结论米诺环素对缺氧缺血脑损伤近期及远期具有良好的保护作用,其对缺氧缺血脑损伤的保护作用机制可能与抑制TLR4．NF—κBp65-TNF-α信号途径的激活有关。     

缺氧缺血脑损伤大鼠脑组织Cofilin 1与ERK1/2蛋白表达与磷酸化的分析

目的探索新生大鼠缺氧缺血脑损伤模型脑组织Cofilin1与ERK1/2蛋白表达与磷酸化及其在脑组织中分布的规律。方法新生7日龄SD大鼠,手术结扎左侧颈总动脉并经低氧处理造成缺氧缺血脑损伤(HIBD)模型,以假手术组为对照,应用western Blot和免疫组化方法检测损伤后一定时间段(0h～48h)损伤侧脑组织Cofilin1与磷酸化cofilin1(p-Cofilin1)及Erk1/2和磷酸化ERK1/2(p-ERK1/2)的表达变化,同时检测其在损伤大鼠脑组织和细胞中的表达和分布。结果 Western blot检测显示,HIBD新生SD大鼠脑组织中Cofilin1在HI后的表达与对照组相比也未见明显改变,但磷酸化Cofilin1在HI后1h～12h之间降低,24h后恢复正常;ERK1/2蛋白在不同时点的表达与对照组相比未见明显差异,但可见磷酸化ERK1/2(p-ERK1/2)在缺氧缺血处理(HI)后0h略低于正常,而在1-2h内迅速升高并高于正常对照和假手术,在2h后又逐渐降低。免疫组化结果显示Cofilin1与p-cofilin1在损伤大鼠脑中主要分布于海马和大脑皮质,尤其p-Cofilin表达分布以海马的颗粒细胞为主,并且在HI后7d-14d表达明显增强,在21d则明显降低。结论 Cofilin和ERK的磷酸化修饰与缺氧缺血脑损伤的发生和发展过程有较密切的关系,且cofilin1和p-cofilin1在大脑海马区的定位分布,提示其可能与大脑的学习记忆功能的损伤与修复有一定的关系。     

亚低温对缺氧缺血性脑病大鼠脑内一氧化氮代谢的影响

目的　探讨亚低温对缺氧缺血性脑病大鼠脑内一氧化氮 (NO)代谢的影响。方法　制备新生大鼠缺氧缺血性脑病 (HIE)模型 ,采用 34℃亚低温干预 4 8h ,监测大鼠脑组织内NO含量及一氧化氮合酶 (NOS)的活性。结果　HIE 4 8h后NO含量及NOS的活性明显升高 ,与正常对照组相比有显著差异 (P <0 .0 1) ,亚低温干预组NO含量及NOS的活性无明显升高 ,与HIE组相比有显著差异 (P <0 .0 1)。结论　亚低温可通过抑制NOS活性 ,减少NO的生成 ,防止NO大量生成所致的神经毒性 ,从而对缺氧缺血性脑损伤有保护作用。     

脑缺氧缺血后新生大鼠海马CA1区NMDAR的表达

目的 :研究新生大鼠缺氧缺血性脑损伤 (HIBD)后 ,海马CA1区N甲基D天门冬氨酸受体 (NMDAR)及NMDARmRNA表达的变化。方法 :建立HIBD模型 ,用免疫组化及原位杂交方法 ,检测正常对照 (NORM)组和缺氧缺血 (HI)后不同时间点 ,NMDA受体I型亚单位 (NR1)表达的阳性细胞及NR1mRNA表达的阳性细胞。结果 :HI后 2h时NR1、NR1mR NA的表达稍下降 ,2 4h开始上升 ,72h达高峰 ,与正常对照组相比较有显著意义 (P <0 .0 5 )。结论 :正常新生大鼠海马CA1区有NR1及NR1mRNA的表达 ,HI后NR1及NR1mRNA的表达上调     

CEPO调控新生大鼠缺氧缺血性脑损伤Bcl-2、Bax基因表达的研究

目的 观察新生大鼠缺氧缺血性脑损伤（HIBD）脑组织Bcl-2、Bax基因表达变化及氨基甲酰化促红细胞生成素（CEPO）干预对其表达的影响,探讨CEPO发挥脑保护作用的可能机制.方法 将新生7日龄SD大鼠建立HIBD模型,利用RT-PCR检测缺氧缺血和CEPO干预后2h、12h、24 h、48 h、72 h凋亡基因Bcl-2、Bax的mRNA表达的改变.结果 与假手术组相比,缺氧缺组在2h、12h、24 h、48 h、72 h脑组织中Bcl-2、Bax的表达均增加（P＜0.05）,与缺氧缺血组相比,CEPO干预组在不同时间点Bcl-2表达增加（P＜0.05）,Bax表达下降（P＜0.05）.结论 在新生大鼠HIBD中Bcl-2、Bax mRNA的表达发生改变,调控二者的表达水平可能是CEPO发挥脑保护的作用机制之一.     

缺氧缺血性脑损伤新生大鼠海马区脑红蛋白、凋亡相关蛋白Bcl-2、Bax的表达及其相关性

目的:探讨新生大鼠缺氧缺血性脑损伤(HIBD)后海马CA1区脑红蛋白(Ngb)及凋亡相关蛋白Bcl-2、Bax的变化规律及其相关性。方法:选用60只新生7日龄Wistar大鼠,随机分为三组:sham组(n=6),正常对照组(n=6)和HIBD组(n=48)。HIBD组新生大鼠建立HIBD模型,分别于HIBD后3h、6h、12h、24h、48h、72h、7d、14d取材,应用免疫组织化学染色方法检测各组海马CA1区Ngb及Bcl-2、Bax的表达变化情况。结果:(1)与sham组相比,HIBD组Ngb阳性细胞数于缺氧缺血后3h开始下降,但差异无统计学意义;6h、12h、24h呈逐渐下降趋势,阳性细胞数量已明显低于sham组;到48h时达最低水平;14d时Ngb阳性细胞数量基本恢复至sham组水平。(2)与sham组相比,HIBD组于缺氧缺血3hBcl-2阳性表达细胞开始显著增多,于12h达到高峰,24h时开始逐渐下降,14d时略高于sham组表达,但差异无统计学意义。(3)与sham组相比,HIBD组Bax蛋白免疫反应阳性细胞数目于缺氧缺血后3h时开始增加,12h时明显增多,于48h达高峰,此后逐渐下降,7d时阳性细胞数基本恢复至sham组水平,14d时未见Bax蛋白的阳性表达。(4)新生大鼠海马CA1区内,Ngb阳性细胞数与Bcl-2阳性细胞数无相关;与凋亡相关蛋白Bax阳性细胞数呈负相关(r=-0.697,P0.01)。结论:Bcl-2与Bax基因参与了HIBD后神经细胞凋亡的发生;Ngb可能通过抑制促凋亡蛋白Bax的表达,从而减少神经细胞的凋亡,发挥其神经保护作用。     

亚低温对细胞凋亡及凋亡相关基因表达影响的实验研究

目的　研究亚低温对新生鼠缺氧缺血性脑损伤细胞凋亡及凋亡相关基因表达的影响。方法　7日龄大鼠行左侧颈总动脉结扎后吸入 8%氧气 2h,制成缺氧缺血性脑损伤模型。动物随机分成三组 :假手术组 (C组 ) ,缺氧缺血正常温度组 (HI组 ) ,缺氧缺血后 30min亚低温治疗组。应用原位缺口末端标记 (TUNEL)检测凋亡细胞 ,用免疫组化SABC法检测表达bax基因阳性细胞数。结果　 30min后给予亚低温组凋亡细胞及表达bax基因细胞数明显少于HI组 ,差异有显著意义 (P <0 0 1)。结论　亚低温可以通过抑制细胞凋亡 ,抑制凋亡相关基因的表达等机制发挥对缺氧缺血性脑损伤的保护作用。     

脑缺血再灌注大鼠脑线粒体NO的生成及NOS活性的改变

目的和方法:在局部脑缺血再灌注大鼠模型上,于单纯缺血2 h及再灌30 min、2 h、4 h,分离脑线粒体,检测其内NO的生成以及NO合酶(NOS)活性的变化。结果:脑缺血时线粒体呼吸控制率(RCR)显著下降,再灌4 h稍有恢复。与此相对应,脑线粒体NO生成显著增加,再灌后随时间逐渐减少,4 h接近正常对照水平;脑缺血显著增加了脑线粒体总NOS活性,再灌后逐渐减弱,在所观察的时间范围内,仍显著高于对照水平,而iNOS活性无明显变化,总NOS活性变化主要取决于cNOS活性的改变。结论:脑缺血再灌过程中,脑线粒体中NOS/NO系统激活可能参与了脑组织缺血再灌注损伤。     

亚低温对脑缺血再灌注后大鼠海马齿状回S100β蛋白表达的影响及临床意义

目的:研究大鼠脑缺血再灌注损伤后海马齿状回S100β蛋白的变化规律,探讨亚低温对脑缺血再灌注损伤的保护作用.方法:采用线栓法制备大鼠缺血再灌注动物模型,将大鼠分为亚低温组、常温组,假手术对照组.分别在不同时间点断头取脑,取材前应用神经功能等级评分观察脑缺血再灌注后行为功能的恢复,连续切片作S100β的免疫组化染色,行S100β阳性细胞计数,应用透射电镜观察大鼠海马齿状回超微结构的改变.结果:常温组再灌注4d开始、亚低温组于再灌注2d开始神经功能等级评分逐渐减低,亚低温组于6d、8d、10d评分减低与常温组相应时间点比较有显著性差异(P＜0.05);常温组缺血侧再灌注1d～4d S100β阳性细胞数明显增多,4d时达高峰,此后逐渐减少,10d时降至假手术组水平.亚低温组缺血侧S100β蛋白其阳性细胞数在2d、4d、6d、8d均显著高于常温组的相应时间点(P＜0.01);亚低温组脑组织超微结构损伤较常温组相应时间点明显减轻.结论:脑缺血过程中早期应用亚低温可减轻脑组织损伤,促进脑缺血后神经功能恢复,其机理可能与增加脑组织中S100β表达有关.     

Postischaemic changes in protein synthesis in the rat brain: effects of hypothermia

Protein synthesis, measured as [¹⁴C]-leucine incorporation into proteins, was studied in the normothermic rat brain following 15 min of transient cerebral ischaemia and 1 h, 24 h and 48 h of recirculation, and in the hypothermic (33°C) brain following 1 h and 48 h of recirculation. Ischaemia was induced by bilateral common carotid occlusion combined with hypotension. Following normothermic ischaemia, incorporation of [¹⁴C]-leucine was depressed by 40–80% at 1 h of recirculation in all brain regions studied. At 48 h postischaemia, incorporation returned to normal or above normal levels in the inner layers of neocortex, the CA3 region, the striatum and the dentate gyrus, while in the outer layers of neocortex and in the hippocampal CA1 region the incorporation was persistently decreased by 26% and 40% respectively. At 24 and 48 h postischaemia, protein synthesis in the CA1 region and the striatum could be attributed to proliferating microglia. Intra-ischaemic hypothermia ameliorated the persistent depression of protein synthesis in the CA1 region at 48 h postischaemia, and a two-fold increase compared to the normothermic group was observed both in the CA1 region and the striatum. In the cortex, eucaryotic initiation factor 2 activity transiently decreased at 30 min postischaemia. In animals subjected to intra-ischaemic hypothermia, the eucaryotic initiation factor 2 activity was reduced by 50% of control at 30 min of recirculation compared with 77% in normothermic animals. We conclude that the postischaemic depression of protein synthesis is in part caused by a decrease in eucaryotic initiation factor 2 activity. The early postischaemic depression may reflect a reaction of the tissue to stress, while the late persistent depression, which is normalised by intra-ischaemic hypothermia, may be related to the mechanism of cell death.     

Effect of hypothermia on brain cell membrane function and energy metabolism after transient global hypoxia-ischemia in the newborn piglet.

This study was done to determine the effects of hypothermia on brain cell membrane function and energy metabolism after transient hypoxia-ischemia (HI) in the newborn piglet. Cerebral HI was induced by temporarily complete occlusion of bilateral common carotid arteries with surgical clips and simultaneous breathing with 8% oxygen for 30 min, followed by release of carotid occlusion and normoxic ventilation for 4 hr. Rectal temperature was maintained between 38.0 and 39.0 degrees C in normothermic groups, and between 34.0 and 35.0 degrees C in hypothermic groups for 4 hr after HI. During HI, heart rate, glucose and lactate level in the blood and cerebrospinal fluid increased, and base excess, pH and blood pressure decreased significantly in both normothermic and hypothermic groups. After HI, these abnormalities returned to normal in normothermic group, but lactic acidosis persisted in hypothermic group. Decreased cerebral Na+,K+- ATPase activity and increased lipid peroxidation products, indicative of HI- induced brain injury, were more profound in hypothermic group than in normothermic group. Brain ATP and phosphocreatine levels were not different between normothermic and hypothermic groups. In summary, hypothermia applied immediately after HI for 4 hr did not improve the recovery of brain cell membrane function and energy metabolism in the newborn piglet.     

Hypoxic ischaemic hypothermia promotes neuronal differentiation and inhibits glial differentiation from newly generated cells in the SGZ of the neonatal rat brain

Hypothermia is a potential therapy for cerebral hypoxic ischaemic injury in adults and neonates. The mechanism of the neuroprotective effects of hypothermia after hypoxia-ischaemia (HI) in the developing rat brain remains unclear. In this research, 7-day-old rats underwent left carotid artery ligation followed by the administration of 8% oxygen for 2 h. These rats were divided into hypothermic (rectal temperature, 32-33 °C for 24 h) and normothermic (36-37 °C for 24 h) groups immediately after HI. All rats were given 50 mg/kg/day 5-bromodeoxyuridine (BrdU) intraperitoneally at 4-6 days and sacrificed at 1 or 2 weeks after HI. We found a significant decrease in infarct volume and the neuron loss were also detected in the subgranular zone (SGZ) in the hypothermic group at 7 and 14 days after HI compared with the normothermic group. BrdU immunopositive cells were reduced greatly in the hypothermic group compared with the normothermic group. Hypothermia did not change the number of nestin-labelled cells in the ipsilateral SGZ at 1 and 2 weeks after HI. The differentiation of newly generated cells was assessed by double immunolabelling of BrdU with glial fibrillary acidic protein (GFAP), O4 or Neuronal Nuclei (NeuN). The ratio of BrdU(+)-GFAP(+) or BrdU(+)-O4(+) to total BrdU(+) staining decreased dramatically, but the ratio of BrdU(+)-NeuN(+) to total BrdU(+) staining increased significantly in the hypothermic group compared to the normothermic group at 2 and 6 weeks after HI. These results suggest that the reduction in neuron loss observed after mild hypothermia may be associated with enhanced neuronal differentiation and decreased glial differentiation in the SGZ after HI. These observations are noteworthy for clinical hypothermia therapy following cerebral HI injury during the perinatal period.     

Differential fall in ATP accounts for effects of temperature on hypoxic damage in rat hippocampal slices

Intracellular recordings, ATP and cytosolic calcium measurements from CA1 pyramidal cells in rat hippocampal slices were used to examine the mechanisms by which temperature alters hypoxic damage. Hypothermia (34 degrees C) preserved ATP (1.7 vs. 0.8 nM/mg) and improved electrophysiologic recovery of the CA1 neurons after hypoxia; 58% of the neurons subjected to 10 min of hypoxia (34 degrees C) recovered their resting and action potentials, while none of the neurons at 37 degrees C recovered. Increasing the glucose concentration from 4 to 6 mM during normothermic hypoxia improved ATP (1.3 vs. 0.8 nM/mg) and mimicked the effects of hypothermia; 67% of the neurons recovered their resting and action potentials. Hypothermia attenuated the membrane potential changes and the increase in intracellular Ca(2+) (212 vs. 384 nM) induced by hypoxia. Changing the glucose concentration in the artificial cerebrospinal fluid primarily affects ATP levels during hypoxia. Decreasing the glucose concentration from 4 to 2 mM during hypothermic hypoxia worsened ATP, cytosolic Ca(2+), and electrophysiologic recovery. Ten percent of the neurons subjected to 4 min of hypoxia at 40 degrees C recovered their resting and action potentials; this compared with 60% of the neurons subjected to 4 min of normothermic hypoxia. None of the neurons subjected to 10 min of hypoxia at 40 degrees C recovered their resting and action potentials. Hyperthermia (40 degrees C) worsens the electrophysiologic changes and induced a greater increase in intracellular Ca(2+) (538 vs. 384 nM) during hypoxia. Increasing the glucose concentration from 4 to 8 mM during 10 min of hyperthermic hypoxia improved ATP (1.4 vs. 0.6 nM/mg), Ca(2+) (267 vs. 538 nM), and electrophysiologic recovery (90 vs. 0%). Our results indicate that the changes in electrophysiologic recovery with temperature are primarily due to changes in ATP and that the changes in depolarization and Ca(2+) are secondary to these ATP changes. Both primary and secondary changes are important for explaining the improved electrophysiologic recovery with hypothermia.     

3-硝基丙酸预处理对脑缺血耐受模型GLUT1和GLUT3表达的影响

目的: 探讨3-硝基丙酸(3-NPA)预处理对大鼠局灶性脑缺血半暗带区不同再灌注时点GLUT1和GLUT3 mRNA及蛋白水平表达的影响。方法: 雄性SD大鼠40只,随机分为假手术组(sham组,n=4)、预处理对照组(3-NPA组,n=4)、大脑中动脉缺血组(M组,n=16)、3-NPA 预处理组(IPC组,n=16)。M组和IPC组按再灌注时间(4 h、12 h、24 h及48 h)不同又分为4个亚组,每组动物4只。将大鼠在相应时点断头取脑,取缺血侧(左侧)冠状面中间1/3皮质,分别采用RT-PCR和Western blotting方法检测GLUT1、GLUT3 mRNA和蛋白水平表达情况。结果: IPC组GLUT1 mRNA表达在缺血再灌注后4 h开始升高,48 h最大,显著高于sham组和M组相应时点。IPC组GLUT3 mRNA表达在24 h增高,48 h最高,与M组相应时点24 h、48 h及sham组比较显著增高。IPC组比M组的GLUT1蛋白、GLUT3蛋白表达增高,有显著差异(F=5.848,P<0.05;F=6.295,P<0.05),尤以缺血再灌注后48 h两者差异最明显。结论: 3-NPA预处理能诱导脑缺血耐受,其机制可能是上调GLUT1和GLUT3 mRNA及蛋白表达水平,维持脑组织的能量供给。     

金黄色葡萄球菌胞壁成分在细菌性眼内炎中的致病作用

目的:观察并比较金黄色葡萄球菌胞壁及其成分在大鼠眼内的致炎特性。方法:将大鼠随机分为热灭活细菌组(96只,注射热灭活细菌10μg)、热灭活细菌碎片组(96只,注射热灭活细菌碎片10μg)、肽聚糖组(96只,注射肽聚糖10μg)和对照组(96只,注入等量无菌生理盐水)。在玻璃体腔注入药物后6、12、24、48、72h和5d,裂隙灯显微镜下进行眼部炎症评分,组织病理学切片进行眼内浸润白细胞计数,并测定玻璃体内肿瘤坏死因子(TNF)-α、白细胞介素(IL)-1β及中性粒细胞趋化因子(CINC)-1的表达水平和前房水蛋白质浓度。结果:在注射后6-72h,热灭活细菌组、热灭活细菌碎片组及肽聚糖组眼内均可见严重的炎症反应,至术后5d炎症基本消退。各组眼内白细胞的浸润数量在术后24h达到高峰[热灭活细菌组(207.1±33.7)细胞/眼;热灭活细菌碎片组(514.2±116)细胞/眼,与热灭活细菌组比较,P0.05;肽聚糖组(412.6±191)细胞/眼,与热灭活细菌组比较,P0.05],至术后3d浸润细胞数量迅速下降。各组TNF-α的浓度在术后24h均达到高峰[热灭活细菌组(178.3±76.5)ng/L;热灭活细菌碎片组(353.2±141.3)ng/L,与热灭活细菌组比较,P0.05;肽聚糖组(311.2±99.8)ng/L,与热灭活细菌组比较,P0.05],并持续至术后48h,随后迅速下降,并在术后5d回复至基线水平。各组IL-1β浓度在术后24h均达到高峰[热灭活细菌组(637.8±277.7)ng/L;热灭活细菌碎片组(1922.0±670.3)ng/L,与热灭活细菌组比较,P0.05;肽聚糖组(1517.0±420.2)ng/L,与热灭活细菌组比较,P0.05],并持续至术后48h,随后迅速下降,并在术后5d回复至基线水平。各组CINC-1的浓度在术后12h均达到高峰[热灭活细菌组(1173.3±221.5)ng/L;热灭活细菌碎片组(1864.0±403.4)ng/L,与热灭活细菌组比较,P0.05;肽聚糖组(2536.0±386.3)ng/L,与热灭活细菌组比较,P0.05],并持续至术后24h,随后迅速下降,并在术后3d回复至正常水平。在各观察时点,均可观察到眼内炎组房水蛋白质浓度较对照组显著增高(P0.01)。结论:金黄色葡萄球菌胞壁及其成分可在SD大鼠诱导出典型的实验性眼内炎。大量白细胞眼内浸润、血眼屏障的破坏、TNF-α和IL-1β的高水平表达是实验性眼内炎模型的主要病理特点。与完整的热灭活金黄色葡萄球菌比较,细菌碎片及其成分肽聚糖具有更强烈的眼内促炎能力。     

Hypothermia related changes in electrocortical activity at stepwise increase of intracranial pressure in piglets.

Recent experimental studies have demonstrated that mild hypothermia can be effective in the control of intracranial hypertension. However, investigations to analyze the effects of hypothermia on changes in brain oxygen metabolism and electrocortical activity caused by increased intracranial pressure (ICP) are lacking. We examined the effects of mild hypothermia on electrocorticogram (ECoG) in combination with measurement of regional cerebral blood flow (CBF) and estimation of brain oxygen metabolism during stepwise increase of ICP. For this purpose thirteen female piglets (14 days old, 4-5 kg b.w.) were anaesthetized and mechanically ventilated. An epidural balloon was gradually inflated in order to increase ICP to 25 mmHg, 35 mmHg and 45 mmHg every 30 minutes at adjusted mean arterial blood pressures (MAP). This procedure resulted in gradual cerebral perfusion pressure (CPP) reduction of about 70%, 50%, and 30% of baseline [baseline CPP: normothermia (NT) 80+/-3 mmHg; hypothermia (HT) 84+/-3 mmHg]. Control animals were maintained in a normothermic state (38.6+/-0.2 degrees C). HT animals were surface cooled and maintained at 31.9+/-0.1 degrees C. ECoG, regional CBF, cerebral oxygen delivery (cDO2) and the cerebral metabolic rate of oxygen (CMRO2) were estimated during the normothermic period, after hypothermic stabilization, and after the gradual CPP reductions. The baseline ECoG showed the typical delta-dominated frequency pattern for isoflurane anaesthesia. At the hypothermic level, a frequency shift was seen from delta activity towards the higher frequencies (theta- and alpha activity) and the total spectral power was significantly reduced (56+/-17% from baseline, p < 0.05). the cortical CBF decreased markedly to 67+/-10% (p < 0.05), whereas the medulla oblongata blood flow increased slightly. During controlled increase of ICP by regional mass expansion from epidural balloon inflation, we found at mild and moderate stages of ICP increase (25 and 35 mmHg) only minimal changes in the ECoG in hypothermic animals compared to the hypothermic baseline, whereas the ECoG in normothermic animals showed a marked decrease in frequency, amplitude and total spectral power. We conclude that mild hypothermia produces an arousal-like ECoG activity with marked frequency shift to alpha activity and a change from high to low voltage activity. Furthermore, the hypothermic brain showed a preserved neuronal function at moderate stages of ICP. Obviously, hypothermia improves the functional tolerance of the brain to impaired oxygen supply.