Propofol prevents delayed neuronal death following transient forebrain ischemia in gerbils

PURPOSE: This study was conducted to ascertain whether propofol may protect against delayed neuronal death in the hippocampal CA1 subfield in gerbils. METHODS: Thirty-five gerbils were randomly assigned to five groups: Group I, the control group, a sham operation treated with physiological saline solution (PSS); Group II, ischemia/reperfusion treated with PSS; Group III, ischemia/reperfusion treated with 50 mg x kg(-1) propofol; Group IV, ischemia/reperfusion treated with 100 mg x kg(-1) propofol; Group V ischemia/reperfusion treated with 150 mg x kg(-1) propofol. Transient forebrain ischemia was induced by occluding the bilateral common carotid arteries for four minutes under N2O/O2/halothane anesthesia after administration of propofol or PSS. Five days later, histopathological changes in the hippocampal CA1 subfield were examined using a light microscope and degenerative ratio of the pyramidal cells were measured according to the following formula: (number of degenerative pyramidal cell/total number of pyramidal cells per 1 mm of hippocampal CA1 subfield) x 100. RESULTS: In group II, the pyramidal cells were atrophic and pycnotic; vacuolation and structural disruption of the radial striated zone was observed. In the other four groups, these changes were not observed. The degenerative ratios of pyramidal cells were as follows; group I: 5.9 +/- 1.9%, group II: 94.6 +/- 2.5% (P < 0.01), group III: 10.7 +/- 1.7%, group IV: 9.7 +/- 1.8%, group V: 9.2 +/- 1.9%. CONCLUSION: This study suggests that propofol may prevent delayed neuronal death in the hippocampal CA1 subfield after cerebral ischemia/reperfusion in gerbils.     

Propofol prevents lipid peroxidation following transient forebrain ischemia in gerbils

PURPOSE: To ascertain whether propofol prevents lipid peroxidation on delayed neuronal death induced by transient forebrain ischemia in the hippocampal CA1 subfield in gerbils. METHODS: Forty gerbils were randomly assigned to five groups: Group I, control, sham operation treated with physiological saline solution (PSS); Group II, ischemia/reperfusion treated with PSS; Group III, ischemia/reperfusion treated with 50 mg x kg(-1) propofol; Group IV, ischemia/reperfusion treated with 100 mg x kg(-1) propofol; Group V, ischemia/reperfusion treated with 150 mg x kg(-1) propofol. Transient forebrain ischemia was induced by occluding the bilateral common carotid arteries for four minutes under N2O/O2/halothane anesthesia after propofol or PSS. Five days later, the cerebrum was removed and each forebrain was cut into two including the hippocampus. Lipid peroxidation was determined using the production of malondialdehyde (MDA), and histopathological changes in the hippocampal CA1 subfield were examined. RESULTS: In group II, the pyramidal cells were atrophic and pycnotic; vacuolation and structural disruption of the radial striated zone was observed. In the other four groups, these changes were not observed. Degenerative ratios of pyramidal cells were: Group I: 4.9 +/- 2.3, Group II: 94.1 +/- 4.5 (P < 0.01), Group III: 12.5 +/- 5.7, Group IV: 11.0 +/- 4.6, Group V: 9.6 +/- 4.9%. Production of MDA was: Group I: 83 +/- 22, Group II: 198 +/- 25 (P < 0.01), Group III: 153 +/- 39, Group IV: 113 +/- 34, Group V: 106 +/- 27 nmol x g(-1) wet tissue. CONCLUSION: Propofol attenuated delayed neuronal death by preventing lipid peroxidation induced by transient forebrain ischemia in the hippocampal CA1 subfield in gerbils.     

灯盏花素对沙土鼠缺血再灌注损伤的影响

目的 研究灯盏花素对沙土鼠缺血再灌注后海马延迟性神经元死亡的影响。方法 脑缺血10分钟建立沙土鼠缺血再灌注模型。32例沙土鼠分为假手术组。对照组、灯盏花素10mg/kg组和灯盏花素20mg/kg组。应用开阔法检查观察各组沙土鼠行为变化,应用病理检查判断脑缺血后神经细胞延迟性死亡情况。结果 灯盏花素明显减轻脑缺血后沙土鼠行为受损程度,减少海马CAI区锥体细胞的死亡数目。结论 灯盏花素能减轻沙土鼠缺血再灌注损伤。     

Effects of Pre- and Postischemic Administration of Thiopental on Transmitter Amino Acid Release and Histologic Outcome in Gerbils

Background: The mechanism by which barbiturates protect neurons against ischemia is unclear, particularly when they are given after ischemia or reperfusion begins. Because an excess release of excitatory neurotransmitters causes postsynaptic membrane depolarization, which triggers neuronal damage in ischemia, the effects of thiopental on histologic outcome, ischemia-induced amino acid release, and anoxic depolarization in gerbils were studied.

Methods: The effects of different doses of thiopental administered before or after ischemia were examined morphologically by assessing delayed neuronal death in hippocampal CA1 pyramidal cells produced by forebrain ischemia for 3 min in gerbils. The ischemia-induced changes in output of aspartate, glutamate, glycine, taurine, and gamma-aminobutyric acid were measured using a microdialysis-high-performance liquid chromatography procedure, and the differences among a halothane-anesthetized group, a thiopental-administered group, and a group given thiopental after a period of ischemia were evaluated. The changes induced in the direct-current potential in the hippocampal CA1 area by forebrain ischemia were compared in animals anesthetized with halothane and those given thiopental.

Results: Preischemic administration of thiopental at all doses decreased the risks for delayed neuronal death (P < 0.01). Post-ischemic administration at a dosage of 2 mg [centered dot] kg sup -1 [centered dot] min sup -1 for 60 min protected neurons, but the same dose for 10 min did not ameliorate the cell injury. Forebrain ischemia produced marked increases in all amino acids 3 to 6 min after the start of recirculation in the halothane-anesthetized gerbils, whereas thiopental anesthesia (2 mg [centered dot] kg sup -1 [centered dot] min sup -1) reduced these increases throughout the experimental period, except for glycine (P < 0.01). The initiation of thiopental after reflow did not markedly diminish these increases. Thiopental anesthesia prolonged the onset of anoxic depolarization and reduced its maximal amplitude.     

Protective effects of cyclosporine and allopurinol on transient global cerebral ischemia in gerbils

The effects of cyclosporine and allopurinol on neuronal death following global cerebral ischemia were evaluated in Mongolian gerbils. The animals were randomly divided into four groups of 12 each: (1) sham operation as control, (2) occlusion of the bilateral common carotid arteries for 12 min and treatment with physiological saline, (3) occlusion plus treatment with 5 mg/kg of cyclosporine, and (4) occlusion plus treatment with 100 mg/kg of allopurinol 30 min before cerebral ischemia and daily thereafter for 6 days. On the 7th day after ischemia or sham operation, the gerbils' brains were removed. The number of necrotic pyramidal cells in the cortex and hippocampal CA1 was evaluated and tissue chemiluminescence (reflecting the presence of superoxide radicals) and lipid peroxides were examined. The number of necrotic pyramidal cells in each field of view (×100) of the cortex was 115±79 after ischemia, which was significantly larger than 14±8 in the control group, and was 45±33 and 60±49 after treatment with cyclosporine and allopurinol, respectively. The number of surviving pyramidal cells per mm length after ischemia in CA1 was 37±14, which was significantly smaller than 174±30 in the control group, but 78±31 following treatment with was cyclosporine, and 108±53 with allopurinol. A reduced number of necrotic pyramidal cells was associated with lower tissue chemiluminescence and lipid peroxides. The results suggest that both cyclosporine and allopurinol can inhibit neuronal death after global cerebral ischemia, and that autoimmunization and superoxide radicals are partially responsible for neuronal death.     

Effects of dantrolene on extracellular glutamate concentration and neuronal death in the rat hippocampal CA1 region subjected to transient ischemia

BACKGROUND: Excessive extracellular glutamate produced by cerebral ischemia has been proposed to initiate the cascade toward neuronal cell death. Changes in extracellular glutamate concentration are closely linked to changes in intracellular calcium ion concentration. Dantrolene inhibits calcium release from intracellular calcium stores. In this study, the authors investigated the effects of dantrolene on extracellular glutamate accumulation and neuronal degeneration in a rat model of transient global forebrain ischemia. METHODS: Male Wistar rats weighing 230-290 g were anesthetized with halothane in nitrous oxide-oxygen and were subjected to 10 min of transient forebrain ischemia using a four-vessel occlusion technique. Fifteen minutes before ischemic injury, dantrolene sodium (5 mm), dimethyl sulfoxide as a vehicle for dantrolene, or artificial cerebrospinal fluid as a control was intracerebroventricularly administered (n = 8 in each group). In the hippocampal CA1 subfield, the extracellular glutamate concentration in vivo was measured during the periischemic period with a microdialysis biosensor, and the number of intact neurons was evaluated on day 7 after reperfusion. RESULTS: Both dantrolene and dimethyl sulfoxide significantly reduced the ischemia-induced increase in glutamate concentration to a similar extent, i.e., by 53 and 51%, respectively, compared with artificial cerebrospinal fluid (P < 0.01). The number of intact hippocampal CA1 neurons (mean +/- SD; cells/mm) in dantrolene-treated rats (78 +/- 21) was significantly higher than that in artificial cerebrospinal fluid- (35 +/- 14; P < 0.001) and dimethyl sulfoxide-treated (56 +/- 11; P < 0.05) animals. Dimethyl sulfoxide also significantly increased the number of preserved neurons in comparison with artificial cerebrospinal fluid (P < 0.05). CONCLUSIONS: Intracerebroventricular dantrolene prevents delayed neuronal loss in the rat hippocampal CA1 region subjected to transient ischemia; however, this neuroprotection cannot be accounted for only by the reduced concentrations of extracellular glutamate during ischemia.     

Superoxide radical generation and histopathological changes in hippocampal CA1 after ischaemia/ reperfusion in gerbils

Purpose

We investigated the relationship between the generation of Superoxide radicals and histopathological changes on delayed neuronal death in the hippocampal CA1 subfield.

Methods

Seventy gerbils were randomly assigned to two groups, a sham group and an ischaemia/reperfusion (I/R) group. In the I/R group, transient forebrain ischaemia was induced by occluding the bilateral common carotid arteries for four minutes. The cerebrum was removed after reperfusion at intervals of one minute, six, twelve and twenty-four hr and at three, five and seven days. Each forebrain was cut into two portions including the hippocampus. The quantity of Superoxide radicals was measured by using chemiluminescence, and histopathological changes in the hippocampal CAI subfield were examined.

Results

In the I/R group, Superoxide radicals increased on the 3rd and 5th days compared with the sham group (16.1 ±3.4vs3.2± 1.0 on the third day (P < 0.0001 ); 10.9 ± 1.9 vs 3.3 ± 0.8 on the fifth day (P < 0.0001)). In the I/R group, the pyramidal cells were atrophic and pycnotic; vacuolation, and structural disruption of the radial striated zone were observed from the third through the seventh day. In the sham group, these changes were not observed. There were differences of degenerative ratios in the pyramidal cells between the two groups from the third to seventh days (5.6 ± 2.0 vs 80.9 ± 3.3 on the third day (P < 0.05); 6.9 ± 0.4 vs 93.6 ± 2.4 on the fifth day (P < 0.05); 6.2 ± 1.5 vs 95.0 ± 1.3 on the seventh day (P < 0.05)).

Conclusion

There is a correlation between the generation of Superoxide radicals and histopathological changes of the pyramidal cells in the hippocampal CAI subfield.     

Effect of hyperbaric oxygen therapy or dimethyl sulfoxide on cerebral ischemia in unanesthetized gerbils

To determine whether treatment with hyperbaric oxygen (HBO) or dimethyl sulfoxide (DMSO) could mitigate the fatal effects of cerebral ischemia, we anesthetized 68 gerbils with ketamine, ligated the right carotid artery (CA), and placed a snare occluder around the left CA. After 48 hours, 30 gerbils that were neurologically normal or had suffered only mild deficits were subjected to left CA occlusion without anesthesia for periods of 2 to 60 minutes. The onset of circling, posturing, falling, and lethargy began immediately; seizures and coma ensued 4 to 5 minutes later and persisted until release of the left CA occluder. All gerbils recovered after 2-minute staged bilateral CA occlusions. The mortality rate was 33% after both 5- and 10-minute occlusions and 100% after 20- and 60-minute bilateral occlusions. Twelve gerbils were placed in an HBO chamber (100% oxygen at 1.5 atmospheres) for 15 minutes during 20-minute bilateral occlusion; only 2 died (16% mortality rate). Thus, HBO therapy conferred significant protection against death from untreated ischemia (P less than 0.001). Histological examination showed that the extent of patchy bilateral ischemic neuronal damage was much less in surviving gerbils that received HBO therapy than in those that died after 20-minute occlusions. Fourteen gerbils were treated with DMSO, 2.5 g/kg intraperitoneally, during 5- or 10-minute bilateral CA occlusion; 12 died (86% mortality rate). Thus, DMSO provided no protection against fatal cerebral infarction; in fact, the results in the 10-minute reperfusion group suggest that DMSO may have a deleterious effect.     

Effect of Nitrous Oxide on Neuronal Damage and Extracellular Glutamate Concentration as a Function of Mild, Moderate, or Severe Ischemia in Halothane-anesthetized Gerbils

Background: The effect of nitrous oxide on ischemic neuronal damage was quantitatively evaluated by use of logistic regression curves.

Methods: Seventy-two gerbils were anesthetized with 1% halothane and randomly assigned to receive 70% nitrous oxide or 70% nitrogen. Forebrain ischemia was performed for 3, 5, or 7 min, and direct-current potential in the hippocampal CA1 region was recorded. Histologic outcome was evaluated 5 days later. Relations of neuronal damage with ischemic duration and duration of ischemic depolarization were determined by logistic regression curves. In some animals, extracellular glutamate concentration was measured every 60 s during forebrain ischemia.

Results: Nitrous oxide increased neuronal damage only with 5 min of ischemia (nitrous oxide vs. nitrogen: 78.5 +/- 23.0 vs. 37.3 +/- 12.2%; P < 0.01). The percentages of neuronal damage with 3 and 7 min of ischemia were not different with or without nitrous oxide. Logistic regression curves indicated that nitrous oxide significantly increased neuronal damage during the period from 3.07 to 6.63 min of ischemia. Logistic regression curves also indicated that nitrous oxide increased neuronal damage in the condition of the same duration of ischemic depolarization. Nitrous oxide shortened the ischemic duration necessary for causing 50% neuronal damage by 0.82 min. Dynamic change in extracellular glutamate concentration was not different (mean maximum dialysate glutamate concentration: 4.29 +/- 3.09 vs. 4.63 +/- 1.83 [mu]m).     

Effects of Dantrolene on Extracellular Glutamate Concentration and Neuronal Death in the Rat Hippocampal CA1 Region Subjected to Transient Ischemia

Background: Excessive extracellular glutamate produced by cerebral ischemia has been proposed to initiate the cascade toward neuronal cell death. Changes in extracellular glutamate concentration are closely linked to changes in intracellular calcium ion concentration. Dantrolene inhibits calcium release from intracellular calcium stores. In this study, the authors investigated the effects of dantrolene on extracellular glutamate accumulation and neuronal degeneration in a rat model of transient global forebrain ischemia.

Methods: Male Wistar rats weighing 230-290 g were anesthetized with halothane in nitrous oxide-oxygen and were subjected to 10 min of transient forebrain ischemia using a four-vessel occlusion technique. Fifteen minutes before ischemic injury, dantrolene sodium (5 mm), dimethyl sulfoxide as a vehicle for dantrolene, or artificial cerebrospinal fluid as a control was intracerebroventricularly administered (n = 8 in each group). In the hippocampal CA1 subfield, the extracellular glutamate concentration in vivo was measured during the periischemic period with a microdialysis biosensor, and the number of intact neurons was evaluated on day 7 after reperfusion.

Results: Both dantrolene and dimethyl sulfoxide significantly reduced the ischemia-induced increase in glutamate concentration to a similar extent, i.e., by 53 and 51%, respectively, compared with artificial cerebrospinal fluid (P < 0.01). The number of intact hippocampal CA1 neurons (mean +/- SD; cells/mm) in dantrolene-treated rats (78 +/- 21) was significantly higher than that in artificial cerebrospinal fluid- (35 +/- 14;P < 0.001) and dimethyl sulfoxide-treated (56 +/- 11;P < 0.05) animals. Dimethyl sulfoxide also significantly increased the number of preserved neurons in comparison with artificial cerebrospinal fluid (P < 0.05).     

Continuous fluid resuscitation and splenectomy for treatment of uncontrolled hemorrhagic shock after massive splenic injury

BACKGROUND: Using a standardized massive splenic injury (MSI) model of uncontrolled hemorrhagic shock, we studied the effect of continuous fluid resuscitation and splenectomy on the hemodynamic response and survival in rats. METHODS: The animals were randomized into seven groups: group 1 (n = 8), sham-operated; group 2 (n = 8), MSI untreated; group 3 (n = 8), MSI treated with 7.5 mL/kg/h of 7.5% NaCl (hypertonic saline [HTS]) for 1 hour; group 4 (n = 8), MSI treated with 7.5 mL/kg/h hydroxyethyl starch (HES-7.5) for 1 hour; group 5 (n = 8) MSI treated with 35 mL/kg/h Ringer's lactate (RL) solution (RL-35) for 1 hour; group 6 (n = 8) MSI treated with 70 mL/kg/h RL for 1 hour (RL-70); and group 7 (n = 8), MSI treated with 105 mL/kg/h RL for 1 hour (RL-105). In all MSI groups, splenectomy was performed 45 minutes after injury. RESULTS: MSI in untreated group 2 resulted in a fall of mean arterial pressure from 105.9 +/- 10.7 mm Hg to 27.0 +/- 6.7 mm Hg (p < 0.001) in 60 minutes. Mean survival time after splenectomy in this group was 160.7 +/- 29.7 minutes, and total blood loss was 34.8 +/- 4.7% of blood volume. Continuous HTS infusion with splenectomy in group 3 was followed by a total blood loss of 38.7 +/- 4.4% and mean survival time was 176.5 +/- 23.2 minutes. HES-7.5 infusion and splenectomy was followed by a total blood loss of 39.6 +/- 2.5% and survival time was 171.6 +/- 19.5 minutes. Continuous infusion of increasing volumes of RL in groups 5, 6, and 7 was followed by increase in blood loss to 29.0 +/- 4.1%, 50.2 +/- 3.1% (p < 0.001), and 62.7 +/- 7.1% (p < 0.002) of total blood volume, respectively. Mean survival time in groups 5, 6, and 7 was 233.5 +/- 6.5 minutes (p < 0.04), 207.6 +/- 17.0 minutes (p < 0.05), and 158 +/- 26 minutes, respectively. CONCLUSION: Continuous infusion of large-volume RL and splenectomy after massive splenic injury resulted in a significant increase in intra-abdominal bleeding and shortened survival time compared with small-volume RL infusion.     

Neuroprotective Effects of Dexmedetomidine in the Gerbil Hippocampus after Transient Global Ischemia

Background: Cerebral ischemia induces a massive release of norepinephrine associated with neuronal death in the brain. It has been demonstrated that alpha2 -adrenoceptor agonists decrease the release and turnover of noradrenaline, and this might prove advantageous in counteracting the neurodegeneration in ischemic brain. Therefore, in the present study, the authors tested whether dexmedetomidine, a selective alpha2 -receptor agonist, has neuroprotective effects in a gerbil transient global ischemia model.

Methods: Ischemia was induced by bilateral carotid occlusion for 5 min in diethylether-anesthetized normothermic gerbils. Dexmedetomidine was administered subcutaneously in four different treatment paradigms (6-8 animals/group): 3 or 30 micro gram/kg 30 min before and thereafter at 3, 12, 24, and 48 h after the occlusion, or 3 or 30 micro gram/kg at 3, 12, 24, and 48 h after the occlusion. Control animals were subjected to forebrain ischemia but received only saline injections. One week after occlusion, animals were transcardially perfused for histochemistry. Neuronal death in the CA1 and CA3 regions of the hippocampus and in the hilus of the dentate gyrus was evaluated in silver-stained 60-micro meter coronal sections.

Results: Compared with saline-treated ischemic animals, dexmedetomidine at a dose of 3 micro gram/kg given before and continued after the induction of ischemia reduced the number of damaged neurons in the CA3 area (2 +/- 3 vs. 17 +/- 20 degenerated neurons/mm2; P <0.05). Also in the dentate hilus, the number of damaged neurons was reduced by dexmedetomidine (3 micro gram/kg) given before and continued after ischemia (5 +/- 7 vs. 56 +/- 42 degenerated neurons/mm2; P <0.01).     

Hypertonic sodium resuscitation is associated with renal failure and death.

OBJECTIVE: The use of hypertonic sodium solutions (HSS) and lactated Ringer's (LR) solution in the resuscitation of patients with major burns was compared. SUMMARY BACKGROUND DATA: Hypertonic sodium solutions have been recommended for burn resuscitation to reduce the large total volumes required with isotonic LR solution and their attendant complications. METHODS: To evaluate the efficacy of this therapy in our adult burn center, we resuscitated 65 consecutive patients with HSS (290 mEq/L Na) between July 1991 and June 1993 and compared them with 109 burn patients resuscitated with LR (130 mEq/L Na) between July 1986 and June 1988 (LR-1). A subsequent 39 patients were resuscitated with LR between September 1993 and August 1994 (LR-2). RESULTS: Patients receiving hypertonic sodium solutions versus LR-1 were similar with respect to age (46.0 vs. 43.6 years), total burn size (39.2% vs. 39.9%), incidence of inhalation injury (41.5% vs. 47.7%), and predicted mortality (34.6% vs. 30.2%). Total resuscitation volumes during the first 24 hours were lower among patients treated with HSS than those in the LR-1 group (3.9 +/- 0.3 vs. 5.3 +/- 0.2 mL/kg/% body surface area [BSA], p < 0.05). After 48 hours, however, cumulative fluid loads were similar (6.6 +/- 0.6 vs. 7.5 +/- 0.3 mL/kg/%BSA), and total sodium load was greater with the HSS group (1.3 +/- 0.1 vs. 0.9 +/- 0.1 mEq/kg/%BSA, p < 0.002). During the first 3 days after burn, serum sodium concentrations were moderately elevated in the HSS patients (153 +/- 2 vs. 135 +/- 1 mEq/L, p < 0.001). Patients resuscitated with HSS had a fourfold increase in renal failure (40.0 vs. 10.1%, p < 0.001) and twice the mortality of LR-1 patients (53.8 vs. 26.6%, p < 0.001). In patients resuscitated with HSS, renal failure was an independent risk factor (p < 0.001, by logistic regression). Analysis of these results prompted a return to LR resuscitation (LR-2). Age (41.6 +/- 2.9 years), burn size (37.8 +/- 3.9 %BSA), and incidence of inhalation injury (51.3%) were similar to the earlier groups. Total sodium load was less among LR-2 patients than the HSS group (0.7 +/- 0.1 mEq/kg/%BSA, p < 0.01), but similar to the LR-1 patients. Renal failure developed in only 15.4%, and 33.3% died, similar to the LR-1 group and significantly lower than patients treated with HSS (p < 0.001 and p < 0.05, respectively). CONCLUSION: Hypertonic sodium solution resuscitation of burn patients did not reduce the total resuscitation volume required. Furthermore, it was associated with an increased incidence of renal failure and death. The use of HSS for burn resuscitation may be ill advised.     

Effects of equiosmolar load of 20% mannitol, 7.5% saline and 0.9% saline on plasma osmolarity,haemodynamics and plasma concentrations of electrolytes

OBJECTIVES: Mannitol 20% (M) and NaCl 7.5% (H) are hypertonic solutions used in-patient in hypovolaemic shock and in case of increased ICP. To our knowledge no study in humans compared them in an equiosmolar load. The objectives of this study were to compare the pharmacokinetics of both solutions in an equiosmolar load with an isotonic solution (NaCl 0.9% (C)) in terms of osmolarity, electrolytes and haemodynamic parameters over time. STUDY DESIGN: Prospective, randomized, controlled study. PATIENTS: Thirty ASA I and II patients undergoing non haemorrhagic surgery under general anesthesia. METHODS: Three groups were studied (groups M, H and C), each receiving an equiosmolar load (4.95 mOsm kg(-1)) of solutions of mannitol 20%, saline 7.5% and saline 0.9% over ten minutes. Vital parameters (non invasive blood pressure, heart rate, oesophageal temperature) were monitored and blood samples (hemoglobin, hematocrit, K(+), Na(+), Cl(-), urea, creatinine, glucose, mannitolemia, osmolarity) were assessed preoperatively and intraoperatively at times 0, 3, 5, 10, 15, 30, 45, 60, 90, 120, 150 min of perfusion. RESULTS: In both hypertonic groups, osmolarity was maximal at the end of infusion (group M: 329 +/- 7 mOsm l(-1); group H: 321 +/- 11 mOsm l(-1)); at the same time, Na(+) value was lowest in group M: 129 +/- 3 mmol l(-1) and highest in group H: 151 +/- 5 mmol l(-1), P < 0.001) with normalisation at 60 min. These results were also statistically significant when compared to the isotonic group (group C: osmolarity: 296 +/- 3 mOsm l(-1), P < 0.001; Na(+): 140 +/- 2 mmol l(-1), P < 0.001). Plasma volume expansion was statistically significantly larger in-group C between 10 and 15 min compared to both hypertonic groups (haematocrit: group C: 35 +/- 4%, group M: 39 +/- 5%; group H: 41 +/- 3%, P < 0.004). Haemodynamic parameters were similar in the 3 groups with however a trend towards lowers HR in the mannitol group, particularly at T10. Temperature was lower in the control group because of the volume infused. Cl(-) was higher in the H group. CONCLUSION: A single infusion of 4.95 mOsm kg(-1) of mannitol 20% or NaCl 7.5% induces a similar osmolar variation over time with a maximal effect after 10 min.     

Fosphenytoin Reduces Hippocampal Neuronal Damage in Rat Following Transient Global Ischemia

Summary Fosphenytoin, a water-soluble disodium phosphate ester of phenytoin, is a phenytoin prodrug with similar anticonvulsant properties. In this study, we evaluated its neuroprotective properties in a cardiac arrest-induced global ischemia model. After 12 minute ischemia, Long-Evans hooded rats were resuscitated, given fosphenytoin (30 mg/kg, i.m.) or saline 5 minutes after the ischemic episode, and killed on day 7. Brains were removed, fixed, and vibratome sectioned to assess the numbers of normal appearing CAI pyramidal neurons and for immunohistological staining of glial fibrillary acidic protein (GFAP). After global ischemia, the number of hippocampal CA1 pyramidal neurons decreased significantly (from 14.33±1.73 to 2.19±0.16 per 100 μm²). Most hippocampal CA1 pyramidal neurons showed signs of injury and GFAP immunoreactivity of the region increased. With fosphenytoin treatment 5 min after ischemia, hippocampal CA1 pyramidal neurons remained at near control level (13.90±0.92), however, GFAP staining was not significantly changed. Our data, although indicating different neuronal and glial responses following fosphenytoin treatment, nevertheless, suggest that fosphenytoin is an effective neuroprotectant against ischemia-induced damage.     

Isoflurane Prevents Delayed Cell Death in an Organotypic Slice Culture Model of Cerebral Ischemia

Background: General anesthetics reduce neuronal death caused by focal cerebral ischemia in rodents and by in vitro ischemia in cultured neurons and brain slices. However, in intact animals, the protective effect may enhance neuronal survival for only several days after an ischemic injury, possibly because anesthetics prevent acute but not delayed cell death. To further understand the mechanisms and limitations of volatile anesthetic neuroprotection, the authors developed a rat hippocampal slice culture model of cerebral ischemia that permits assessment of death and survival of neurons for at least 2 weeks after simulated ischemia.

Methods: Survival of CA1, CA3, and dentate gyrus neurons in cultured hippocampal slices (organotypic slice culture) was examined 2-14 days after 45 min of combined oxygen-glucose deprivation at 37[degrees]C (OGD). Delayed cell death was serially measured in each slice by quantifying the binding of propidium iodide to DNA with fluorescence microscopy.

Results: Neuronal death was greatest in the CA1 region, with maximal death occurring 3-5 days after OGD. In CA1, cell death was 80 +/- 18% (mean +/- SD) 3 days after OGD and was 80-100% after 1 week. Death of 70 +/- 16% of CA3 neurons and 48 +/- 28% of dentate gyrus neurons occurred by the third day after OGD. Both isoflurane (1%) and the N-methyl-d-aspartate antagonist MK-801 (10 [mu]m) reduced cell death to levels similar to controls (no OGD) for 14 days after the injury. Isoflurane also reduced cell death in CA1 and CA3 caused by application of 100 but not 500 [mu]m glutamate. Cellular viability (calcein fluorescence) and morphology were preserved in isoflurane-protected neurons.     

High-dose S(+)- ketamine improves neurological outcome following incomplete cerebral ischemia in rats

PURPOSE: To determine the effects of the non-competitive NMDA-receptor antagonist S(+)-ketamine on neurological outcome in a rat model of incomplete cerebral ischemia. METHODS: Thirty rats were anesthetized, intubated and mechanically ventilated with isoflurane, O2 30% and nitrous oxide 70%. Following surgery animals were randomly assigned to one of the following treatment groups: Rats in group 1 (n = 10,OFF control) received fentanyl (bolus: 10 microg x kg(-1) i.v.; infusion 25 microg x kg(-1) x h(-1)) and N2O 70% / O2. Rats in group 2 (n = 10) received O2 30% in air and low-dose S(+)-ketamine (infusion: 0.25 mg x kg(-1) x min(-1)). Rats in group 3 (n = 10) received O2 30% in air and high-dose S(+)-ketamine (infusion: 1.0 mg x kg(-1) min(-1)). Following 30 min equilibration period ischemia was induced by combined unilateral common carotid artery ligation and hemorrhagic hypotension to 35 mm Hg for 30 min. Plasma catecholamines were assayed before and at the end of ischemia. Neurological deficit was evaluated for three postischemic days. RESULTS: Neurological outcome was improved with high-dose S(+)-ketamine when compared to fentanyl / N2O -anesthetized controls (9 vs. 1 stroke related deaths, P<0.05). Increases in plasma catecholamine concentrations were higher in fentanyl / N2O -anesthetized (adrenaline baseline 105.5+/-92.1 pg x ml(-1), during ischemia 948+/-602.8 pg x ml(-1), P<0.05; noradrenaline baseline 407+/-120.2 pg x ml(-1), ischemia 1267+/-422.2 pg x ml(-1), P <0.05) than in high-dose S(+)-ketamine-treated animals (adrenaline baseline 71+/-79.5 pg x ml(-1), ischemia 237 +/-131.9; noradrenaline baseline 317.9+/-310.5 pg x ml(-1), ischemia 310.5+/-85.7 pg x ml(-1)). CONCLUSION: Neurological outcome is improved following incomplete cerebral ischemia with S(+)-ketamine. Decreases in neuronal injury may be related to suppression of sympathetic discharge.     

Isoflurane prevents delayed cell death in an organotypic slice culture model of cerebral ischemia.

BACKGROUND: General anesthetics reduce neuronal death caused by focal cerebral ischemia in rodents and by in vitro ischemia in cultured neurons and brain slices. However, in intact animals, the protective effect may enhance neuronal survival for only several days after an ischemic injury, possibly because anesthetics prevent acute but not delayed cell death. To further understand the mechanisms and limitations of volatile anesthetic neuroprotection, the authors developed a rat hippocampal slice culture model of cerebral ischemia that permits assessment of death and survival of neurons for at least 2 weeks after simulated ischemia. METHODS: Survival of CA1, CA3, and dentate gyrus neurons in cultured hippocampal slices (organotypic slice culture) was examined 2-14 days after 45 min of combined oxygen-glucose deprivation at 37 degrees C (OGD). Delayed cell death was serially measured in each slice by quantifying the binding of propidium iodide to DNA with fluorescence microscopy. RESULTS: Neuronal death was greatest in the CA1 region, with maximal death occurring 3-5 days after OGD. In CA1, cell death was 80 +/- 18% (mean +/- SD) 3 days after OGD and was 80-100% after 1 week. Death of 70 +/- 16% of CA3 neurons and 48 +/- 28% of dentate gyrus neurons occurred by the third day after OGD. Both isoflurane (1%) and the N-methyl-D-aspartate antagonist MK-801 (10 microm) reduced cell death to levels similar to controls (no OGD) for 14 days after the injury. Isoflurane also reduced cell death in CA1 and CA3 caused by application of 100 but not 500 microm glutamate. Cellular viability (calcein fluorescence) and morphology were preserved in isoflurane-protected neurons. CONCLUSIONS: In an in vitro model of simulated ischemia, 1% isoflurane is of similar potency to 10 microm MK-801 in preventing delayed cell death. Modulation of glutamate excitotoxicity may contribute to the protective mechanism.     

Hippocampal injury and neurobehavioral deficits following hyperglycemic cerebral ischemia: effect of theophylline and ZM 241385.

OBJECT: The effects of the adenosine receptor antagonists theophylline (for A1 and A2) and ZM 241385 (for A2A) on hippocampal injury and Morris water maze (MWM) performance in rats were investigated following normoglycemic and hyperglycemic cerebral ischemia (induced by four vessel occlusion for 10 minutes). METHODS: Theophylline (36 mg/kg), ZM 241385 (1 mg/kg), or an equivalent volume of saline was administered to rats intraperitoneally 30 minutes before ischemia was induced. Moderate hyperglycemia was achieved by intraperitoneal administration of D-glucose (3 g/kg, 15 minutes before induction of ischemia). Morris water maze trials were performed on the 6th. 7th, and 8th days after ischemic insult. After the conclusion of the performance tests, the rat brains were cut into 8-microm sections, stained with cresyl violet and acid fuchsin, and evaluated in a blinded fashion to determine the extent of injury. Theophylline worsened injury in the hippocampus following normoglycemic and hyperglycemic ischemia. Moreover, theophylline significantly (p < 0.05, six animals) worsened latency and learning index (LI) scores during the MWM trials in both normoglycemic and hyperglycemic animals. On the other hand, ZM 241385 had no effect on either ischemic injury or MWM performance in normoglycemic animals. In the animals in the hyperglycemic ischemia group, however, ZM 241385 significantly (p < 0.05, five animals) reduced injury in the CA1 (94.6 +/- 1.7% compared with 79.2 +/- 10.9%), CA3 (26 +/- 12.5% compared with 11.2 +/- 4.3%), and hilum (22.4 +/- 8.1% compared with 11 +/- 5.5%) regions. In addition, ZM 241385 significantly improved latency (52 +/- 29.7 seconds compared with 24.8 +/- 11.2 seconds, p < 0.05) and LI scores (203.2 +/- 33.3 compared with 152.1 +/- 31.8, p < 0.05) in the MWM trials. A statistically significant correlation was also found between hippocampal injury (CA1, CA3, and hilum) and MWM performance. CONCLUSIONS: The results of this study provide further evidence for a neuromodulatory role of adenosine during normoglycemic and hyperglycemic ischemia.     

Neuroprotective effects of propofol in models of cerebral ischemia: inhibition of mitochondrial swelling as a possible mechanism

BACKGROUND: Propofol (2,6-diisopropylphenol) has been shown to attenuate neuronal injury in a number of experimental conditions, but studies in models of cerebral ischemia have yielded conflicting results. Moreover, the mechanisms involved in its neuroprotective effects are yet unclear. METHODS: The authors evaluated the neuroprotective effects of propofol in rat organotypic hippocampal slices exposed to oxygen-glucose deprivation, an in vitro model of cerebral ischemia. To investigate its possible mechanism of action, the authors then examined whether propofol could reduce Ca2+-induced rat brain mitochondrial swelling, an index of mitochondrial membrane permeability, as well as the mitochondrial swelling evoked by oxygen-glucose deprivation in CA1 pyramidal cells by transmission electron microscopy. Finally, they evaluated whether propofol could attenuate the infarct size and improve the neurobehavioral outcome in rats subjected to permanent middle cerebral artery occlusion in vivo. RESULTS: When present in the incubation medium during oxygen-glucose deprivation and the subsequent 24 h recovery period, propofol (10-100 microM) attenuated CA1 injury in hippocampal slices in vitro. Ca2+-induced brain mitochondrial swelling was prevented by 30-100 microM propofol, and so were the ultrastructural mitochondrial changes in CA1 pyramidal cells exposed to oxygen-glucose deprivation. Twenty-four hours after permanent middle cerebral artery occlusion, propofol (100 mg/kg, intraperitoneal) reduced the infarct size by approximately 30% when administered immediately after and up to 30 min after the occlusion. Finally, propofol administered within 30 min after middle cerebral artery occlusion was unable to affect the global neurobehavioral score but significantly preserved spontaneous activity in ischemic rats. CONCLUSIONS: These results show that propofol, at clinically relevant concentrations, is neuroprotective in models of cerebral ischemia in vitro and in vivo and that it may act by preventing the increase in neuronal mitochondrial swelling.