Temporalis Muscle Temperature Research Articles

Abstract PR161

Background & Objectives: Hydrogen gas is widely considered to be a novel antioxidant1). It has been demonstrated that inhalation of hydrogen gas reduced ischemic cerebral injury in several investigations. However, it remains unclear whether the neuroprotective effect of hydrogen gas is reproducible in a rat transient forebrain ischemia model (i.e. the Smith model). The current study was conducted to evaluate the effect of hydrogen gas on histological outcome after 7-day recovery period in rats subjected to transient forebrain ischemia. Materials & Methods: After approval by the animal research committee, male Sprague-Dawley rats were randomly assigned to one of the following 2 groups: control group, or hydrogen gas group (n=6 in each group). In the hydrogen gas group, transient forebrain ischemia was induced by a combination of hemorrhagic hypotension (mean arterial pressure= 40 mmHg) and bilateral carotid artery occlusion following 2.5% of sevoflurane anesthesia. The brain was reperfused 10 minutes after the onset of ischemia, and after 1 hour, the sevoflurane anesthesia was discontinued. 1.3% hydrogen gas inhalation began 10 min prior to the onset of ischemia, and was continued until the discontinuation of the anesthesia. Temporalis muscle temperature was maintained at approximately 37.5 degrees throughout the procedure. In the control group, all treatments were the same as the hydrogen gas group except for the hydrogen gas inhalation. Seven days after ischemia, the rats were sacrificed for histological evaluation. The brain slices were stained with hematoxilin and eosin, and the coronal sections at hippocampal level were examined light-microscopically. The degree of neuronal damage in the CA1 subfield of the hippocampus was assessed using the following scale: 1 = no ischemic neurons; 2 = less than 20% ischemic neurons; 3 = 20~50% ischemic neurons; 4 = 50~80% ischemic neurons; 5 = more than 80% ischemic neurons; 6 = no intact neurons. Statistical analysis was performed with Mann-Whitney U test for group comparison. Results: The median hippocampal injury scale was greater in the control group than in the hydrogen gas group (5[0] vs. 4[2]; median [interquartile range], respectively, p=0.07). Conclusion: The current study indicates that the treatment with 1.3% hydrogen gas is likely to provide a modest neuroprotective effect in a rat transient forebrain ischemia model.

Abstracts from the 3rd Annual Therapeutic Hypothermia and Temperature Management ConferenceMarch 4–5, 2013Miami, FL

Abstracts from the 3rd Annual Therapeutic Hypothermia and Temperature Management ConferenceMarch 4–5, 2013Miami, FL

Dietary soy may not confound acute experimental stroke infarct volume outcomes in ovariectomized female rats

Oestrogen administration can alter experimental stroke outcomes. Soy as a source of phytoestrogens may therefore modulate responses in 'oestrogen-sensitive' stroke models, thus potentially confounding results. We evaluated the effects of dietary soy on acute infarct volumes in a pilot study using a rat focal stroke model. We hypothesized that ovariectomized (OVX) rats fed a soy-rich diet would have smaller acute infarct volumes than rats fed a soy-free diet. OVX rats were randomly assigned to a soy-free (n = 6) or a soy-rich (n = 6) diet for four weeks and weighed weekly. Following the dietary trial, rats underwent 2 h of middle cerebral artery occlusion (MCAO). Mean arterial blood pressure, rectal and temporalis muscle temperatures, arterial blood gases and blood glucose were recorded peri-ischaemia. Rats were euthanized 22 h following 2 h of MCAO. Brains were stained with 2,3,5-triphenyl tetrazolium chloride for acute infarct volume analysis. Uterine weight and histology were also evaluated as additional internal oestrogen-sensitive controls. Rats on the soy-free diet had greater gains in body weight (259 +/- 6% baseline body weight) than rats on the soy-rich diet (238 +/- 4% baseline body weight). No differences were seen in uterine weight and histology, peri-ischaemic physiological parameters and infarct volumes between the treatment groups. The results of this pilot study suggest that the dietary soy level tested may not alter acute infarct volumes in ischaemic female rat brain. More studies addressing the potential confounding effects of dietary soy in 'oestrogen-sensitive' stroke models are needed if investigators are to make informed choices regarding diets used in experimental stroke research.

The effect of moderate hypothermia in acute ischemic stroke on pericyte migration: An ultrastructural study

Pericytes are essential components of the blood–brain barrier together with endothelial cells and astrocytes. Any disturbance of brain perfusion may result in blood–brain barrier dysfunction due to pericyte migration from the microvascular wall. The neuroprotective influence of hypothermia on ischemic brain injury has been clearly shown in models of both global and focal ischemia. Leakage of plasma proteins contributes to the extension of neuronal injury and hypothermia has a neuroprotective influence during the ischemic insult. This line of thinking impelled us to investigate the possible role of the pericytes in the occurrence of hypothermic protection during cerebral ischemia. In this study, we examined at the ultrastructural level the effect of moderate hypothermia on microvascular pericyte responses using a rat model of permanent middle cerebral artery occlusion. Twenty rats were divided into four groups. Middle cerebral artery occlusion was performed in all rats except the control group (first group), which was used to determine the pericyte morphology under normal conditions. In the second group, pericyte response to irreversible ischemia under normothermic conditions was examined at the end of the first hour. In the third group, pericyte response to hypoxia was examined under normothermic conditions three hours after ischemia. In the fourth group, temporalis muscle temperature was maintained at 27–29 °C for 1 h after middle cerebral artery occlusion and pericyte response was then examined at the ultrastructural level. In ischemic normothermic conditions at the end of the first hour (Group 2), a separation was observed between pericytes and the basement membrane and this was interpreted as pericyte migration from the microvascular wall. In ischemic normothermic conditions at the end of the third hour (Group 3), basement membrane disorganization and increased space between the basement membranes were seen in addition to the differentiation of second group. In ischemic hypothermic conditions at the end of the first hour (Group 4), pericyte separation or migration from basement membrane were not seen and the blood–brain barrier remained firm. These findings were interpreted by the authors as a possible relationship between pericyte behavior and neural protection during hypothermia. We suggest that hypothermia may delay the pericyte response but not necessarily attenuate it, and should be associated with hypothermic protection.

Moderate hypothermia, but not calpain inhibitor 2, attenuates the proteolysis of microtubule-associated protein 2 in the hippocampus following traumatic brain injury in rats

The degradation of the cytoskeletal protein microtubule-associated protein 2 (MAP2), by calpain has been known to occur following traumatic brain injury. We examined the therapeutic potential of calpain inhibitor 2, compared with that of moderate hypothermia in traumatic brain injury produced by weight drop in rats. An inhibitor treated group (n = 8) received calpain inhibitor 2 intravenously (i.v.) for 5 min before and for 6 h after injury (total 2 micromol); a hypothermic (HT) group (n = 8) was maintained at 30 degrees C (temporalis muscle temperature) for 45 min prior to and 60 min after injury; an untreated (UT) group (n = 8) received an infusion of inactive vehicle. Eight rats (sham group) underwent surgery without brain injury. Histopathological (haematoxylin and eosin staining) and MAP2 (immunohistchemistry and western blotting) evaluations were performed at 6 h after injury. Ipsilateral cortical damage was marked in the injured groups. In the hippocampus, marked pyramidal neuronal damage was observed in the UT and calpain inhibitor treated (CI) groups, while these neurons were better preserved in the HT group. The hippocampal MAP2 levels in the UT, CI and HT groups were significantly decreased to 13 +/- 9%, 28 +/- 33% and 62 +/- 25% of the sham contol, respectively. MAP2 concentration in the HT group was significantly higher than in UT and CI groups (P < 0.05). The results suggest that moderate hypothermia, but not calpain inhibitor 2 with the tested regime, attenuates cytoskeletal damage in the ipsilateral hippocampus at 6 h after traumatic brain injury.

Cochlear temperature correlates with both temporalis muscle and rectal temperatures. Application for testing the otoprotective effect of hypothermia

Conclusions. During systemic hypothermia, the internal temperature of the rat cochlea correlates best with the temporalis muscle and rectal temperatures. These positive correlations will be used in future studies to assess the efficacy of mild and moderate hypothermia to protect hearing against the progressive loss caused by electrode insertion in a clinically relevant model of cochlear implantation trauma. Objective. To monitor the internal temperature of the cochlea during induced systemic hypothermia using a reference tissue instead of an internal cochlear temperature probe. Material and methods. The temperatures of the cochlea, brain, temporalis muscle and rectum were determined during periods of normothermia (37°C), mild (33°C) and moderate (30°C) hypothermia and slow rewarming in anesthetized adult Fisher rats. These values were compared using statistical analysis to establish the best correlations between the temperature of the cochlea and the temperature at the three other temperature measurement sites. Results. The strongest correlations with the internal temperature of the cochlea during the induction of mild-to-moderate hypothermia were obtained for the temperatures of the ipsilateral temporalis muscle and rectum.

Selective Estrogen Receptor Modulator LY353381.HCl-Mediated Neuroprotection and BCL-2 Expression After Experimental Stroke

62 Estrogen replacement in ovariectomized rats reduces cerebral tissue infarction sustained after experimental stroke. We hypothesized that LY353381.HCl, a selective estrogen receptor modulator (SERM), reduces cerebral tissue infarction after middle cerebral artery occlusion (MCAO), and that the mechanism of protection is not related to preservation of blood flow. After 5–9 days of treatment with LY353381.HCl (LY) or vehicle (VEH), ovariectomized rats were subjected to 2 hours of MCAO under halothane anesthesia, followed by 22 hours of recovery. Ischemia was confirmed by laser-Doppler flowmetry. MAP, blood gases, and rectal and temporalis muscle temperature were controlled. Infarct volumes were measured by 2,3,5-triphenyltetrazolium chloride (TTC) staining and digital image analysis. Ovariectomized (OVX) rats treated with LY (n=16) had smaller infarct volumes in the caudoputamen (CP) than VEH (n=14) treated rats, 49%±6% vs. 64%±4% of ipsilateral CP, respectively, P &lt;0.05. Cerebral cortical (CTX) infarct size was not statistically different between treatment groups (7%±3% vs. 13%±4% for LY vs. VEH, respectively). In a second cohort of OVX rats, end ischemic regional cerebral blood flow (CBF) was measured by 14 C-iodoantipyrine autoradiography in LY (n=4) and VEH (n=3) treated rats. Absolute ischemic CBF and tissue volume distribution to low flow zones were similar in both groups. In a final cohort, 22 hours post MCAO, tissue was sampled from representative regions of CTX and CP in OVX (n=5) and LY (n=4) treated groups and analyzed for BCL-2 mRNA expression using ribonuclease protection assay. LY increased BCL-2 mRNA in both ipsilateral CTX and CP. We conclude that LY353381.HCl confers protection from focal cerebral ischemia by mechanisms that are not related to CBF but may involve increased BCL-2 expression.

The Effect of the Dendritic Growth Factor BMP-7 on Local Cerebral Glucose Utilization and Blood Flow in Reversible Middle Cerebral Artery Occlusion in Rats

P79 Bone morphogenetic protein-7 (BMP-7) (=osteogenic protein-1, OP-1) has been shown to enhance dendritic growth and improve functional recovery after experimental stroke. In this study, we examined the effect of BMP-7 on local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCMRglu) following transient middle cerebral artery occlusion. Sprague Dawley rats (n=29) were anesthetized with halothane/nitrous oxide and received 2-h middle cerebral artery occlusion (MCAo) by poly-L-lysine coated intraluminal suture (1). Rectal and cranial (left temporalis muscle) temperatures were regulated at 37–37.5 o C. BMP-7 or vehicle (volume, 25μl) was administered intracisternally in blinded fashion at 24h after MCAo. Neurological status was evaluated during occlusion (60 min) and daily for 2 days after MCAo; a grading scale of 0–12 was employed (1). LCMRglu was measured autoradiographically with 14 C-2 deoxyglucose (2-DG) and LCBF with 14 C-iodoantipyrine 48 h after MCAo. Four animals groups were studied: LCMRglu series (BMP-7, n=7; vehicle, n=8); LCBF series (BMP-7, n=6; vehicle, n=8). Average three-dimensional image data sets were constructed for each group and were compared by pixel-based statistical methods (2). Rectal and cranial temperatures, MABP, plasma glucose and blood gases were similar among groups. BMP-7 significantly improved the neurological score compared to vehicle at 48 after MCAo (7.3 ± 0.4 vs. 9.0 ± 0.2, respectively; p&lt;0.0003). Compared to vehicle-rats, BMP-7 significantly increased LCMRglu in ipsilateral basal ganglia, improved LCBF in ipsilateral subthalamus, and decreased LCBF and LCMRglu in contralateral cortical regions. The improved glucose metabolism in ipsilateral basal ganglia of BMP-7 rats is compatible with its salutary influence on neurological recovery. Supported by Creative BioMolecules, Inc., Hopkinton, MA, and by NIH Grant NS 05820. (1)Belayev L, Alonso OF, Busto R, Zhao W, Ginsberg MD: Stroke 27:1616–1623,1996. (2)Zhao W, Belayev L, Ginsberg MD: J Cereb Blood Flow Metab 17:1281–1290,1997.

LY353381.HCl, a selective estrogen receptor modulator, and experimental stroke.

The impact of postmenopausal estrogen replacement therapy on stroke prevention and stroke severity remains controversial. Previously we have shown that cerebral tissue infarction volume sustained after middle cerebral artery (MCA) occlusion is smaller in female than in male animals. This protection is lost after ovariectomy but is restored by 17ss-estradiol replacement. However, the therapeutic range for estradiol is suboptimal, since only doses resulting in a narrow range of plasma levels are protective in brain. The present study tested the hypothesis that a benzothiophene analogue and selective estrogen receptor modulator, LY353381.HCl (LY), reduces tissue infarction after MCA occlusion in estrogen-deficient, ovariectomized female rats. Ovariectomized female Wistar rats received LY 10 mg/kg (n=16) or an equivalent volume of vehicle (n=14) by gavage for 5 to 8 days. Subsequently, each animal was anesthetized with halothane (1.2%) and treated with 2 hours of MCA occlusion by the intraluminal filament technique and 22 hours of recovery. Infarction volumes in the cerebral cortex and caudoputamen were determined by 2, 3,5-triphenyltetrazolium chloride staining and digital image analysis. End-ischemic regional cerebral blood flow (CBF) was measured in separate animal cohorts by quantitative [(14)C]iodoantipyrine autoradiography. Caudoputamen infarction was reduced by LY treatment (49+/-6% versus 64+/-4% of ipsilateral caudoputamen in LY and vehicle groups, respectively; P:<0.05). Cerebral cortical infarction was not different in the LY compared with vehicle group (7+/-3% versus 13+/-4% of ipsilateral cerebral cortex, respectively). Intra-ischemic blood pressure, arterial blood gases, and temporalis muscle temperature were controlled and equivalent between treatment groups. Averaged laser-Doppler flow during MCA occlusion was 36+/-3% of baseline in the LY group versus 29%+/-2% in the vehicle group. However, end-ischemic CBF or blood flow distribution within the MCA territory was not altered by LY treatment. Cortical or caudoputamen tissue volumes with end-ischemic CBF <20 mL/100 g per minute were similar in both groups. We conclude that LY confers neuroprotection from focal cerebral ischemia in caudoputamen in ovariectomized female rats. The mechanism of protection is not linked to preservation of ischemic cerebral blood flow, as determined by end-occlusion quantitative autoradiography.

The Effect of the Dendritic Growth Factor BMP-7 on Local Cerebral Glucose Utilization and Blood Flow in Reversible Middle Cerebral Artery Occlusion in Rats

P79 Bone morphogenetic protein-7 (BMP-7) (=osteogenic protein-1, OP-1) has been shown to enhance dendritic growth and improve functional recovery after experimental stroke. In this study, we examined the effect of BMP-7 on local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCMRglu) following transient middle cerebral artery occlusion. Sprague Dawley rats (n=29) were anesthetized with halothane/nitrous oxide and received 2-h middle cerebral artery occlusion (MCAo) by poly-L-lysine coated intraluminal suture (1). Rectal and cranial (left temporalis muscle) temperatures were regulated at 37–37.5oC. BMP-7 or vehicle (volume, 25μl) was administered intracisternally in blinded fashion at 24h after MCAo. Neurological status was evaluated during occlusion (60 min) and daily for 2 days after MCAo; a grading scale of 0–12 was employed (1). LCMRglu was measured autoradiographically with 14C-2 deoxyglucose (2-DG) and LCBF with 14C-iodoantipyrine 48 h after MCAo. Four animals groups were studied: LCMRglu series (BMP-7, n=7; vehicle, n=8); LCBF series (BMP-7, n=6; vehicle, n=8). Average three-dimensional image data sets were constructed for each group and were compared by pixel-based statistical methods (2). Rectal and cranial temperatures, MABP, plasma glucose and blood gases were similar among groups. BMP-7 significantly improved the neurological score compared to vehicle at 48 after MCAo (7.3 ± 0.4 vs. 9.0 ± 0.2, respectively; p<0.0003). Compared to vehicle-rats, BMP-7 significantly increased LCMRglu in ipsilateral basal ganglia, improved LCBF in ipsilateral subthalamus, and decreased LCBF and LCMRglu in contralateral cortical regions. The improved glucose metabolism in ipsilateral basal ganglia of BMP-7 rats is compatible with its salutary influence on neurological recovery. Supported by Creative BioMolecules, Inc., Hopkinton, MA, and by NIH Grant NS 05820. (1)Belayev L, Alonso OF, Busto R, Zhao W, Ginsberg MD: Stroke 27:1616–1623,1996. (2)Zhao W, Belayev L, Ginsberg MD: J Cereb Blood Flow Metab 17:1281–1290,1997.

Temperature and hemodynamic changes associated with increased neural damage to global hemispheric hypoxic ischemia by prior prostaglandin E2,D2and F2αadministration

Experiments compared the hemispheric neural damage resulting from global hemispheric hypoxic ischemia (GHHI, ligation of right common carotid artery plus 35min of 12% O2) in groups of anesthetized, male Long Evans rats, 9–10 weeks of age, kept at 37°C, and previously given an intracerebroventricular (i.c.v., 2.5μl) injection of 28 or 70 pmoles of PGE2, PGF2αor PGD2or sterile saline (SS) 30 min beforehand. Mean arterial pressure (MAP), ipsilateral cortical capillary blood flow (CBF), colonic (Tc), ipsilateral (Tipsi) and contralateral (Tcontra), temporalis muscle temperatures were measured before, during and for 15 min after GHHI. Necrotic neural damage was assessed 7 days post-GHHI. All groups given GHHI + PGs showed increased ipsilateral hemispheric damage to GHHI especially due to enhanced neocortical damage, compared to the saline control group given the same insult. PGD2was the most potent PG to cause further damage to the global insult. Tc, Tipsi, Tcontraand MAP increased following the i.c.v. injection of PGE2. Icv PGF2αtransiently decreased MAP, PGD2tended to decrease cerebral blood flow and neither evoked changes in temperature compared to respective pre-injection control values. Results demonstrate increased neural damage to GHHI with prior icv PGE2, PGF2αor PGD2administration.

The effect of mild hypothermia, mannitol and insulin-induced hypoglycaemia on ischaemic infarct volume in the early period after permanent middle cerebral artery occlusion in the rat.

We investigated the effect of mild hypothermia (32-34 degrees C), mannitol and insulin - induced hypoglycaemia on the ischaemic infarct volume on permanent middle cerebral artery occlusion with bilateral carotid artery ligation in rats. Temporalis muscle temperature as an indicator of brain temperature was monitored throughout the experiment in all rats, which were randomly divided into seven groups. During ischaemia, control rats received intravenous saline in a normothermic condition; treated rats had hypothermia and intravenous saline, hypothermia and mannitol, normothermia and mannitol, normothermia and insulin, normothermia, insulin and glucose, and hypothermia and insulin applied. After the experiment, the animals were killed, and brain sections were stained with haematoxylin and eosin. Images of infarct areas were determined using a camera attached to the microscope, and analysed by image analysis software. The total volume of infarcted tissue, right hemispheric volume, and the percentage of infarction were determined at the end of the image analysis investigation. The infarct volume on the control group was found to be 128.16+/-6.67 mm(3). Infarct volumes in hypothermic groups were significantly smaller than those of the control group (p<0.05). There were no significant differences between infarct volumes in the hypothermic groups. However, we found that hypothermia plus mannitol have the greatest neuro-protective effect. In normothermic rats, the infarct volume decreased proportionally but not statistically (p>0.05) whether mannitol or insulin was given. Our results also demonstrate that pre-, and post-ischaemic serum glucose concentrations influence the volume of infarction. Rats that had had pre-ischaemic high serum glucose concentrations had a higher volume of infarct than the hypothermic rats (p<0.05), while rats with post-ischaemic low serum glucose concentrations had a lower volume of infarct than the control rats.

Posttraumatic hypothermia in the treatment of axonal damage in an animal model of traumatic axonal injury

Many investigators have demonstrated the protective effects of hypothermia following traumatic brain injury (TBI) in both animals and humans. Typically, this protection has been evaluated in relation to the preservation of neurons and/or the blunting of behavioral abnormalities. However, little consideration has been given to any potential protection afforded in regard to TBI-induced axonal injury, a feature of human TBI. In this study, the authors evaluated the protective effects of hypothermia on axonal injury after TBI in rats. Male Sprague-Dawley rats weighing 380 to 400 g were subjected to experimental TBI induced by an impact-acceleration device. These rats were subjected to hypothermia either before or after injury, with their temporalis muscle and rectal temperatures maintained at 32 degrees C for 1 hour. After this 1-hour period of hypothermia, rewarming to normothermic levels was accomplished over a 90-minute period. Twenty-four hours later, the animals were killed and semiserial sagittal sections of the brain were reacted for visualization of the amyloid precursor protein (APP), a marker of axonal injury. The density of APP-marked damaged axons within the corticospinal tract at the pontomedullary junction was calculated for each animal. In all hypothermic animals, a significant reduction in APP-marked damaged axonal density was found. In animals treated with preinjury, immediate postinjury, and delayed hypothermia, the density of damaged axons was dramatically reduced in comparison with the untreated controls (p < 0.05). The authors infer from these findings that early as well as delayed posttraumatic hypothermia results in substantial protection in TBI, at least in terms of the injured axons.

Effect of brain, body, and magnet bore temperatures on energy metabolism during global cerebral ischemia and reperfusion monitored by magnetic resonance spectroscopy in rats.

To record brain temperature for comparison with rectal and temporalis muscle temperatures in preliminary studies before MR spectroscopy experiments, a thermistor was inserted into the basal ganglia in eight anesthetized, ventilated, and physiologically monitored rats. The rats were placed in an MR spectrometer and subjected to 60 min of global cerebral ischemia and 2 h of reperfusion without radiofrequency (RF) pulsing. Body temperature was maintained at 37.5-38.0 degrees C (normothermia) or 36.5-37.0 degrees C (mild hypothermia). Brain temperature during ischemia, which dropped to 31.9 +/- 0.3 (hypothermia) and 33.6 +/- 0.5 degrees C (normothermia), correlated with temporalis muscle temperature (r2 = 0.92) but not with body or magnet bore temperature measurements. Ischemia reduced brain temperature approximately 1.7 degrees C in rats subjected to mild hypothermia (1 degree reduction of body temperature). Parallel MR spectroscopy experiments showed no significant difference in energy metabolites between normothermic and hypothermic rats during ischemia. However, the metabolic recovery was more extensive 20-60 min after the onset of reperfusion in hypothermic rats, although not thereafter (P < 0.05). Mild hypothermia speeds metabolic recovery temporarily during reperfusion but does not retard energy failure during global ischemia in rats.

Inhibition of nitric oxide synthase potentiates hypertension and increases mortality in traumatically brain-injured rats.

We examined the effects of N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), on mortality, morbidity, and cardiovascular parameters following traumatic brain injury (TBI) in the rat. Rats were anesthetized with 2% isoflurane prior to moderate (2.0 atmosphere), central fluid percussion TBI. Temporalis muscle temperature was maintained at 37 +/- 0.5 degrees C. L-NAME (10 mg/kg iv) was administered once at either 5 min before, 5 min after, or 15 min after TBI. Sensorimotor deficits and spatial learning/ memory deficits were assessed after injury. Separate groups of rats were monitored for cardiovascular parameters. Preinjury administration of L-NAME significantly increased mortality from 13 (vehicle) to 70% (associated with pulmonary edema), whereas postinjury, L-NAME had no effect on mortality (14 and 25%). L-NAME administered at 5 or 15 min after injury had no significant effect on motor performance or cognitive performance deficits associated with TBI. L-NAME in uninjured rats increased arterial blood pressure by 25 mmHg within 2 min. L-NAME injected 5 min before TBI greatly prolonged the hypertensive episode associated with TBI (1 min in vehicle vs 60 min in L-NAME). L-NAME injected 5 min after TBI caused a sustained 35 mmHg increase in blood pressure. These findings suggest that acute inhibition of NOS has detrimental consequences on mortality that may be owing to its cardiovascular effects.

Effect of hypothermia, dichloroacetate, and deferoxamine in the treatment for cortical edema and functional recovery after experimental cortical impact in the rat.

To investigate the effects of hypothermia alone or in combination with dichloroacetic acid (DCA) and/or deferoxamine (DFO) in reducing cortical edema (CE) and improving neurologic functional recovery after moderate closed and head trauma with controlled cortical impact (CCI). Anesthetized rats were randomized to receive right parietal moderate CCI (impact depth 2 mm, speed 3.5 m/sec) or sham operations. Immediately after trauma, the animals underwent selective brain cooling to 30 degrees C (temporalis muscle temperatures). Ten minutes after trauma, the randomized animals received intraperitoneal doses of DCA (25 mg/kg), DFO (50 mg/kg), both DCA and DFO, or equivolume normal saline. For evaluation of cortical edema, some animals (n = 42) were sacrificed 4 hours after trauma and cortical specific gravity (SpG) was determined gravimetrically. The other animals (n = 47) were evaluated for functional recovery beginning 6 days posttrauma. Neurobehavioral performance was assessed in the Morris water maze. Cortical edema was significantly less in the animals treated with hypothermia (SpG = 1.041 +/- 0.001, p < 0.05) compared with the untreated traumatized animals (SpG = 1.037 +/- 0.001). Combination treatment with hypothermia and drug treatment did not reduce cortical edema when compared with no treatment. Hypothermia with and without drug treatment did not improve neurobehavioral performance when compared with no treatment. In this pilot study with a relatively small sample size, hypothermia alone significantly reduced post-CCI cortical edema as measured by SpG. Hypothermia combined with drug treatment did not reduce posttraumatic cortical edema. Hypothermia with and without drug therapy did not improve functional neurologic recovery in the rats subjected to CCI.

Mild hypothermia fails to protect late hippocampal neuronal loss following forebrain cerebral ischaemia in rats.

Anaesthetized male rats (n = 86) from both Long-Evans strain (LES) (n = 43) and Wistar strain (WS) (n = 43) were utilized for the experiments. While three animals from each strain were used as control, 40 rats from each strain underwent up to 10 minutes forebrain ischaemia by bilateral common carotid artery (CCA) occlusion combined with systemic hypotension [Mean Arterial Blood Pressure (MABP) = 50 mm/Hg]. The animals from each strain were divided into four (n = 10) groups. In both strains, groups (n = 10) 1 and 2, temporalis muscle (TM) and body temperatures of the animals were kept at 36-37 degrees C during the experiments. The groups 1 and 2 were killed in 3 and 7 days after the ischaemic insult, respectively. The groups 3 and 4 were also killed 3 and 7 days after the ischaemic insult, but the forebrain ischaemia was carried out under mild cerebral hypothermia (TM temperature = 33 degrees C). Pyramidal neurons of the hippocampal CA1 region from each group was evaluated semiquantitatively. In WS, groups 1 and 2 showed moderate and severe neuronal loss in the CA1 region, respectively. However, in LES while the group 1 (3 days survival) did not show any neuronal loss, group 2 showed moderate neuronal loss of the CA1 region. While in group 3 (3 days survival, hypothermia) WS and LES, hypothermia protected the CA1 region, group 4 of LES showed mild neuronal loss. However WS, group 4 (7 days survival, hypothermia) showed severe neuronal loss of the CA1 region. It was concluded that mild hypothermia during ischaemic insults did not prevent the delayed postischaemic neuronal damage of the hippocampal CA1 region of both strains, and following 10 minutes forebrain ischaemia, male LES rats were found more resistant than male WS rats to neuronal loss of the CA1 region.

Therapeutic time window and dose response of the beneficial effects of ketamine in experimental head injury.

The aim of this study was to determine the time and dose response of the therapeutic effects of the N-methyl-D-aspartate receptor antagonist ketamine in experimental head injury. Sixty-six male Sprague-Dawley rats were divided into eight groups. Groups A, B, and C were surgically prepared but received no trauma. Groups D through H received a nonpenetrating impact to the left cranium. Group A (n = 7) received no treatment. Groups B (n = 4) and C (n = 5) received 60 and 120 mg/kg IP ketamine, respectively. Group D (n = 8) received no treatment. Groups E (n = 8) and F (n = 7) received 120 and 180 mg/kg IP ketamine, respectively, 1 hour after head trauma. Groups G (n = 7) and H (n = 9) were treated with 180 mg/kg IP ketamine 2 and 4 hours after head trauma, respectively. Neurological severity score (NSS, 0 through 25 from no injury to severe injury) was determined at 1, 24, and 48 hours after head trauma. After death at 48 hours, cortical slices were taken adjacent to the lesion on the traumatized hemisphere and from comparable sites in the contralateral hemisphere for determination of tissue specific gravity and water content. Brains were then placed in 4% formaldehyde, and the volume of hemorrhagic necrosis was measured 4 days later. NSS was compared within and between groups using the Kruskal-Wallis test for repeated measurements and Mann-Whitney U test for post hoc testing. Water content, specific gravity, and hemorrhagic necrosis were compared within and between groups using two-way ANOVA followed by Fisher's protected least significant difference procedure. A value of P < .05 was considered statistically significant. Head trauma alone increased NSS, decreased specific gravity, increased water content, and caused cerebral infarction in the injured hemisphere. Ketamine given in two time-dose regimens, 180 mg/kg IP at 2 hours (group G) and 120 mg/kg IP at 1 hour (group F) after trauma, improved NSS from 11.6 +/- 1.7 and 14.4 +/- 0.8 at 1 hour to 4.4 +/- 1.3 and 8.0 +/- 1.4 (mean +/- SEM) at 48 hours, respectively (P < .03). Compared with the untreated group (group D), 180 mg/kg IP ketamine given at 2 and 4 hours after head trauma decreased the volume of hemorrhagic necrosis from 37.1 +/- 9.5 mm3 to 10.1 +/- 3.8 and 15.3 +/- 3.6 mm3, respectively (P < .05). Brain tissue specific gravity and water content at 48 hours were not significantly different between treated and untreated groups. There was no difference in rectal and temporalis muscle temperature between groups. We conclude that 180 mg/kg IP ketamine was effective in ameliorating neurological dysfunction after head trauma in rats when the administration time was delayed for 1 hour to 2 hours but not after 4 hours. When given at 1 hour after head trauma, ketamine at 120 mg/kg but not 60 mg/kg is effective in reducing neurological damage after head trauma.

Ketamine alters calcium and magnesium in brain tissue following experimental head trauma in rats.

We previously reported that the N-methyl-D-aspartate receptor antagonists dizocilpine maleate and ketamine improved the neurological severity score (NSS) after head trauma in rats. Other investigators have reported increased calcium and decreased magnesium following head trauma in untreated rats. The present study was designed to determine whether ketamine influences the concentrations of calcium and magnesium in brain tissue following head trauma. Eighty-six male Sprague-Dawley rats (180 +/- 15 g) were divided into eight groups. Groups A (no head injury) and C (head injury) received no treatment. Groups B (no head injury) and D-H (head injury) received ketamine. In groups D, E, and F, ketamine, 180 mg/kg i.p., was given 1, 2, and 4 h after head trauma, respectively. In groups G and H, ketamine, 120 and 60 mg/kg, respectively, was given 1 h after head trauma. After we killed the rats at 48 h, cortical slices were taken to measure tissue calcium and magnesium content by the inductively coupled plasma atomic emission spectroscopy method. In the contused hemispheres, calcium increased and magnesium decreased (p < 0.0001). Among the head-injured groups, the increase in brain tissue calcium was smaller in groups receiving 60 mg/kg of ketamine at 1 h or 180 mg/kg of ketamine at 1, 2, or 4 h than in the group not receiving ketamine. The decrease in brain tissue magnesium was smaller in the groups receiving 180 mg/kg of ketamine at 1 and 2 h than in the group not receiving ketamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral Protection by Moderate Hypothermia Initiated After Experimental Traumatic Brain Injury

The effects of postinjury hypothermia on behavioral outcome following moderate fluid percussion traumatic brain injury (TBI) were examined. In Experiment I, three groups of rats were examined. The first group was normothermic (37.5 degrees C); and hypothermia (30 degrees C) was initiated 15 min and 30 min postinjury in the second and third groups, respectively. Whole body cooling was achieved by ventral ice pack. Cooling of the brain to 30 degrees C was achieved in 25 min and maintained for 60 min. Brain temperature was measured indirectly by a probe in the temporalis muscle. Behavioral outcome was assessed by beam-balance performance, beam-walking performance, and body weight loss measured daily for 5 days after TBI. Both the normothermic group and the 30-min postinjury hypothermic group exhibited significant (p < 0.05) beam-balance and beam-walking deficits on days 1 through 5 after TBI. In contrast, the 15-min postinjury hypothermic group exhibited significant (p < 0.05) beam-walking deficits only on day 1 after TBI and significant (p < 0.05) beam-balance deficits on days 1, 3, and 4 after TBI. In Experiment II, subcortical brain temperature was compared to temporalis muscle temperature in normothermic (37.5 degrees C) and hypothermic (30 degrees C) rats subjected to TBI. In both groups brain temperature tracked within 0.4 degree C of temporalis muscle temperature. These results are similar to post-TBI excitatory receptor antagonist studies and indicate a therapeutic window for moderate hypothermia of less than 30 min after moderate fluid percussion TBI in the rat.