Xylazine effects on opioid-induced brain hypoxia

RATIONALE

Xylazine has emerged in recent years as an adulterant in an increasing number of opioid-positive overdose deaths in the United States. Although its exact role in opioid-induced overdose deaths is largely unknown, xylazine is known to depress vital functions and cause hypotension, bradycardia, hypothermia, and respiratory depression.

OBJECTIVES

In this study, we examined the brain-specific hypothermic and hypoxic effects of xylazine and its mixtures with fentanyl and heroin in freely moving rats.

RESULTS

In the temperature experiment, we found that intravenous xylazine at low, human-relevant doses (0.33, 1.0, 3.0 mg/kg) dose-dependently decreases locomotor activity and induces modest but prolonged brain and body hypothermia. In the electrochemical experiment, we found that xylazine at the same doses dose-dependently decreases nucleus accumbens oxygenation. In contrast to relatively weak and prolonged decreases induced by xylazine, intravenous fentanyl (20 μg/kg) and heroin (600 μg/kg) induce stronger biphasic brain oxygen responses, with the initial rapid and strong decrease, resulting from respiratory depression, followed by a slower, more prolonged increase reflecting a post-hypoxic compensatory phase, with fentanyl acting much quicker than heroin. The xylazine-fentanyl mixture eliminated the hyperoxic phase of oxygen response and prolonged brain hypoxia, suggesting xylazine-induced attenuation of the brain's compensatory mechanisms to counteract brain hypoxia. The xylazine-heroin mixture strongly potentiated the initial oxygen decrease, and the pattern lacked the hyperoxic portion of the biphasic oxygen response, suggesting more robust and prolonged brain hypoxia.

CONCLUSIONS

These findings suggest that xylazine exacerbates the life-threatening effects of opioids, proposing worsened brain hypoxia as the mechanism contributing to xylazine-positive opioid-overdose deaths.

Basic metabolic and vascular effects of ketamine and its interaction with fentanyl

Ketamine is a short-acting general anesthetic with hallucinogenic, analgesic, and amnestic properties. In addition to its anesthetic use, ketamine is commonly abused in rave settings. While safe when used by medical professionals, uncontrolled recreational use of ketamine is dangerous, especially when mixed with other sedative drugs, including alcohol, benzodiazepines, and opioid drugs. Since synergistic antinociceptive interactions between opioids and ketamine were demonstrated in both preclinical and clinical studies, such an interaction could exist for the hypoxic effects of opioid drugs. Here, we focused on the basic physiological effects of ketamine as a recreational drug and its possible interactions with fentanyl-a highly potent opioid that induces strong respiratory depression and robust brain hypoxia. By using multi-site thermorecording in freely-moving rats, we showed that intravenous ketamine at a range of human relevant doses (3, 9, 27 mg/kg) dose-dependently increases locomotor activity and brain temperature, as assessed in the nucleus accumbens (NAc). By determining temperature differentials between the brain, temporal muscle, and skin, we showed that the brain hyperthermic effect of ketamine results from increased intracerebral heat production, an index of metabolic neural activation, and decreased heat loss due to peripheral vasoconstriction. By using oxygen sensors coupled with high-speed amperometry we showed that ketamine at the same doses increases NAc oxygen levels. Finally, co-administration of ketamine with intravenous fentanyl results in modest enhancement of fentanyl-induced brain hypoxia also enhancing the post-hypoxic oxygen increase. Therefore, in contrast to fentanyl, ketamine increases brain oxygenation but potentiates brain hypoxia induced by fentanyl.

[Delayed posthypoxic leucoencephalopathy after suicide attempt with opioids]

Delayed posthypoxic leucoencephalopathy (DPHL) is a rare condition with manifestation of neurological and neuropsychological symptoms, following an acute hypoxic condition with an intermittent recovery period of four weeks. MRI findings show symmetric subcortical white matter lesions. We present a patient admitted with symptoms and brain MRI-scan consistent with DPHL. Four weeks prior the patient had tried to commit suicide with opioids. DPHL should be considered in patients with subacute onset of neurological and neuropsychological symptoms after an acute hypoxic condition of the brain.

Optimal dosages of fluoxetine in the treatment of hypoxic brain injury induced by 3-nitropropionic acid: implications for the adjunctive treatment of patients after acute ischemic stroke

AIM

The serotonin selective reuptake inhibitor fluoxetine (Flx) has tried to treat patients suffered acute ischemic stroke because of its possible neuroprotective actions. However, besides the neuroprotective effect, Flx at high concentration also induces some actions in contradiction to neuroprotection in the brain. The purpose of this study was to investigate whether Flx presents neuroprotective effect against 3-nitropropionic acid (3-NP)-induced hypoxic brain injury, and what is the most suitable dosage of Flx.

METHODS

Mouse model was established by subacute systemic administration of 3-NP. Rotarod and pole tests were used to evaluate motor deficit. The oxidative stress and oxidative DNA damage were assessed respectively by measuring malondialdehyde and 8-hydroxydeoxyguanosine content in brain homogenates.

RESULTS

According to measurements in the rotarod test, 7 days pretreatment plus 5 days treatment of Flx at low (2.5 mg/kg/day) and, to a lesser degree, medium (5 mg/kg/day) doses exerted a rapid and strong protection against the neurotoxicity induced by 3-NP, whereas Flx at high dose (10mg/kg/day) showed a much late and light effect. Similarly, in the pole test, Flx at 2.5 mg/kg/day had the strongest protective effects. Again, only Flx administration at 2.5 mg/kg/day canceled out the enhancement of malondialdehyde and 8-hydroxydeoxyguanosine in striatum following 3-NP neurotoxication.

CONCLUSIONS

Flx attenuated the motor deficits induced by 3-NP in a dose-dependent manner. In contrary to the high dose, Flx at the lower doses had a more remarkable effect against 3-NP insult, similar to acute ischemic stroke.

[Immune system disorders and their correction in critically ill patients with toxic and hypoxic encephalopathy]

In this article there are materials, which were received in the process of treatment of 69 patients with azaleptin (leponeks) acute severe poisonings. The immunologic research has shown that the first phase of acute poisonings in patients with toxicohypoxic encephalopathy is accompanied by severe immune alterations. The alterations of proinflammation and antiinflammation cytokines have been investigated and its increase has not been revealed. It was shown, that the employment of citoflavin in intensive therapy of acute poisonings leads to decrease of the level of immunosupression.

[Methods for the prevention and treatment of toxico-hypoxic encephalopathy in patients with acute severe poisoning]

The study included 147 patients with toxico-hypoxic encephalopathy resulting from acute poisoning. It was shown that intensive therapy with cytoflavin (20 ml in 400 ml of 5% glucose solution twice daily for 7 days) reduced severity of hypoxic brain lesions and suppression of CNS as apparent from the improvement of its bioelectric activity. The recovery of CNS regulatory action on the life-sustaining systems of the body promoted normalization of the respiratory component of oxygen transport. The improvement of the patients' conditions in the acute phase contributed to accelerated recovery of cognitive-amnestic functions and social adaptation. Cytoflavin therapy improved the clinical picture of toxico-hypoxic encephalopathy due to the reduction in the duration of the comatose state from 45.3 +/- 8.2 to 27.7 +/- 6.9 hr and the decrease in the frequency of secondary pulmonary complications from 72.7 to 35.9%.

The effects of hypoxia on growth cones in the ovine fetal brain

OBJECTIVE

This study was designed to investigate the effects of hypoxia on neural process proliferation by studying its effects on growth cone tubulin and insulin-like growth factor (IGF)-I receptor content.

METHODS

Six fetal lambs were catheterized in the brachial artery and vein. Maternal oxygenation was reduced in steps from a fractional inspired oxygen concentration (FiO2) of 20% to 6% by addition of nitrogen to the inhaled gas mixture for a period of 4 h of reduced oxygen intake. Fetal arterial blood was sampled after the maternal FiO2 and oxygen were stable for >5 min at maternal FiO2 of 20% to 6%. Controls were obtained from normoxic fetuses whose ewes had similar surgery and were kept at an FiO2 of 20% throughout the experiment. Growth cones were isolated from the fetal cerebrum and cerebellum. alpha-tubulin and IGF-I receptors were quantified by immunoblotting. Tubulin and IGF-I receptor mRNA expressions were quantified by real-time polymerase chain reaction.

RESULTS

Maternal nitrogen breathing reduced fetal arterial pH from 7.32+/-0.06 to 6.99+/-0.02 (p<0.001). Hypoxia increased IGF-I receptors from 143+/-10 to 327+/-14 (p<0.001) and from 272+/-26 to 396+/-34 (p<0.001) fluorescence units/microg protein in the cerebrum and cerebellum, respectively. It also increased alpha-tubulin from 713+/-30 to 1873+/-126 (p<0.001) and from 780+/-34 to 2362+/-79 (p<0.001) fluorescence units/microg protein in the cerebrum and cerebellum, respectively. Expression of IGF-I receptor mRNA increased significantly in the hypoxic animals both in the cerebrum and the cerebellum, but there was no change in expression of alpha-tubulin mRNA.

CONCLUSIONS

This increase in IGF-I receptor expression and growth cone content may be an adaptive response to hypoxia to maintain neurite growth by facilitating binding of IGF-I. Hypoxia also increased the growth cone level of alpha-tubulin but did not increase its mRNA expression, which may indicate an inability to polymerize tubulin and build microtubules.

A case of fatal caffeine poisoning

Caffeine is a natural alkaloid methylxanthine that is found in various plants such as coffee or tea. Symptoms of a severe overdose may present with hypokalemia, hyponatremia, ventricular arrhythmias, hypertension followed by hypotension, respiratory failure, seizures, rhabdomyolysis, ventricular fibrillation and finally circulatory collapse. A 21-year-old woman called for the ambulance herself soon after the ingestion of about 10,000 mg of caffeine. At the arrival of the ambulance, the patient went into cardiac arrest almost immediately. After a total resuscitation period of 34 min including seven counter-shocks and 2 mg epinephrine, the patient was stable enough to be transferred to the hospital. The patient soon went into VF again and received two more counter-shocks and 1 mg epinephrine and finally an intravenous bolus dose of 300 mg amiodarone. The initial arterial blood gas showed pH at 6.47, lactate at 33 mmol/l and potassium level at 2.3 mmol/l. Unfortunately, no blood samples for caffeine analysis were taken. Three days after hospital admission, the patient developed myoclonus, which did not respond to medical treatment. Excessive intake of caffeine may produce arrhythmias and pronounced hypokalemia and ensuing ventricular fibrillation. In case of counter-shock-resistant VF, it can be necessary to give an early loading dose of amiodarone. Furthermore, it may be beneficial to replace the potassium as early as possible. Epinephrine and buffer solutions used during resuscitation may further decrease blood potassium levels and should be administrated cautiously. Epinephrine can be replaced by other vasopressor drugs, such as vasopressin without effects on beta-receptors.

Acute hydrogen sulfide poisoning in a dairy farmer

INTRODUCTION. Hydrogen sulfide is a lipid-soluble gas produced in occupational settings and from decaying organic matter. We present a 36-year-old man who developed acute respiratory arrest from hydrogen sulfide poisoning while performing work as a dairy farmer.

CASE REPORT

The subject entered a poorly ventilated tank containing degrading eggs and, within seconds, collapsed. Coworkers were able to extract him within minutes but he was apneic. He was intubated by emergency medical services and subsequently managed with supportive care in the intensive care unit. Upon admission, a powerful rotten egg scent was noted and a hydrogen sulfide poisoning was suspected. Serum analysis for the presence of thiosulfate confirmed the diagnosis. Nitrite therapy was not administered as the subject arrived outside of the therapeutic window of effectiveness and showed evidence of excellent oxygenation. His examinations following arrival were consistent with an anoxic brain injury which slowly improved several months after the incident with intensive neuro-rehabilitation.

DISCUSSION

Hydrogen sulfide is a mitochondrial toxin and inhibits cytochrome-aa(3) and prevents cellular aerobic metabolism. Therapies for toxic exposures include removal from the contaminated environment, ventilation with 100% oxygen, and nitrite therapy if administered immediately after exposure. Hyperbaric oxygen (HBO) therapy has anecdotal support and remains controversial.

CONCLUSION

Hydrogen sulfide is a significant occupational health hazard. Education, personal protective equipment, and early treatment are important in improving outcomes.

Carbon monoxide intoxication: an updated review

Carbon monoxide (CO), a highly toxic gas produced by incomplete combustion of hydrocarbons, is a relatively common cause of human injury. Human toxicity is often overlooked because CO is tasteless and odorless and its clinical symptoms and signs are non specific. The brain and the heart may be severely affected after CO exposure with carboxyhemoglobin (COHb) levels exceeding 20%. Damage occurs because the affinity of hemoglobin for CO is 210 times higher than for O(2). Hypoxic brain damage predominates in the cerebral cortex, cerebral white matter and basal ganglia, especially in the globus pallidus. Diagnosis requires clinical acumen and a high index of suspicion, combined with epidemiological data, clinical examination, analysis of ambient air CO and patient COHb levels; also required are cardiology evaluation including ECG as well as neurological evaluation including brain imaging (CT and/or MRI, MR spectroscopy), and neuropsychological testing. Although immediate O(2) breathing is sometimes an adequate treatment, hyperbaric oxygen therapy (HBO) is favored. Subsequently, only symptomatic therapy is available for the long-term sequelae of CO poisoning.

Effects of galantamine and donepezil on active and passive avoidance tests in rats with induced hypoxia

The cholinergic system undergoes changes with aging and in Alzheimer's disease. The effects of the anticholinesterase drugs galantamine and donepezil were studied in a model with sodium nitrite-induced hypoxia in rats. The animals were trained in the shuttle-box active avoidance test and in step-through and step-down passive avoidance tests. In the active avoidance test, hypoxic rats showed a decrease in the number of avoidances in the learning session and in retention. The hypoxic rats receiving galantamine showed an increase in the number of avoidances during the learning session. The groups in hypoxia treated with donepezil had an increased number of avoidances in the learning session. In memory retention tests, significant differences were not observed in the hypoxic animals treated with galantamine or donepezil. In the step-through passive avoidance test, rats treated with galantamine had no change in the latency of reactions during the learning session and memory retention tests. In the step-down passive avoidance test, the animals treated with galantamine had increase latency of reactions during the learning and short- or long-memory retention tests. The hypoxic rats receiving donepezil had increased latency of reactions in the step-down short memory retention test. Our results suggest that galantamine and donepezil improve cognitive functions in a model of hypoxia.

Drug-induced methaemoglobinaemia following elective coronary artery bypass grafting

Dapsone can alter the oxygen carrying capacity of haemoglobin. Some patients are more susceptible to these effects because of genetic factors, comorbidities or peri-operative factors such as anaemia. We present a 57-year-old lady who underwent elective coronary artery bypass grafting. Deterioration in neurological and respiratory condition prompted a review of her drug treatment. A combination of long-term dapsone therapy, co-existing cardiac and respiratory disease, postoperative anaemia and renal impairment contributed to her decompensation, despite a relatively low level of methaemoglobin. Successful management included stopping dapsone therapy, supportive care and administration of ascorbic acid.

Ginkgolides protect primary cortical neurons from potassium cyanide-induced hypoxic injury

In this study, we investigated the effects of ginkgolides (Gins A, B, C and J), the main constituent of the non-flavone fraction of EGb 761, on hypoxic injury induced by potassium cyanide (KCN) in primary cortical neurons. The neurons were pretreated with or without ginkgolides for 24 h before incubation with KCN for 4 h. Cell viability was then determined by a MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyletrazolium bromide] assay and lactate dehydrogenase (LDH) release from neurons into the medium was measured. The morphological changes of neurons were observed under inverse microscopy and electron microscopy. The results demonstrated that KCN (0.05 mmol/l) significantly decreased cell viability and increased LDH release (P < 0.05 versus the control). The characteristic changes of neuronal morphology induced by KCN were observed. However, pretreatment of neurons with 37.5 microg/ml of ginkgolides (ginkgolides + KCN group) led to a significant increase in cell viability, a decrease in LDH release (P < 0.05 versus the KCN group) and a remarkable improvement in cellular morphology in hypoxic neurons compared with the KCN group. The data suggested that ginkgolides have a significant role to protect the primary cortical neurons from hypoxic injury induced by KCN.

Fatality after a single dermal application of lindane lotion

Lindane lotion, approved by the US Food and Drug Administration (FDA) for treatment of scabies and lice, poses risks of serious adverse effects on the nervous system. In 2003, the FDA issued a public health advisory for lindane products, emphasizing the importance of compliance with labeling instructions. The author presents a case in which a fatal outcome followed a single dermal application of lindane. The product was not applied according to the labeling instructions, and the 66-year-old man rapidly developed hypoxemia, seizures, respiratory acidosis, and hypotension. The final diagnosis at autopsy was hypoxic ischemic encephalopathy from lindane. This case is consistent with other reports of severe neurological outcomes from pharmaceutical use of lindane. These factors suggest a need for the FDA to reassess whether the risks of lindane have been effectively communicated to healthcare providers.

Reversible delayed posthypoxic leukoencephalopathy

Hypoxic ischemic encephalopathy may cause early deep white matter abnormalities on MR imaging that usually progress to include gray matter and basal ganglia change. Toxic leukoencephalopathy due to heroin inhalation predominantly causes cerebellar and posterior cerebral radiologic change. Both conditions rarely present clinically and radiologically in a delayed manner with subsequent recovery. We report a case of reversible delayed posthypoxic/toxic leukoencephalopathy with no clinical or radiologic evidence of gray matter insult.

[The specific features of the development and course of toxicohypoxic encephalopathy in acute poisoning by neurotoxic agents]

The time course of changes in the development of toxicohypoxic encephalopathy in acute poisoning by neurotoxic agents was studied. Programmed treatment using efferent detoxifying, physio- and chemohemotherapy, and hyperbaric oxygenation and cytoflavin was proposed.

[Laboratory changes in exo- and endotoxemia in toxicohypoxic encephalopathy occurring with acute poisoning by psychopharmacological agents]

Examinations of patients with acute oral poisoning by psychotropic agents have indicated that toxicohypoxic encephalopathy develops, when the high concentrations of toxicants and their active metabolites specifically affect brain structures, resulting in oxidative stress and impaired natural detoxification mechanisms.

[Ischemic preconditioning in the brain]

Stroke-related death is the third most common cause of mortality in Hungary after cardiovascular diseases and cancer. In addition to the unfavourable mortality figures, the consequent development of neurological and psychiatric disorders in stroke patients imposes an enormous burden on the health care system and on the families. Numerous studies are being conducted world wide on the prevention of stroke and other cerebrovascular disorders like chronic hypoperfusion, as well as on acute stroke management and patient rehabilitation issues. As a result, our understanding of the mechanism of hypoxic brain damage steadily increased over the past years and decades which brought along promising achievements both in the field of stroke prevention and therapy. However, these broad-spectrum approaches also made clear that preventing neuronal death and thus reducing neurological damage are complex tasks that cannot be successfully resolved by targeting single mechanisms. Therefore, the development of alternative new drugs and clinically applicable complex neuroprotective strategies is warranted. One of the most promising approaches is to create ischemic tolerance in the brain by using pharmacological preconditioning paradigms. These drugs trigger similar events to those initiated by brief ischemic insults that later can make the cerebral tissue resistant to subsequent otherwise lethal stress (ischemic preconditioning).

[Effect of high-oxygen water on enhancing anoxia endurance and anti-fatigue function and the possible mechanism]

OBJECTIVE

To investigate the effect of high-oxygen water on anoxia endurance and anti-fatigue function in mice and explore the possible mechanism.

METHODS

KM mice were used. Their body weight, serum urea nitrogen, hepatic glycogen, swimming-sustaining time of mice with a load, plasma lactic acid content, survival time under anoxia or sodium nitrite poisoning were measured.

RESULTS

It was found that high-oxygen water can prolong swimming time and can protract the anoxia survival time of mice under normal pressure and being afflicted with acute cerebral ischemia (P<0.05). It can also decrease the level of serum urea nitrogen after exercise (P<0.05) and increase hepatic glycogen storage (P<0.05).

CONCLUSION

The results demonstrate that high-oxygen water can enhance the emergent survival ability of mice, the ability of fatigue recovery and anoxia endurance function. It also can increase the energy storage.

Cocaine induces apoptosis in cerebral vascular muscle cells: potential roles in strokes and brain damage

Cocaine abuse is known to induce different types of brain-microvascular damage and many adverse cerebrovascular effects, including cerebral vasculitis, intracranial hemorrhage, cerebral infarction and stroke. A major physiological event leading to these pathophysiological actions of cocaine could be apoptosis. Whether cocaine can cause brain-microvascular pathology and vascular toxicity by inducing apoptosis of cerebral vascular smooth muscle cells is not known. This study, using several different methods to discern apoptosis, was designed to investigate if primary cultured canine cerebral vascular smooth muscle cells can undergo apoptosis when treated with cocaine. After treatment with cocaine (10(-6)-10(-3) M) for 12-24 h, the death rates of cerebral vascular smooth muscle cells increased in a concentration-dependent manner compared with controls. Morphological analysis of cerebral vascular smooth muscle cells using confocal fluoresence microscopy showed that the percentage of apoptotic cerebral vascular smooth muscle cells increased after cocaine (10(-6)-10(-3) M) treatment in a concentration-dependent manner. TUNEL assays also showed positive results for cerebral vascular smooth muscle cells treated with cocaine. These results clearly demonstrate that cerebral vascular smooth muscle cells can undergo rapid apoptosis in response to cocaine in a concentration-dependent manner. Cocaine-induced apoptosis may thus play a major role in brain-microvascular damage, cerebral vascular toxicity and strokes.

Catastrophic brain injury after nicotine insecticide ingestion

Much attention has been paid to the long-term toxic and carcinogenic effects of nicotine-containing substances, particularly tobacco. Although rare, acute ingestions of large amounts of nicotine can produce rapid and dramatic toxicity. We present a case of an ingestion of a nicotine sulfate solution by a 15-year-old boy resulting in hypoxia and irreversible encephalopathy. The diagnosis of acute nicotine toxicity potentially could be delayed due to the fact that nicotine and cotinine are so commonly found on drug screens that they are considered "normal variants."

Successful transplantation of donor organs from a hemlock poisoning victim

BACKGROUND

The poison hemlock plant (Conium maculatum) has been a known poison since early in human history, most notably as the agent used for the execution/suicide of Socrates in ancient Greece. No experience has been reported regarding the suitability of a hemlock victim's organs for transplantation.

METHODS AND RESULTS

This report documents successful transplantation of the liver, kidney, and pancreas from a 14-year-old girl who died of anoxic encephalopathy from asphyxia after the accidental ingestion of fresh hemlock while on a nature hike. Predonation laboratory values were not remarkable, and liver and kidney biopsy results were normal. All organs in the three recipients had immediate function, and no recipient had any clinical evidence of transmitted toxin. All recipients are well, with functioning transplants at greater than 6 months after transplantation.

CONCLUSIONS

Poison hemlock intoxication does not seem to be a contraindication to organ donation.

Binge ethanol treatment causes greater brain damage in alcohol-preferring P rats than in alcohol-nonpreferring NP rats

BACKGROUND

Genetics is a known risk factor for alcoholism, and human alcoholics are known to suffer from a loss of brain function and mass. A 4 day rat binge drinking model is known to cause brain region-specific damage. To investigate the role of genetics in binge-drinking-induced brain damage, we studied bidirectionally selected rat lines, the alcohol-preferring P and the alcohol-nonpreferring NP rat lines.

METHOD

P and NP rats were treated with a 4 day binge ethanol protocol. Animals were killed, transcardially perfused, and fixed, and their brains were removed, sectioned, and stained by using the amino cupric silver stain of de Olmos or by using immunohistochemistry for phospho-extracellular signal regulated kinases and other antigens.

RESULTS

Significant brain damage was found in the olfactory bulbs, posterior perirhinal cortex, and entorhinal cortex in both P and NP rats. P rats were found to have significantly greater brain damage, compared with NP rats, in the posterior perirhinal and posterior entorhinal cortexes, 239% +/- 50% (p < 0.02) and 219% +/- 46% (p < 0.01), respectively. Phospho-extracellular signal regulated kinase immunohistochemistry stained prominently in damaged brain areas.

CONCLUSIONS

The P rat line, a genetic model of alcoholism, shows greater region-specific brain damage due to binge ethanol treatment than its genetic counterpart, the NP rat line. These findings suggest that genetics contribute to susceptibility for binge-induced brain damage.

Long-term neurobehavioral and histological damage in brain of mice induced by L-cysteine

We investigated whether structural central neural damage and long-term neurobehavioral deficits after L-cysteine (L-Cys) administration in mice is caused by hypoglycemia. Neonatal ICR mice were injected subcutaneously with L-Cys (0.5-1.5 mg/g body weight [BW]) or saline (control). Blood glucose was measured. At 50 days of age, mice were introduced individually into an eight-arm maze for evaluation of spatial memory (hippocampal-related behavior). Times for visiting all eight arms and number of entries until completion of the eight-arm visits (maze criteria) were measured. The test was repeated once daily for 5 days. In situ terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay was used for detection of brain damage. As early as 20 min and up to 2 h postinjection, animals treated with L-Cys doses higher than 1.2 mg/g BW developed hypoglycemia and looked ill. Several animals convulsed. Long-term survivors required more time, in a dose-dependent manner, to assimilate the structure of the maze, and animals treated with L-Cys (1.5 mg/g BW) exhibited TUNEL-positive changes in the hippocampal regions. All these changes were reversible by coadministration of glucose. We conclude that L-Cys injection can cause pronounced hypoglycemia associated with long-term neurobehavioral changes and central neural damage in mice. Since L-Cys is chemically different from the other excitatory amino acids (glutamate and aspartate), the long-reported L-Cys-mediated neurotoxicity may be connected to its hypoglycemic effect.

Differential regulation of 5' splice variants of the glutamate transporter EAAT2 in an in vivo model of chemical hypoxia induced by 3-nitropropionic acid

Defective glutamate uptake has been implicated as a pathogenic event of neuronal damage related to cerebral ischemia and hypoxia. In several models of ischemia-hypoxia, a reduced immunoreactivity and altered RNA expression of excitatory amino acid transporter 2 (EAAT2), the major excitatory amino acid transporter, have been reported. However, the gene regulation of EAAT2 under these conditions is incompletely understood. In this study, we investigated alternative splicing of EAAT2 in an in vivo mouse model of chemical hypoxia as induced by 3-nitropropionic acid (3-NP). The neurotoxin 3-NP is an inhibitor of mitochondrial energy production. Furthermore, it is known to inhibit glutamate reuptake directly, representing at least one of the mechanisms responsible for 3-NP-induced neurodegeneration. Here we report an expression analysis of five known (mEAAT2/5UT1-5) and two novel (mEAAT2/5UT6, -7) 5' splice variants of EAAT2 using semiquantitative PCR. The RNA expression was studied at 2, 12, 24, 48, and 72 hr and 7 days after 3-NP administration. mEAAT2/5UT4 and mEAAT2/5UT5 were up-regulated in the frontal cortex and down-regulated in the hippocampus 12-72 hr after chemical hypoxia. In the cerebellum, there was an increased expression of mEAAT2/5UT4 and a down-regulation of mEAAT2/5UT5. mEAAT2/5UT3 show a different regional expression pattern, being regulated in the cerebellum only. mEAAT2/5UT1-7 encoded distinct 5' regulatory sequences, including conserved elements of translational control. It is easily conceivable that expression alterations of 5' splice variants of EAAT2 are related to glutamate transporter malfunction after chemical hypoxia. Our findings contribute to the hypothesis that RNA splicing events can serve as a molecular mechanism of posthypoxic gene regulation.

Male and female sensitivity to alcohol-induced brain damage

Women are more vulnerable than men to many of the medical consequences of alcohol use. Although research has shown that male alcoholics generally have smaller brain volumes than nonalcoholic males, the few studies that have compared brain structure in alcoholic men and women have had mixed results. To adequately compare brain damage between alcoholic women and men, it is necessary to control for age and to have separate control groups of nonalcoholic men and women. Although the majority of studies suggest that women are more vulnerable to alcohol-induced brain damage than men, the evidence remains inconclusive.

Blood flow and ionic responses in the awake brain due to carbon monoxide

This study examined the effect of 2000 ppm CO on the brain of an awake rat. Measurements of regional perfusion as well as metabolic, ionic and electrical activities were used to examine whether mechanisms responsible for changes in brain perfusion were separable from those attributable to compromises in neuronal metabolism. Exposure to 2000 ppm CO resulted in elevation of cerebral blood flow. The stability of mitochondrial NADH redox level during CO exposure indicated that tissue hypoxia did not develop. The elevation in blood flow was inhibited by L-nitroarginine methyl ester, indicating that nitric oxide was responsible for the CO-induced elevation in blood flow. Exposure to 2000 ppm CO also triggered a significant decrease in pH and rise in extracellular potassium ion, possibly due to ion-pump inhibition. The amplitude of the electrocorticogram wave activity decreased, indicative of a compromise to physiological activity. These changes were not observed in rats anesthetized with pentobarbital during CO exposure, although anesthesia had no effect on the CO-induced elevation in blood flow and there was still no change in mitochondrial NADH redox level. We concluded that CO acts by separate mechanisms to alter cerebral vasoactivity and neuronal metabolic responses and that both processes are independent of hypoxic stress.

Complex partial status epilepticus induced by a microinjection of kainic acid into unilateral amygdala in dogs and its brain damage

OBJECTIVE

In order to investigate kainic acid (KA)-induced amygdaloid seizure and seizure-induced brain damage in dogs, and to compare these findings with that in other species, a KA-induced seizure model in dogs was produced.

MATERIAL AND METHODS

Normal beagle dogs were used. A Teflon cannula for KA injection was inserted into the left amygdala, and cortical or depth electrodes were positioned. One week after surgery, 1.5 microg of KA was microinjected into the left amygdala. EEGs and the behavior of the animals were monitored for 2 months after KA injection. In addition, neuron-specific enolase levels in the cerebrospinal fluid (CSF-NSE) were measured intermittently. At 2 months after the injection, histopathological studies were performed.

RESULTS

KA-treated dogs showed limbic seizures that started from the left amygdala within 30 min after injection. The seizures developed into complex partial status epilepticus (CPSE), and started independently from the bilateral amygdala during the CPSE. The CPSE lasted for 1-3 days, and the animals showed no spontaneous seizures during the 2-month observation period. A significant increase in CSF-NSE was observed immediately after CPSE. Histopathologically, extensive necrosis, which formed large cavity lesions, was observed around the bilateral amygdala.

SUMMARY

A microinjection of KA into unilateral amygdala in dogs induced CPSE. The seizures elicited independently from bilateral amygdala, and bilateral limbic structures suffered extensive injury. In addition, CSF-NSE was demonstrated as a useful marker of acute neuronal damage.

Fatal anaphylactoid reaction to N-acetylcysteine: caution in patients with asthma

Paracetamol overdose is a common reason for presentation to the emergency department and N-acetylcysteine is frequently used in the treatment of toxic paracetamol ingestions. Adverse reactions to N-acetylcysteine are common though usually mild and easily treated. Serious reactions to N-acetylcysteine however, are rare and there have been no previous reported fatalities with its therapeutic use. This report describes the case of a 40 year old brittle asthmatic patient who died after treatment with intravenous N-acetylcysteine. Asthma is a risk factor for adverse reactions to N-acetylcysteine and special caution should be exercised in its use in brittle asthmatic patients.

[The usefulness of troponin I in the diagnosis of cardiac damage in acute carbon monoxide poisoning]

Tissue hypoxia in carbon monoxide poisoning is often responsible for cardiac damage that is not always registered in ECG recordings. It is therefore necessary to look for biochemical markers of this damage. Troponin I, the protein not detected in serum of healthy people meets these criteria as its presence proves the cardiac damage. The aim of this paper was to evaluate the usefulness of troponin I determination in diagnosing cardiac damage in acute carbon monoxide poisoning. The study was performed in a group of 44 patients treated because of carbon monoxide poisoning. In addition, other biochemical markers of cardiac damage were determined. The results of the study showed that of the 44 cases of carbon monoxide poisoning, only in 16 patients troponin I was not found in serum. The level of troponin I was increased in all cases with ECG changes, but also in 13 patients with normal ECG.

Extracellular putrescine content after acute excitotoxic brain damage in the rat

We examined the effects of the local infusion of kainic acid (KA), by reverse dialysis in the rat striatum, on the concentration of polyamines in the extracellular striatal compartment and in tissue. KA infusion markedly increased (3-fold) extracellular putrescine (PUT) concentration, which reached its maximum at the end of the dialysis experiments (6 h). Tissue PUT concentration was also increased (2-fold) in the striatum perfused with KA but not in the contralateral side. Extracellular spermidine (SD) concentration but not tissue SD concentration was affected by KA. The increase in PUT was accompanied by histological damage around the probe and by an increase in ornithine decarboxylase content, as assessed by immunohistochemistry. These results indicate that in the first stages of the excitotoxic lesion, there is an increase in the extracellular concentrations of PUT and SD.

Expression of EMAP-II by activated monocytes/microglial cells in different regions of the rat hippocampus after trimethyltin-induced brain damage

Endothelial monocyte-activating polypeptide-II (EMAP-II), a novel cytokine with proinflammatory and antiangiogenic properties, has previously been shown to be expressed by activated monocytes/microglial cells in the rat brain and was therefore considered a useful marker to stage microglial activation in inflammatory lesions. The aim of the present immunohistochemical study was to investigate expression of EMAP-II in the rat hippocampus after intoxication with the organotin compound trimethyltin (TMT). Administration of this neurotoxicant is known to produce brain damage mainly affecting the hippocampal formation, with severe neuronal cell loss being observed predominantly in regions CA-1 and CA-3. The maximum severity of TMT-induced brain damage is observed 21 days after a single ip administration. In this well-characterized model of neurodegeneration, activated microglial cells have been described to occur mainly in the early stages of TMT-induced neurotoxicity. Following TMT intoxication, we observed a significant increase in EMAP-II(+) monocytes/microglial cells in the CA-1 and the CA-3 regions. The CA-2 region, however, was largely spared. While appearance of single EMAP-II(+) microglial cells was observed already after 5 days, EMAP-II immunoreactivity reached its maximum after 21 days and persisted in some of the rats up to 35 days. These findings show a close correlation to the temporal and spatial pattern of neuronal damage described in the rat hippocampus after TMT administration previously. Thus, upregulation of EMAP-II by activated monocytes/microglial cells may serve as a sensitive marker of neurotoxic lesions in the rat brain.

Serial diffusion-weighted MR Imaging in delayed postanoxic encephalopathy. A case study

We report a case of delayed postanoxic encephalopathy (DPE) studied with serial diffusion weighted imaging five times in a one-year period along with apparent diffusion coefficient (ADC) map as well as ADC values of periventricular white matter. Compared to the normal value, the ADC values of the white matter were initially low on the three (0.68 +/- 0.08 x 10(-3) mm(2)/s) and seven-week images (0.67 +/- 0.08 x 10(-3) mm(2)/s) but gradually recovered to the normal range on the four, six, and twelve-month images (0.78 +/- 0.05, 0.80 +/- 0.05 and 0.87 +/- 0.11 x 10(-3) mm(2)/s, respectively). Among the several pathogenetic mechanisms associated with DPE, these serial changes may be consistent with cytotoxic edema, from apoptosis, triggered by hypoxia.

Caramiphen and scopolamine prevent soman-induced brain damage and cognitive dysfunction

Exposure to soman, a toxic organophosphate nerve agent, causes severe adverse effects and long term changes in the peripheral and central nervous systems. The goal of this study was to evaluate the ability of prophylactic treatments to block the deleterious effects associated with soman poisoning. scopolamine, a classical anticholinergic agent, or caramiphen, an anticonvulsant anticholinergic drug with anti-glutamatergic properties, in conjunction with pyridostigmine, a reversible cholinesterase inhibitor, were administered prior to sbman (1 LD50). Both caramiphen and scopolamine dramatically attenuated the process of cell death as assessed by the binding of [3H]RoS-4864 to peripheral benzodiazepine receptors (omega3 sites) on microglia and astrocytes. In addition, caramiphen but not scopolamine, blocked the soman-evoked down-regulation of [3H]AMPA binding to forebrain membrane preparations. Moreover, cognitive tests utilizing the Morris water maze, examining learning and memory processes as well as reversal learning, demonstrated that caramiphen abolished the effects of soman intoxication on learning as early as the first trial day, while scopolamine exerted its effect commencing at the second day of training. Whereas the former drug completely prevented memory deficits, the latter exhibited partial protection. Both agents equally blocked the impairment of reversal learning. In addition, there is a significant correlation between behavioral parameters and [3H]RoS-4864 binding to forebrain membrane preparations of rats, which participated in these tests (r(21) = 0.66, P < 0.001; r(21) = 0.66, P < 0.001, -0.62, P < 0.002). These results demonstrate the beneficial use of drugs exhibiting both anti-cholinergic and anti-glutamatergic properties for the protection against changes in cognitive parameters caused by nerve agent poisoning. Moreover, agents such as caramiphen may eliminate the need for multiple drug therapy in organophosphate intoxications.

ATP-independent anoxic activation of ATP-sensitive K+ channels in dorsal vagal neurons of juvenile mice in situ

The role of ATP in anoxic activation of ATP-sensitive K+ (KATP) channels was studied in dorsal vagal neurons of mouse brainstem slices. In the whole-cell configuration, cyanide-induced chemical anoxia evoked within 10 s a 300-pA outward current that gave rise to a hyperpolarization of 24 mV. These responses were mimicked by nitrogen-aerated saline, rotenone or diazoxide and abolished by tolbutamide. The cyanide-induced hyperpolarization was due to activation of 70 pS K(ATP) channels that were half-maximally blocked by 5 microM internal ATP. Dialyzing the cells with either 1, 20 or 0 mM ATP did not, however, affect the time to onset, the kinetics or the magnitude of the cyanide-induced hyperpolarization. Impairment of ATP consumption by ouabain, vanadate or reduced temperature had no effect either. Thus, anoxia-induced activation of these KATP channels cannot be explained by a fall of cellular ATP or a concomitant rise of ADP. Anoxia-related changes of the actin cytoskeleton or the composition of the plasma membrane are also not likely to be involved, as cytochalasin D did not affect the cyanide-evoked hyperpolarization and phosphatidylinositol 4,5-bisphosphate failed to decrease the ATP sensitivity of single KATP channels. Finally, because of a lack of effects of reduced/oxidized glutathione and the oxidase blocker diphenyliodonium on the cyanide-induced hyperpolarization, cellular redox state does not appear to be involved. Our results indicate that despite a high sensitivity to ATP in excised patches, anoxic activation of KATP channels is independent of cellular ATP. Rather the ATP block seems to be removed as a consequence of impaired mitochondrial function.

[Time course of toxic hypoxic encephalopathy during combined therapy including hyperbaric oxygenation]

The mechanisms of action of hyperbaric oxygenation (HBO) in toxic hypoxic encephalopathy (THE) were studied using clinical psychopathological examinations, functional and laboratory tests in 268 patients with THE treated by a therapeutic complex including HBO and 75 patients with THE treated routinely (controls). The earliest possible addition of HBO to a complex of treatment of THE patients led to involution of signs of brain edema shown by computer tomography (CT) and improvement of its functional activity, while in patients exposed to HBO later the psychoorganic symptoms and CT signs of cerebral ischemia did not disappear. Detoxifying, neuroimmunomodulating, and neuroimmunostimulating effects of HBO in THE were demonstrated. Early HBO treatment decreased the dysfunction of various compartments of the brain characteristic of THE. The technology of HBO developed by the authors prevented the development of socially dysadapting psychoneurological disorders and reduced the mortality of THE patients.

Chemical hypoxia in hippocampal pyramidal cells affects membrane potential differentially depending on resting potential

The aim of the present study was to analyze the effect of chemical hypoxia (cyanide) on the membrane potential of hippocampal CA1 neurons and to elucidate the reason for previously found differences in the reaction to hypoxia in these cells. Recordings were performed in brain slices from 8-19-day-old rats with whole-cell patch clamp on cells identified with near-infrared video microscopy. Cyanide (0.1-2.0 mM) caused different responses depending on the resting potential of the cells: hyperpolarization (or an initial depolarization followed by hyperpolarization) was generally seen in cells with less negative resting potential (-56+/-6.1 mV), and depolarization in cells with more negative resting potential (-62+/-3.4 mV). After 10 min in cyanide the membrane potential in all cells had reached approximately the same level (-62+/-5.8 mV), the direction and size of the voltage response having an inverse linear relation to the resting potential (k=-0.98, r=0.71). The direction of the cyanide response was not reversed by current injection (depolarization by 12 mV) in cells with more negative resting potential (-60+/-2.8 mV). Wash out of cyanide caused hyperpolarization in 70% of the cells. Presence of ouabain (2 microM) resulted in pronounced depolarization during cyanide perfusion, and potentiated the hyperpolarization during wash out indicating that this part of the effect is not dependent on a reactivation of the Na/K pump. In conclusion, chemical hypoxia with cyanide changes the membrane potential in CA1 cells in size and direction depending on the original resting potential of the cells. The present findings suggested that cyanide activated not only K+ channels but in addition increased a Na+ current which has a more positive equilibrium potential.

Screening for cerebroprotective agents using an in vivo model of cerebral reversible depolarization in awake rats

The need to screen cerebroprotective compounds without anesthetic interference prompted the development of a model using hypoxic rats. In this model two outcome measures were used: (1) the time to reach isoelectric electroencephalogram (iEEG), caused by nitrogen gas inhalation in the test chamber, and (2) the time for behavioral recovery measuring the latency of restoration of the head-withdrawal reflex upon vibrissae stimulation. We report here data of blood chemistry, cerebral tissue oxygen measurements, a definition of a proposed scoring system, and the pharmacological results of RGH-2202. The findings with RGH-2202 are used here to show the utility of the screening method. Events during hypoxia: Arterial and venous pO(2), pCO(2), and pH, and brain tissue pO(2)significantly declined. Significant correlations were established among the pO(2)of cerebral tissue, blood, and the test chamber. RGH-2202 significantly and dose-dependently shortened the iEEG time; the compound's Effective Dose(30)was 227.8 mg kg(-1). Events during recovery: Immediately after the iEEG, when the atmosphere in the chamber was replaced with room air, the arterial, venous and brain tissue pO(2)increased above the control level and subsequently recovered to baseline levels. Behavioral recovery occurred before blood chemistry was otherwise normalized. RGH-2202 significantly and dose-dependently shortened the recovery time; the Effective Dose(30)was 8.71 mg kg(-1). The available data define and support the physiological basis of this practicable rat-screening model.

Effect of beta-hydroxybutyrate, a cerebral function improving agent, on cerebral hypoxia, anoxia and ischemia in mice and rats

Although improving energy metabolism in ischemic brain has been accepted for the treatment of cerebrovascular diseases, administration of glucose, as an energy substrate, would aggravate ischemic brain damage via activating anaerobic glycolysis, which leads to lactate accumulation. Beta-hydroxybutyrate (BHB) is one of the ketone bodies that can be utilized as an energy source during starvation. The purpose of our study was to define the protective effects of BHB on brain damage induced by hypoxia, anoxia and ischemia. The isotonic solution of BHB administered 30 min before the induction of ischemia at doses over 50 mg x kg(-1) x h(-1) showed remarkable protective effects against hypoxia and anoxia. BHB administered immediately after a bilateral carotid artery ligation at a dose of 30 mg x kg(-1) x h(-1) significantly suppressed the elevation of cerebral water and sodium contents as well as maintaining high ATP and low lactate levels. In contrast, glycerin, a hypertonic agent, substantially reduced the water content but did not show any significant effect on other parameters. We demonstrated that BHB, unlike glycerin, when used as an energy substrate in ischemic brain, has protective effects on cerebral hypoxia, anoxia and ischemia-induced metabolic change.

Lack of protective effect by intermittent hypoxia on MPTP-induced neurotoxicity in mice

In the study we report here, several lines of evidence support the preventive action of intermittent hypoxia against oxidative injuries in CNS. Our in vitro data showed that autooxidation and iron-induced lipid peroxidation were attenuated in cortical homogenates of intermittent hypoxia-treated animals. Furthermore, our preliminary study found that iron induced oxidative injuries were abolished in rat brain after intermittent hypoxic treatment (paper submitted). Several antioxidative defensive systems improve in response to intermittent hypoxia. Since attenuation of autooxidation and iron-induced lipid peroxidation were observed in cortical homogenates of intermittent hypoxia-treated mice, the lack of prevention by intermittent hypoxia of MPTP-induced neurotoxicity may be due to the MPTP action that is not oxidative related. Together with our previous studies, in which several antioxidants were shown to successfully prevent oxidative injuries, our data here suggest that intermittent hypoxia may offer a potential treatment for preventing CNS degenerative diseases.

Delta activity as an early indicator for soman-induced brain damage: a review

The organophosphorus (OP) compound soman is known to produce long-lasting epileptic seizure activity and associated brain damage. The present paper reviews the findings of five recent studies that tentatively established correlations between the development of soman-induced neuropathology and some subtle changes in the electrocortigraphic (ECoG) power spectrum. It is important to note that the reported experiments have been performed independently by three different teams (France, The Netherlands, USA) in various animal models (rat, guinea-pig, cynomolgus monkey) through different protocols of intoxication, pharmacological environments, and methods for ECoG spectral analysis. Despite these disparities, the five studies show that a suistained shift of ECoG power toward the lowest frequency range, i.e. the delta band, occurs within the first hours of soman-induced seizures. This early ECoG spectral change is concurrent with the first neuropathological changes in brain and is almost constantly followed, days or weeks later, by at least minimal neuropathology. Moreover the relative contribution of delta activity to the ECoG power spectrum still remains abnormally high for 1-3 days after seizure onset, i.e. within the phase of damage maturation. On the other hand, somnan-induced neuropathology was not observed in non-seizuring animals in which the delta activity was not increased above the pre-soman baseline. Similarly, no brain damage was ever shown in seizuring subjects in which the initial delta change eventually normalized after the curative administration of efficient anticonvulsant drugs such as the non-competitive antagonists of the NMDA receptor. These results, in agreement with previously published observations, strongly suggest that an increase of the relative power in the delta band might be a real-time marker of the ongoing development of soman-induced, seizure-related cerebral lesions and a reliable predictor for the final neuronal losses to come. Therefore, the monitoring of delta activity during the 24-72 h period that follows soman exposure may potentially be a useful tool to follow "on-line" the progression of brain damage and to control the neuroprotective activity of'a medication. Moreover since the method is non-invasive in man and since the above-presented results have been partly found in primates, the applicability of spectral analysis as a prognostic means in human OP poisoning ought to be seriously considered.

Permanent brain damage following acute clonidine poisoning in Munchausen by proxy

A child presented with recurrent episodes of lethargia for which he underwent several hospital admissions and investigations. A further episode culminated in respiratory arrest and hypoxic ischemic encephalopathy with permanent mental regression. Eighteen months later the mother was discovered while providing clonidine pills to the child; the mother appears to feature a Munchausen syndrome by proxy.

[Lipogenesis in the brain under hypoxia]

This study investigated the utilization of some radioactive precursors [2(12)C]-acetate, [1-6(14)]-glucose, [5(14)C]-glutamate) for fatty acids and lipid biosynthesis in the rat brain under normal and hypoxic conditions. In severe hemic hypoxia (30-45 min after the injection of 15 mg of NaNO2/100 g body weight) there was a significant increase in 14C incorporation from glutamate into brain lipids (by 2.8 times) and into fatty acids (by 2.2 times) as compared to the control level. Enhanced lipogenesis from glutamate was demonstrated due to the activation of all alpha-ketoglutarate shunt steps. The higher lipogenesis from glutamate in the brain as a possible mechanism for this excitatory amino acid utilization under hypoxia.