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PubMed1989

Enhancement of murine phenytoin teratogenicity by the gamma-glutamylcysteine synthetase inhibitor L-buthionine-(S,R)-sulfoximine and by the glutathione depletor diethyl maleate.

The teratogenicity of phenytoin may result from its enzymatic bioactivation to a reactive intermediate, which, if not detoxified, can interact with embryonic tissues and alter development. Glutathione (GSH) is an important cofactor/substrate for many physiological processes and for the detoxification of xenobiotic reactive intermediates. This study examined the effects of the GSH depletor diethyl maleate (DEM) and the GSH synthesis inhibitor L-buthionine-(S,R)-sulfoximine (BSO) on phenytoin embryopathy. Phenytoin, 55 mg/kg, was administered intraperitoneally (ip) to pregnant CD-1 mice at 0900 hr on gestational days 12 and 13. Pretreatment with DEM, 150 or 300 mg/kg ip, enhanced the incidence of phenytoin-induced cleft palates by 3.3-fold and 2.3-fold, respectively (P less than 0.05), without affecting the incidence of resorptions, postpartum death, or mean fetal weight. BSO, 1,800 mg/kg ip, given 0.5 hr prior to phenytoin, resulted in a 2.4-fold increase in postpartum lethality and a 5-fold increase in fetal weight loss (P less than 0.05), without altering the incidence of resorptions or cleft palates. In two subsequent studies, BSO, 680-1,018 mg/kg/day, was given in the drinking water on gestational days 9 to 13 in the first study and on days 10 to 14 in the second study. Phenytoin, 55 mg/kg ip, was given on days 11 and 12 and on days 11 to 13 in the respective studies. In the first drinking water study, BSO enhanced the incidence of phenytoin-induced fetal resorptions 3.8-fold and cleft palates 3.3-fold (P less than 0.05) but did not affect postpartum death. In the second study, BSO enhanced the incidence of resorptions, cleft palates, and postpartum death by 2-fold, 2.6-fold, and 1.7-fold, respectively (P less than 0.05). In both of the latter two studies, phenytoin-induced fetal weight loss was altered by BSO treatment (P less than 0.05). BSO alone had no embryopathic effects. These results suggest that GSH may be involved in the detoxification of a reactive intermediate of phenytoin and/or in fetal cytoprotection.

Administration, Oral↗
PubMed1993

Neuronal vacuolization and necrosis induced by the noncompetitive N-methyl-D-aspartate (NMDA) antagonist MK(+)801 (dizocilpine maleate): a light and electron microscopic evaluation of the rat retrosplenial cortex.

MK(+)801 (dizocilpine maleate) is a noncompetitive antagonist at the N-methyl-D-aspartate (NMDA) receptor, the major glutamate receptor at excitatory synapses in the central nervous system. Since NMDA antagonists are neuroprotective, there is interest in their development for treatment of cerebral ischemia. Unfortunately, many of these compounds also induce vacuole formation in neurons of the rat retrosplenial cortex (Olney et al., Science 244: 1360-1362, 1989). Although vacuolization was initially reported to be reversible with MK(+)801, preliminary data later suggested that higher doses might produce neuronal necrosis. To explore this issue, young male Sprague-Dawley rats were given a single subcutaneous dose of vehicle or 1, 5, or 10 mg/kg MK(+)801. At 4 h and 1, 2, 3, 4, 7, and 14 days postdose (DPD), the retrosplenial cortex was examined by light and electron microscopy. At 4 h, vacuoles occurred in neurons of retrosplenial cortical layers 3 and 4 in all rats given MK(+)801. Mitochondria and endoplasmic reticulum contributed to vacuole formation. At 1 DPD, vacuoles or necrotic neurons were rarely observed. At all subsequent time points, necrotic neurons were readily evident in rats given 5 or 10 mg/kg MK(+)801, but only rarely evident in rats given 1 mg/kg. Necrotic neurons were associated with reactive microglial cells that contained electron-dense debris ultrastructurally. If similar dose-dependent neuronal necrosis proves to be a feature of other NMDA antagonists, such effects might raise concerns for the development and use of these compounds in human cerebrovascular diseases.

Animals↗
PubMed1994

Intrathecal administration of dizocilpine maleate (MK-801) attenuates ischemic damage in the rabbit spinal cord.

The therapeutic efficacy of intrathecally administered MK-801 (dizocilpine maleate), a noncompetitive receptor antagonist of N-methyl-D-aspartate receptor complex, was investigated in a rabbit spinal cord ischemia model. Normal saline, 0.3 ml (control, n = 4) or MK-801, 150 micrograms in 0.3 ml of saline, was administered intrathecally at the level of the lumbar enlargement, 30 min before (pretreatment, n = 7) or in the first min after (post-treatment, n = 4) 30 min of aortic occlusion followed by 2-h reperfusion. Nauta silver method was used for histopathological evaluation of lumbosacral segments. The degree of gray matter damage (argyrophilic neurons) was evaluated in three areas: A1, Rexed's laminae I-VI; A2, laminae VII and X; and A3, laminae VIII-IX. Pre- and post-treatment with MK-801 decreased the number of argyrophilic neurons (P < 0.05) in all areas examined. The number of argyrophilic neurons in A1, A2, and A3 was reduced by 59, 28, and 29%, respectively, by MK-801 pretreatment and by 87, 66, and 46%, respectively, by MK-801 post-treatment. Our results show that with single bolus intrathecal administration the efficacy of MK-801 was greater with post- compared to pretreatment and most dramatic in Rexed's laminae I-VI compared to laminae VII-X. Intrathecal administration of MK-801 prior to or at the beginning of the recirculation diminishes the extent of postischemic neuronal spinal cord damage at early postreperfusion period.

Animals↗
PubMed1993

Nephrotoxicity of pravadoline maleate (WIN 48098-6) in dogs: evidence of maleic acid-induced acute tubular necrosis.

Single oral administration of pravadoline maleate (WIN 48098-6), the maleic acid salt of WIN 48098, induced acute tubular necrosis (ATN) in male and female beagle dogs at dosages > or = 40 mg/kg (WIN 48098 base (31 mg/kg) and maleic acid (9 mg/kg)). Subsequent oral studies were conducted with equimolar dosages of maleic acid and WIN 48098-7, the ethanesulfonate salt of WIN 48098, to determine the nephrotoxic moiety of WIN 48098-6. ATN was observed for dogs given only maleic acid at single oral dosages > or = 9 mg/kg. This result provided evidence that maleic acid was responsible for the nephrotoxicity observed in dogs given single oral dosages of WIN 48098-6. The induction of maleic acid-related nephrotoxicity in dogs may confound the interpretation of toxicologic studies of maleic acid salts of basic pharmaceutics, if the dosage of test article results in the delivery of dosages of maleic acid > or = 9 mg/kg. Furthermore, the results of these studies underscore the importance of establishing maximum no-observed-effect dosages and target organ toxicity profiles for acids and bases that are commonly used in the development of salts of pharmaceutics.

Animals↗
PubMed1986

Effects of diethyl maleate on non-protein sulfhydryl content and cellular functions of mouse thymocytes in vitro.

The electrophilic compound diethyl maleate (DEM, 10(-5)-10(-3) M) decreased the content of non-protein sulfhydryl groups in mouse thymocytes in vitro and affected mitotic activity, spontaneous migration and viability of the cells. The mitotic activity of mouse thymocytes was most sensitive to DEM. It is probable that the decrease of the cell content of reduced glutathione (GSH) led to a failure of GSH-dependent cellular functions, such as mitosis and migration. Cytosolic supernatants of mouse and rat thymocytes exhibited GSH S-transferase activities on DEM and 1-chloro-2,4-dinitrobenzene as electrophilic substrates.

Animals↗
PubMed1994

Neuronal vacuole formation in the rat posterior cingulate/retrosplenial cortex after treatment with the N-methyl-D-aspartate (NMDA) antagonist MK-801 (dizocilpine maleate).

Cytoplasmic vacuoles appear in neurons of the posterior cingulate/retrosplenial cortex (PC/RS) of rats after treatment with N-methyl-D-aspartate (NMDA) receptor antagonists. Prominent dilatation of mitochondria and endoplasmic reticulum has been described within 2 h; however, the ultrastructural features of vacuole formation are unknown. To investigate this, the present study examined the PC/RS cortex of male rats (age 60-70 days) at 15, 30, 45, 60, 90, and 120 min after subcutaneous treatment with 1 mg/kg of the noncompetitive NMDA antagonist MK-801 (dizocilpine maleate, 5-methyl-10, 11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine). Subtle mitochondrial dilatation was identified in a few neurons as early as 15 min postdose (MPD). By 30 MPD, dilatation was more pronounced in mitochondria and also involved the endoplasmic reticulum and perinuclear space. Ribosomal disaggregation and degranulation were also evident by 30 MPD. At all subsequent time points, dilatation of mitochondria and endoplasmic reticulum progressed in severity. Although the relative involvement of mitochondria and endoplasmic reticulum varied, glia were not involved. These ultrastructural data suggest that after treatment with MK-801, mitochondrial dilatation precedes involvement of endoplasmic reticulum in vacuolization of susceptible PC/RS cortical neurons. The early mitochondrial effects identified in this study suggest an initial metabolic insult that rapidly progresses to affect endoplasmic reticulum and ribosomes. This strengthens the relationship between the ability of certain NMDA antagonists to induce energy perturbations and neuronal vacuoles in the same region of the rat cerebral cortex.

Animals↗
PubMed1983

Effect of adrenalectomy, pretreatment with SKF 525-A, phenobarbital and diethyl maleate on the acute toxicity of fenitrothion in male rats.

The effect of adrenalectomy (Adx), SKF 525-A, phenobarbital (PB), and diethyl maleate (DEM) on the acute toxicity of fenitrothion was investigated in male rats by assessing the degree of plasma cholinesterase activity. PB, 60 mg/kg/day for 3 days, exerted no protective effect on the toxicity of fenitrothion (100 mg/kg, p.o.) given 24 h after the last injection. In adrenalectomized and SKF 525-A-pretreated rats, the toxicity of fenitrothion was lower than that of the controls. Fenitrothion toxicity was increased by administration of DEM (1 ml/kg), which depletes hepatic glutathione (GSH) levels. In vitro, the rates of fenitrothion decomposition and fenitrooxon formation by microsomes were markedly affected by PB, SKF 525-A and Adx. The decomposition of fenitrooxon by the microsomal fraction and GSH-dependent decomposition of fenitrooxon by the soluble fraction were not affected by PB, SKF 525-A and Adx pretreatment. The GSH-dependent decomposition of fenitrothion and fenitrooxon was increased by addition of GSH to the incubation mixture. The present results indicate that the GSH-dependent metabolic pathway plays an important role in the detoxication of fenitrothion.

Adrenalectomy↗
PubMed1990

Effects of diethyl maleate (DEM), a glutathione depletor, on prostaglandin synthesis in the isolated perfused spleen of rabbits.

To investigate the role of glutathione (GSH) on prostaglandin (PG) synthesis, isolated rabbit spleens were perfused with Tyrode's solution with or without the addition of diethyl maleate (DEM) in concentrations up to 1 mM. In the absence of DEM, PG synthesis was stimulated by the Ca2+ ionophore A23187 (20 nmole) or arachidonate (0.4 mumole). Prostaglandin (PG) E2 was a major product, accounting for 60-70% of the total cyclooxygenase products. Small amounts of PGF2 alpha, 6-keto-PGF1 alpha, PGD2 and thromboxane (Tx) B2 were also produced. When DEM was added to the perfusion medium, GSH content decreased dose-dependently with increasing DEM concentration. Lactate dehydrogenase activity was not detected in the venous effluent, indicating that DEM depleted intrasplenic GSH without causing any lysis of cellular membranes. A23187-induced production of PGs and of Tx was decreased with increasing concentrations of DEM up to 0.5 mM, whereas at 1.0 mM DEM, these products showed a tendency to increase as compared with levels at 0.5 mM DEM. However, this increase was only significant for TxB2, which returned to levels obtained in the absence of DEM. DEM 1 mM did not cause cell lysis, but it appears to perturb the cell membrane to a degree similar to that which occurs with stimulation of phospholipase A2. The small but significant increase of TxB2 with 1.0 mM DEM could be a result of decreased PGE2 isomerase activity. Perfusion with arachidonate gave virtually identical results: 1.0 mM DEM attenuated the production of all prostanoids except for TxB2 as compared with untreated controls. These results suggest that GSH contributes to the regulation and/or maintenance of PGs synthesis.

Animals↗
PubMed1987

Histamine as a ligand in blood plasma. Part 7. Malate, malonate, maleate and tartrate as adjuvants of zinc to favour histamine tissue diffusion through mixed-ligand coordination. In vitro tests on lymphocyte proliferation.

Investigations based on computer simulated distributions of histamine in blood plasma were recently devoted to the assessment of the roles of cysteine, aspartic and glutamic acids as possible adjuvants of zinc to favour histamine tissue diffusion through mixed-ligand coordination. Since all tissues contain at least one of the two enzymes required for the catabolism of histamine, any increase of its tissue diffusion is expected to result in an acceleration of its degradation, which may be of interest for the treatment of anaphylactic disorders. As an extension of these studies, the present paper first reports (i) an experimental investigation of the tendency of four dicarboxylic acids, namely malate, malonate, tartrate and maleate, to mixed-ligand coordination with zinc and histamine, (ii) computer-based potential effects to be expected from the association of these agents to zinc with respect to histamine tissue diffusion. Cell culture studies were then used to test simulation expectations. Two series of experiments involving successively human lymphocytes and a lymphoblastoid cell line (8866) have been carried out, which led to the following conclusions: (i) the hypothesis formerly put forward that cysteine could favour histamine tissue diffusion through mixed-ligand coordination with zinc has been validated on the two cell models, (ii) the formerly established suppressive role of histamine versus lymphocyte proliferation has clearly been confirmed, (iii) moreover, this suppressive effect has been shown to occur correlatively to histamine uptake by these cells, (iv) the four dicarboxylic acids, more especially tartric acid, proved effective as catalysts of the two above processes. Possible biomedical applications of these results are discussed.

Cell Line↗
PubMed1995

Velnacrine maleate improves delayed matching performance by aged monkeys.

Velnacrine maleate is a novel, orally active acetylcholinesterase inhibitor of the acridine class with a longer duration of action than physostigmine. Velnacrine has shown efficacy in the treatment of Alzheimer's disease and in improving both normal and experimentally impaired mnemonic function in animals and humans. To characterize this action further, the present study evaluated velnacrine for its ability to ameliorate the decline in short-term memory associated with aging in non-human primates at two time points after velnacrine administration: (1) 30 min and (2) 24 h. Initially, doses of 1, 2, 4, and 6 mg/kg, PO (free base corrected) were administered once to each of six aged (25-40 years), memory-impaired macaques that had been trained to perform a delayed matching-to-sample (DMTS) paradigm. The dose associated with the greatest improvement in session performance was administered three more times to the same individual. Four of the six monkeys showed improved DMTS performance during the repeated best dose phase (phase 2). Almost all of the improvement occurred during long-delay trials. Compared to placebo trials, velnacrine induced a significant improvement of long delay DMTS (58.0-66.7%, 13.4% of the placebo value). Long delay DMTS remained significantly improved during the test session conducted 24 h following velnacrine administration. Pharmacokinetic analysis following administration of 4 or 6 mg/kg velnacrine to three aged monkeys revealed peak plasma concentrations ranging from 27 to 166 ng/ml, 30-60 min after dosing. Six hours after dosing velnacrine plasma levels decreased to 5.1-11.8 ng/ml; and 24 h after dosing velnacrine plasma levels were less than the limit of quantitation (5 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

Diethyl maleate, an in vivo chemical depletor of glutathione, affects the response of male and female rats to arsenic deprivation.

An experiment was performed to determine the effect of diethyl maleate (DEM), an in vivo depletor of glutathione, on the response of male and female rats to arsenic deprivation. A 2 x 2 x 2 factorially arranged experiment used groups of six weanling Sprague-Dawley rats. Dietary variables were arsenic at 0 or 0.5 microgram/g and DEM at 0 or 0.25%; the third variable was gender. Animals were fed for 10 wk a casein-ground corn based diet that contained amounts of calcium, phosphorus, and magnesium similar to the AIN-76 diet. DEM supplementation increased blood arsenic in both male and female rats; female rats had the greatest amount of arsenic in whole blood. Although female rats in general had a lower concentration of glutathione in liver, those fed no supplemental DEM, regardless of their arsenic status, had the lowest amounts. Compared to males, female rats had a lower activity of liver glutathione S-transferase (GST). Arsenic deprivation decreased, and DEM supplementation increased liver GST activity in both male and female rats. Lung GST activity was also increased by DEM supplementation in male, but not female, rats. The most striking finding of the study was that compared to males, females had extremely elevated kidney calcium concentrations, and that the elevation was exacerbated by arsenic deprivation. DEM supplementation also exacerbated the accumulation of calcium in the kidney of the female rats. The response of the rat to both DEM and arsenic was, for many variables, dependent on gender. This gender dependence may be explained by the differences in methionine metabolism between male and female rats. Thus, arsenic deprivation apparently can manifest itself differently depending on gender.

Analysis of Variance↗
PubMed1978

Effect of malonate and maleate on growth and brefeldin A formation in Curvularia lunata.

Malonate exerted a stronger inhibitory effect on brefeldin A production than on mycelia growth in cultures of Curvularia lunata especially at inhibitory levels of 100 to 200 mM. The extent of 200 mM malonate inhibition of growth and brefeldin A production was greater in cultures treated with malonate prior to inoculation than those treated following 5 days after inoculation. Maleate at levels of 40 to 220 mM activated brefeldin A formation in cultures though exerting variable effects on mycelia growth.

Anti-Bacterial Agents↗
PubMed2006

Effect of diethyl maleate induced oxidative stress on male reproductive activity in mice: redox active enzymes and transcription factors expression.

Free radicals and reactive oxygen species (ROS) associated with oxidative stress are likely to play a number of significant roles in male reproduction. Present study was carried out to evaluate the effect of diethyl maleate (DEM) induced oxidative stress on male fertility in mice. Intraperitoneal injection of DEM for two weeks resulted in decrease in reduced glutathione and increase in the oxidized glutathione levels in the testis. Effect on the reproductive ability in term of sperm concentration, motility and fertility status was studied. Sperm concentration and motility were found to be significantly reduced along with a significant reduction in the litter size. Expression of redox sensitive transcription factor, cjun and cfos genes, along with gamma-glutamyl cysteine synthetase (GCS) and manganese superoxide dismutase (MnSOD) expression were also studied using RT-PCR after DEM treatment. RT-PCR analysis revealed decrease in the testicular mRNA expression for cjun and cfos whereas the expression for GCS and MnSOD increased. Enzyme activity of SOD also increased. The study reflects the effect of DEM induced oxidative stress on the reproductive ability of male mice and interplay of the various components of the antioxidant defense system and redox regulated transcription factors at the transcriptional level.

Animals↗
PubMed1982

Effect of diethyl maleate on the biliary excretion rate of infused sulfobromophthalein-glutathione.

Diethyl maleate (DEM) was given intraperitoneally to rats in a dose (4.3 mmoles/kg) known to markedly decrease glutathione levels in liver. DEM induced a choleresis previously shown to be due to the osmotic activity of DEM conjugates (DEM-glutathione and subsequent metabolic products) excreted into bile. Coincident with the choleresis, the biliary excretory Tm for the infused glutathione conjugate of sulfobromophthalein (BSP-GSH) was depressed significantly. The data are interpreted as indicating that DEM-GSH conjugates compete with BSP-GSH conjugates for a canalicular carrier mechanism.

Animals↗
PubMed1992

Effects of buthionine sulfoximine and diethyl maleate on glutathione turnover in the channel catfish.

Despite the growing use of fish in toxicological studies, little is known regarding glutathione (GSH) metabolism and turnover in these aquatic species. Therefore, we examined GSH metabolism in the liver and gills of channel catfish (Ictalurus punctatus), a commonly employed aquatic toxicological model. Treatment of channel catfish with L-buthionine-S,R-sulfoximine (BSO, 400 or 1000 mg/kg, i.p.), an inhibitor of GSH biosynthesis, did not deplete hepatic GSH in channel catfish. In addition, hepatic GSH concentrations did not fluctuate in catfish starved for 3 days, indicating relatively slow turnover of hepatic GSH. However, hepatic GSH concentrations were reduced significantly (P less than 0.05) after 7 days of starvation. Administration of the thiol alkylating agent diethyl maleate (DEM, 0.6 mL/kg, i.p.) resulted in depletion of 85% of hepatic GSH at 6 hr post-DEM, with complete GSH recovery observed at 24 hr post-DEM. Co-administration of BSO and DEM (1000 mg/kg, 0.6 mL/kg, respectively) substantially depleted gill GSH and eliminated detectable liver GSH. Following BSO/DEM, GSH recovery in hepatic mitochondria occurred more rapidly than did liver cytosolic GSH. gamma-Glutamylcysteine synthetase (GCS) activities were comparable in the 10,000 g supernatants of catfish liver and gills (204 +/- 21 and 268 +/- 20 nmol/min/mg protein, respectively) whereas gamma-glutamyltranspeptidase (GGT) activity was not detected in the 600 g post-nuclear fraction of either liver or gills. In conclusion, i.p. administration of DEM was an effective means for achieving short-term hepatic GSH depletion in channel catfish, whereas co-administration of BSO and DEM elicited prolonged and extensive hepatic GSH depletion in this species. Like rodents, channel catfish maintained physiologically distinct hepatic mitochondrial and cytosolic GSH pools, and also regulated hepatic GSH levels by in situ hepatic GSH biosynthesis. However, unlike rodents, there was no evidence for a labile hepatic cytosolic GSH pool in channel catfish. These similarities and differences need to be considered when designing toxicological studies involving the GSH pathway in channel catfish and possibly other fish species.

Animals↗
PubMed1989

The effect of the excitatory amino acid receptor antagonist dizocilipine maleate (MK-801) on hemispheric cerebral blood flow and metabolism in dogs: modification by prior complete cerebral ischemia.

The effect of the N-methyl-D-aspartate (NMDA) receptor antagonist dizociplipine maleate (MK-801) on cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), intracranial pressure and systemic variables was examined in 6 normal dogs (Group I). In 6 additional dogs (Group II), the effects of a prior 11 min episode of complete cerebral ischemia on the response to dizocilipine was studied. CBF was measured with a sagittal sinus outflow technique and CMRO2 was calculated as the product of CBF and the arterial to sagittal sinus O2 content difference. Dizocilipine was administered as a 150 micrograms/kg i.v. bolus followed by a 75 micrograms.kg-1.h-1 infusion for 90 min. Plasma dizocilipine levels were greater than 25 ng/ml for the duration of the infusion. The CSF levels were approximately half the plasma levels. Five minutes after initiation of dizocilipine treatment, Group I dogs experienced a 63% increase in heart rate (P less than 0.01) and an 8% decrease in the mean arterial blood pressure (P less than 0.05). Over the same time interval. CBF increased by 85% (P less than 0.01) and intracranial pressure nearly doubled (P less than 0.05). In addition, dizocilipine treatment in all Group I animals resulted in EEG quasiperiodic bursts of delta-waves and polyspikes on a background of beta-activity. With the exception of the intracranial pressure, the above changes in systemic and cerebral variables persisted for the duration of the drug infusion. Intracranial pressure was no longer significantly elevated after 80 min of drug infusion. Hemispheric CMRO2 was unchanged by dizocilipine in Group I dogs. There was a decrease in the cortical glucose level at the end of the study, but no significant change in phosphocreatine, ATP, lactate, or energy charge when compared with 6 laboratory normals. An identical dose of dizocilipine administered after an 11 min episode of complete cerebral ischemia resulted in no significant changes in either cerebral or systemic variables. The absence of systemic effects in Group II dogs suggests that dizocilipine administration in normal dogs results in a centrally mediated activation of the peripheral sympathetic nervous system. The uncoupling of CBF and CMRO2 observed following dizocilipine treatment is similar to that reported for two other known NMDA antagonists, ketamine and phencyclidine. If administration of dizocilipine results in improved histopathological and neurological outcome following an episode of complete cerebral ischemia, this improvement is unrelated to changes in postischemic CBF or hemispheric CMRO2.

Animals↗
PubMed1989

Evaluation of the glutamate antagonist dizocilipine maleate (MK-801) on neurologic outcome in a canine model of complete cerebral ischemia: correlation with hippocampal histopathology.

This study was designed to determine if dizocilipine maleate (MK-801), administered following 11 min of complete ischemia in dogs, could favorably alter neurologic outcome and hippocampal damage. Eighteen dogs were anesthetized and subjected to complete cerebral ischemia by temporary occlusion of the ascending aorta and the venae cavae via a thoracotomy. Five min postischemia, 9 dogs were given dizocilipine 150 micrograms/kg, followed by an infusion of 1.25 microgram/kg/min for 8 h. Control dogs were given equal volumes of placebo. Dogs were evaluated neurologically at 24, 48, and 72 h; thereafter, the brains were perfused, fixed and harvested. There was no significant difference in outcome between dizocilipine- and placebo-treated dogs: 5 of 9 given dizocilipine were normal, 1 was mildly injured and 3 were severely injured or dead. In the control animals given placebo, 3 of 9 were normal, 2 were mildly injured and 4 were moderately to severely injured. Histopathologic examination was limited to the hippocampus. CA1 and CA2,3,4 pyramidal neurons were graded according to degree of injury on a 5-point scale. There were no differences in histopathologic grades between the two groups. However, in both groups combined there was a significant correlation between neurologic outcome grade and histopathologic grade. The only notable systemic effect of dizocilipine appeared to be prolonged sedation which extended beyond 24 h postischemia but was not evident at 48 h postischemia. The authors conclude that more outcome studies in more sensitive models are needed.

Animals↗
PubMed1995

Hyperthermia nullifies the ameliorating effect of dizocilpine maleate (MK-801) in focal cerebral ischemia.

The present study was inspired by two previous findings from the laboratory. The first was that dizocilpine maleate (MK-801) fails to reduce infarct size when the middle cerebral artery (MCA) is permanently occluded by an intraluminal filament technique in rats. In seeking the reasons for this we measured temperature and found that the body temperature of occluded animals increases to 39.0-39.5 degrees C during the first 2-3 h. In order to explore whether the rise in temperature was responsible for the lack of effect of MK-801, two groups of animals were studied, both containing animals which were subjected to 2 h of transient MCA occlusion and given MK-801 15 min before, as well as 6 and 24 h after ischemia. In one group, temperature was allowed to rise spontaneously during ischemia (39.0-39.5 degrees C). In the other, body temperature was maintained close to normal during ischemia, and for the first 6 h postischemically, by cooling of the ambient air. Infarct volume was assessed by triphenyltetrazolium chloride staining after 48 h of recovery. The results showed that MK-801 failed to reduce infarct size in animals whose body temperature rose during ischemia. In contrast, the drug markedly reduced infarct volume in temperature-controlled animals; in fact, 5/8 animals had no infarcts but selective neuronal damage only. The results suggest that amelioration of focal ischemic damage cannot be expected if body and brain temperature is allowed to rise above normal.

Animals↗