Anticonvulsive profile of two GABAB receptor antagonists on acute seizure mice models.

INTRODUCTION: DL-3-hydroxy-3-phenylpentanamide (HEPP) and DL-3-hydroxy-3-(4'chlorophenyl)-pentanamide (Cl-HEPP) are phenyl-alcohol-amides that are metabotropic GABAB receptor (MGBR) antagonists and protective against absence seizures. This study aims to further characterize the anticonvulsant profile of these drugs. METHODS: HEPP and Cl-HEPP were evaluated in various standardized acute seizure and toxic tests in female Swiss-OF1 mice. RESULTS: Toxicities of HEPP and Cl-HEPP were limited; doses up to 30 mg/kg did not result in hypothermia, reduced spontaneous locomotor activity, or failure of the rotarod test, with doses >15 mg/kg potentiating pentobarbital-induced sleep. In maximal electroshock-induced seizures, 20 mg/kg Cl-HEPP protected 100 % of mice; lower doses shortened post-ictal recovery. Seizure protection occurred against subcutaneous pentylenetetrazole and picrotoxin, being limited against N-methyl-d-aspartate. In bicuculline test, clonic or fatal tonic seizures were decreased, onset delayed, and recovery improved; ED50 values (dose protecting 50 % of the animals) were 37.5 and 25 mg/kg for HEPP and Cl-HEPP, respectively. In magnesium deficiency-dependent audiogenic seizures (MDDAS), ED50 values were 3 and 8 mg/kg for Cl-HEPP and HEPP, respectively. The components of MDDAS (latency, wild running, seizure, and recovery phases) in unprotected animals were only minimally affected by near ED50 doses of Cl-HEPP and HEPP. DISCUSSION: HEPP and, to a greater extent, Cl-HEPP provide anti-seizure protections in several acute seizure tests in mice at nontoxic doses. These results are consistent with the action of these drugs on diverse molecular targets directly resulting from their MGBR antagonistic properties. However, other mechanisms might occur possibly for the protection given in the MES test. Finally, a similarity in the modulation of MDDAS components between the two phenyl alcohol amides and ethosuximide could also be based on the MGBR antagonistic properties of the former, given the recently re-evaluated therapeutic relevant targets of the latter.

The protective effect of dietary Arthrospira (Spirulina) maxima against mutagenicity induced by benzo[alpha]pyrene in mice.

Benzo[alpha]pyrene (B[α]P) was used to test the possible antimutagenic effects of Arthrospira (Spirulina) maxima (SP) on male and female mice. SP was orally administered at 0, 200, 400, or 800 mg/kg of body weight to animals of both sexes for 2 weeks before starting the B[α]P (intraperitoneal injection) at 125 mg/kg of body weight for 5 consecutive days. For the male dominant lethal test, each male was caged with two untreated females per week for 3 weeks. For the female dominant lethal test, each female was caged for 1 week with one untreated male. All the females were evaluated 13-15 days after mating for incidence of pregnancy, total corpora lutea, total implants and pre- and postimplant losses. SP protected from B[α]P-induced pre- and postimplant losses in the male dominant lethal test, and from B[α]P-induced postimplantation losses in treated females. Moreover, SP treatment significantly reduced the detrimental effect of B[α]P on the quality of mouse semen. Our results illustrate the protective effects of SP in relation to B[α]P-induced genetic damage to germ cells. We conclude that SP, owing mainly to the presence of phycocyanin, could be of potential clinical interest in cancer treatment or prevention of relapse.

Brain anticonvulsant protection of mice given chronic carbamazepine under various fatty acid and magnesium diet conditions.

The anticonvulsant and mood stabilizer drug carbamazepine (CBZ) was evaluated for anti-seizure activity after drug pretreatment of young weaning mice given various oil-based diets. These diets had various mono-(MUFA) and poly-(PUFA) unsaturated fatty acid contents, were associated or not with magnesium deprivation, and were given over the entire experimental period (34 days). The diets included a commercial and three purified synthetic diets (n-6 PUFA, n-3 PUFA and MUFA-based chows containing 5% corn/sunflower oils 1:3, 5% rapeseed oil and 5% high oleic acid sunflower oil/sunflower oil 7:3, respectively). A 10-days CBZ treatment (50 mg/kg/day fragmented in two daily intraperitoneal injections of 25 mg/kg) was given 20 days after initiating diet administration and evaluations of mice was performed 4 days after arrest of CBZ in various seizure tests. In these conditions, CBZ pretreatment still exhibited anticonvulsant protection especially in magnesium-deficient animals. Ethosuximide (ESM)-like profiles under MUFA and n-3 PUFA diets and unusual GABA(A)ergic profile under n-6 PUFA diet in magnesium-deficiency dependent audiogenic seizures (MDDAS) test as well as protection against NMDA-induced seizures in all lipid (n-3 PUFA>MUFA and n-6 PUFA) diet conditions were observed in CBZ-pretreated mice. By highlighting ESM-like and anti-NMDA mechanisms previously induced by an n-3 PUFA diet, present CBZ anticonvulsant properties suggest brain protective targets common to CBZ and n-3 PUFAs.

Dairy fat blends high in α-linolenic acid are superior to n-3 fatty-acid-enriched palm oil blends for increasing DHA levels in the brains of young rats.

Achieving an appropriate docosahexaenoic acid (DHA) status in the neonatal brain is an important goal of neonatal nutrition. We evaluated how different dietary fat matrices improved DHA content in the brains of both male and female rats. Forty rats of each gender were born from dams fed over gestation and lactation with a low α-linolenic acid (ALA) diet (0.4% of fatty acids) and subjected for 6 weeks after weaning to a palm oil blend-based diet (10% by weight) that provided either 1.5% ALA or 1.5% ALA and 0.12% DHA with 0.4% arachidonic acid or to an anhydrous dairy fat blend that provided 1.5% or 2.3% ALA. Fatty acids in the plasma, red blood cells (RBCs) and whole brain were determined by gas chromatography. The 1.5% ALA dairy fat was superior to both the 1.5% ALA palm oil blends for increasing brain DHA (14.4% increase, P<.05), and the 2.3% ALA dairy blend exhibited a further increase that could be ascribed to both an ALA increase and n-6/n-3 ratio decrease. Females had significantly higher brain DHA due to a gender-to-diet interaction, with dairy fats attenuating the gender effect. Brain DHA was predicted with a better accuracy by some plasma and RBC fatty acids when used in combination (R(2) of 0.6) than when used individually (R(2)=0.47 for RBC n-3 docosapentaenoic acid at best). In conclusion, dairy fat blends enriched with ALA appear to be an interesting strategy for achieving optimal DHA levels in the brain of postweaning rats. Human applications are worth considering.

Brain protection by rapeseed oil in magnesium-deficient mice.

Diets given for 30 days with various mono-(MUFA) and poly-(PUFA) unsaturated fatty acid contents were evaluated for brain protection in magnesium-deficient mice: a commercial and three synthetic diets (n-6PUFA, n-3PUFA and MUFA-based chows enriched with 5% corn/sunflower oils 1:3, with 5% rapeseed oil and with 5% high oleic acid sunflower oil/sunflower oil 7:3, respectively). Unlike magnesium deprivation, they induced significant differences in brain and erythrocyte membrane phospholipid fatty acid compositions. n-3PUFA but not other diets protected magnesium-deficient mice against hyperactivity and moderately towards maximal electroshock- and NMDA-induced seizures. This diet also inhibited audiogenic seizures by 50%, preventing animal deaths. Because, like n-6PUFA diet, matched control MUFA diet failed to induce brain protections, alpha-linolenate (ALA) rather than reduced n-6 PUFA diet content is concluded to cause n-3PUFA neuroprotection. Present in vivo data also corroborate literature in vitro inhibition of T type calcium channels by n-3 PUFA, adding basis to ALA supplementation in human anti-epileptic/neuroprotective strategies.

Activities of α-asarone in various animal seizure models and in biochemical assays might be essentially accounted for by antioxidant properties.

Anticonvulsant properties of α-asarone were studied in mice at three doses with different toxicity. The 100mg/kg dose decreased both treadmill performance and locomotor activity, caused hypothermia, and potentiated pentobarbital-induced sleep. The last two effects and no toxicity were observed at 60 and 22mg/kg, respectively. In chemical (pentylenetetrazole, picrotoxin, N-methyl-D-aspartate, pilocarpine) and electrical (maximal electroshock) seizure tests, neither seizures nor death were prevented by 60 mg/kg α-asarone which, however, exhibited protective-like effects (delay in the onset of clonic and/or tonic seizures and/or in the death of mice). Magnesium deficiency-dependent audiogenic seizures responded to non-toxic doses of α-asarone (60 mg/kg and less): 22 mg/kg protecting 50% of tested animals. Because these seizures respond to both anti-seizure and antioxidant compounds, antioxidant properties of α-asarone were studied, indicating 5 Units of superoxide dismutase-like activity per mg α-asarone. Treatment of mice by α-asarone (daily dose of 100mg/kg during 7 days) induced brain antioxidant enzymes (superoxide dismutase, glutathione peroxidase and reductase) in striatum and hippocampus and to a lesser extent in cortex. In view of recent findings about deleterious roles of chronic inflammatory/oxidant stresses in human epilepsy outcome, antioxidant and inductive properties of α-asarone are proposed to be coherent bases for traditional clinical efficacy.

1,2-ethane bis-1-amino-4-benzamidine is active against several brain insult and seizure challenges through anti-NMDA mechanisms targeting the 3H-TCP binding site and antioxidant action.

Five bis-benzamidines were screened towards murine magnesium deficiency-dependent audiogenic seizures, unravelling two compounds with efficacious doses 50 (ED(50)) less than 10mg/kg. They were also screened against maximal electroshock and subcutaneous pentylenetetrazole-induced seizures, and explored for superoxide -scavenging activity. 1,2-Ethane bis-1-amino-4-benzamidine (EBAB) was selected and evaluated in 6 Hz seizure test (ED(50)=49 mg/kg) and at 4 microg/kg in focal cerebral ibotenate poisoning in pups (sizes of both white and grey matter wounds were halved). EBAB was further tested on NMDA-induced seizures in mice (ED(50)=6 mg/kg) and on (3)H-TC -binding to a rodent cerebral preparation (IC(50)=1.4 microM). Taken as a whole, present data emphasise the suitability of bis-benzamidines as templates for designing brain protective compounds.

Experimental stroke protection induced by 4-hydroxybenzyl alcohol is cancelled by bacitracin.

Induction of protein disulfide isomerase (PDI) is validated as a main mechanism by which 4-hydroxybenzyl alcohol (4-HBA), an active principle of Gastrodia elata Blume, reduces cerebral infarct volumes in a murine model of focal brain ischemia/reperfusion. In contrast to its position isomers, i.e. 3-hydroxybenzyl alcohol (3-HBA) and 2-hydroxybenzyl alcohol (2-HBA), and to aliphatic diols (1,4-butanediol and 1,5-pentanediol), 4-HBA administered intravenously at 25 mg/kg protected mice, significantly reducing total, cortical and sub-cortical infarct volumes by 42, 28 and 55%, respectively. All compounds, 4-HBA included, were devoid of antioedematous properties. Only the stroke protective 4-HBA, but neither 3-HBA nor 2-HBA, was capable of significantly inducing PDI in intact mouse brains. Stroke protection was fully prevented by bacitracin (500 mg/kg), a known inhibitor of PDI, which, without affecting basal brain PDI levels, altered the ability of 4-HBA to induce significantly PDI in intact brains. Taken as a whole, our data indicate that stroke protection induced by 4-HBA involves PDI as a key player, making this protein a valuable target to control brain injury disorders. The fact that 4-HBA, at doses up to 200mg/kg, was devoid of neurotoxicity in the rotarod test is also a decisive element to promote the neuroprotective use of this plant compound.

Threshold to N-methyl-D-aspartate-induced seizures in mice undergoing chronic nutritional magnesium deprivation is lowered in a way partly responsive to acute magnesium and antioxidant administrations.

Magnesium deficiency may be induced by a diet impoverished in magnesium. This nutritional deficit promotes chronic inflammatory and oxidative stresses, hyperexcitability and, in mice, susceptibility to audiogenic seizures. Potentiation by low-magnesium concentrations of the opening of N-methyl-D-aspartate (NMDA) receptor/calcium channel in in vitro and ex vivo studies, and responsiveness to magnesium of in vivo brain injury states are now well established. By contrast, little or no specific attention has been, however, paid to the in vivo NMDA receptor function/excitability in magnesium deficiency. The present work reports for the first time that, in mice undergoing chronic nutritional deprivation in magnesium (35 v. 930 parts per million for 27 d in OF1 mice), NMDA-induced seizure threshold is significantly decreased (38 % of normal values). The attenuation in the drop of NMDA seizure threshold (percentage of reversal) was 58 and 20 % upon acute intraperitoneal administrations of magnesium chloride hexahydrate (28 mg magnesium/kg) and the antioxidant ebselen (20 mg/kg), respectively. In nutritionally magnesium-deprived animals, audiogenic seizures are completely prevented by these compound doses. Taken as a whole, our data emphasise that chronic magnesium deprivation in mice is a nutritional in vivo model for a lowered NMDA receptor activation threshold. This nutritional model responds remarkably to acute magnesium supply and moderately to acute antioxidant administration.

The PPARgamma agonist FMOC-L-leucine protects both mature and immature brain.

(N-[9-fluorenylmethoxycarbonyl]-)-L-leucine (FMOC-L-leucine) and rosiglitazone, two ligands of peroxisome proliferator-activated receptor gamma (PPARgamma), were evaluated in mature (adult mice) and immature (pups) brain injury models. In adult magnesium-deficient mice, a model responsive to both neuroprotective and anti-seizure compounds, FMOC-L-leucine, but not rosiglitazone, protected against audiogenic seizures. The protection afforded by FMOC-L-leucine was alleviated by the PPARgamma antagonist GW9662 (1-2 mg/kg) and was induced in 50% animals by 4.8+/-1.2 mg/kg. At this dose, FMOC-L-leucine modified audiogenic seizure phase durations in convulsing mice differently than prototype antiepileptic drugs did. FMOC-L-leucine (up to 100 mg/kg) was inactive in the 6 Hz seizure test, an adult animal model largely responsive to anti-seizure drugs. In a model of neonatal brain injury, FMOC-L-leucine (4 microg/kg) was neuroprotective against cerebral ibotenate toxicity. It reduced significantly the size of lesions in grey but not in white matter, while rosiglitazone (10 microg/kg) was inactive. Taken as a whole, the present data support neuroprotective potentialities of FMOC-L-leucine towards both mature and immature brain. The PPAR-based protection of immature brain is more important as it is known that classic adult brain protectants (GABA(A) activators, N-methyl-D-aspartate and sodium channel blockers) may be toxic for immature brain. The PPARgamma agonist FMOC-L-leucine is likely to be devoid of these classic protective mechanisms because of its inactivity in the 6 Hz seizure test, its activity in the audiogenic test being explained by neuroprotective rather than intrinsic anti-seizure mechanisms. Targeting PPARs might be thus a promising way to protect immature brain.

Headache due to photosensitive magnesium depletion.

Clinical and paraclinical data (visual stress tests, electroencephalographic and cerebrovascular photic driving, visual evoked potentials) demonstrate that the concept of photosensitive headache is fully justified. The interictal hallmark of photosensitive cephalalgic patients is potentiation (or sensitization) instead of habituation. The aetiopathogenic mechanisms of photosensitive headache associate hypofunction of the biological clock and magnesium depletion. The new concept of headache due to photosensitive magnesium depletion seems justified. It appears logical to add the treatments of magnesium depletion and of photosensitivity to classical treatment of headache. Prophylactic magnesium treatment relies on atoxic nutritional magnesium supplementation in case of primary magnesium deficiency. Pharmacological doses of parenteral magnesium may be used but may induce toxicity. Therefore it is necessary to know the therapeutic index of magnesium compound used: the larger its value, the greater the safety margin. Treatment of photosensitivity uses various types of <>: darkness therapy through physiologic, psychotherapic, physiotherapic, pharmacologic stimulating techniques and substitutive darkness therapy through palliative treatment. Melatonin is only a partial substitutive treatment of photosensitivity. A new model of photosensitive magnesium depletion with potentiation should be a useful tool for discriminating the most efficient gent.

Electrical activity alterations induced by chronic absorption of lindane (gamma-hexachlorocyclohexane) trace concentrations in adult rat heart.

The heart of adult rat offspring, born to mothers treated with trace concentrations of lindane (0.5 to 2 ppb) through a beverage and to mothers chronically treated with lindane (CL-T) with the same trace concentration, also through a beverage, during lactation and growth has a round shape and accumulates lindane. The left ventricle (LV) presents a hypertrophied area, atrophied papillary muscles, and unorganized collagen bundles and layers. These observations led us to study the electrical activity of their left ventricle papillary muscles (LVPM) by recording action potential using intracellular microelectrodes. CL-T shortened LVPM action potential duration (APD): 1 ppb shortened the plateau; 2 ppb shortened the plateau and the slow repolarizing phase. In CL-T (2 ppb) and untreated groups, low temperature (22 degrees C) decreased the resting potential and prolonged APD. TEA (tetraethylammonium; 1-2 mmol/L) partially lengthened CL-T (2 ppb lindane) APD. Quinidine (0.2 mmol/L) and E-4031 (10 nmol/L) prolonged CL-T APD, suggesting that the rapid delayed outward K+ current (IKr) was increased. Our results indicate the silent effects of chronic exposure to trace concentrations of lindane on the morphological and electrical activity of heart muscle. They demonstrate that chronic lindane treatment of female rats alters the tissue integrity and electrical activity in the LV of their offspring.

New data on the importance of gestational Mg deficiency.

Chronic primary Mg deficiency is frequent. Around 20% of the population consumes less than two-thirds of the RDA for Mg, in both genders and in women particularly: for example, in France, 23% of women and 18% of men. Primary Mg deficiency may occur in fertile women. Gestational Mg deficiency is able to induce maternal, fetal, and pediatric consequences which might last throughout life. Experimental studies of gestational Mg deficiency show that Mg deficiency during pregnancy may have marked effects on the processes of parturition and of postuterine involution. It may interfere with fetal growth and development from teratogenic effects to morbidity: i.e. hematological effects and disturbances in temperature regulation. Clinical studies on the consequences of maternal primary Mg deficiency in women have been insufficiently investigated. To check the validity of the role of this frequent gestational Mg deficiency, the protocol of a long term multicentric placebo controlled prospective study on the effects of maternal nutritional Mg supplementation on lethality and morbidity in fetus, neonates, infants, children and adults should be carried out not only during pregnancy and the first year of life, but throughout life. Two clinical forms of chronic gestational Mg deficiency in women have been stressed: Premature labor when chronic maternal Mg deficiency is involved in uterine hyperexcitability, Sudden Infant Death Syndrome (SIDS) when it is caused by either simple Mg deficiency or various forms of Mg depletion. Nutritional Mg treatment of premature labor. If gestational Mg deficiency is the only cause for uterine overactivity, nutritional Mg supplementation constitutes the etiopathogenic atoxic tocolytic treatment. But although it is an adjuvant factor in premature labor, it is only a useful accessory treatment, devoid of toxicity but which increases the effectiveness and safety of the associated tocolytic drugs such as beta-2 mimetics. SIDS due to gestational Mg deficit: Mg deficiency or various forms of Mg depletion. SIDS may be caused by the fetal consequences of maternal Mg deficiency through an impaired control of Brown Adipose Tissue (BAT) thermoregulation, mechanisms leading to a modified temperature set point. SIDS may result from dysthermias: hypo- or hyperthermic forms. A possible prevention could rest on simple maternal nutritional Mg supplementation. Various stresses in pregnant women or in the infant may transform a simple Mg deficiency into Mg depletion: stress in baby care such as bedding in prone position, environmental factors such as parental smoking, but the role of chronopathological stress particularly appears to be too often neglected as it constitutes a clinical form of primary hypofunction of the biological clock [with its anatomical and clinical stigma such as reduced production of melatonin (MT) and of its urinary metabolite: 6 Sulfatoxy-Melatonin (6 SMT)]. SIDS might be linked to an impaired maturation of both the photoneuroendocrine system and BAT. A preventive treatment of this form of SIDS should associate atoxic nutritional Mg therapy for pregnant women with total light deprivation at night for the infant. The place of Mg therapy for the infant and of MT, L Tryptophan and taurine is uncertain for the moment.

Magnesium research: from the beginnings to today.

The beginnings of magnesium research, from the 18th century to the first quarter of the twentieth century, consists mainly of the development of chemical and pharmacological knowledge. The modern period began in 1926 when the essential character of magnesium was acknowledged. The early part of the modern period, up to the 1960s, saw the foundation of our knowledge of the basic physiological, epidemiological and clinical aspects. The present modern period began in 1971 with the First International Symposium on Magnesium and the subsequent creation of SDRM (the international Society for the Development of Research on Magnesium), an international coordinating structure, which promotes the publication of magnesium books (volumes of proceedings and monographs) and of journals: Magnesium Research the international official organ of SDRM and several national journals: the Journal of Japanese Society for Magnesium Research (Japan), the Buletin informativ al societatii romane de cercetare a magneziului (Romania), the Journal of Elementology (Poland) and which regularly organizes national and international meetings. The next great international meeting will be held on October 23-26, 2006 in Osaka (Japan). We will discuss the latest research findings on magnesium in health and disease. The subject shows that today magnesium research remains active in basic sciences and embraces all the facets of pathology.

Beta-2 mimetics and magnesium: true or false friends?

Physiological beta stimulation may be involved in the regulation of magnesium status namely by homeostatic increase of magnesemia during magnesium deficiency. But conversely excessive beta stimulation namely by use of pharmacological high doses of beta mimetics may induce a decrease of magnesemia. Two different types of magnesium therapy ought to be distinguished. Nutritional magnesium therapy which may physiologically palliate a magnesium deficiency due to an insufficient magnesium intake. It is devoid of any toxicity. Pharmacological magnesium therapy, whatever the magnesium status, causes a iatrogenic magnesium load. It may induce magnesium toxicity. Tocolysis is the one common obstetrical indication for beta mimetics and magnesium. Beta-2 mimetics are the reference tocolytic drugs in most countries. But high doses of beta-2 mimetics for suppression of premature labor are associated to a high incidence of maternal, fetal and neonatal side effects. Tocolysis must then be discontinued or limited to shorter treatments with the lowest possible doses. Nutritional magnesium therapy which palliates gestational magnesium deficiency is efficient and atoxic. Conversely, high doses of intravenous MgSO4 for tocolysis are less efficient and unsafe. Because of its maternal and above all pediatric side effects, this maternal pharmacological magnesium therapy should be abandoned for tocolysis. Investigation of the therapeutic ratio of various magnesium salts before their clinical use could help to determine if other anions different from sulfate could decrease the toxicity. Beta-2 agonists are first line asthma therapy, but their safety is debated. Asthma and Chronic Obstructive Pulmonary Disease (COPD) per se may induce magnesium depletion related to a dysregulation of the control mechanisms of magnesium status. It requires a correction of its causal regulation, but nutritional magnesium supplementation is ineffective. When chronic primary magnesium deficiency coexists with obstructive bronchial disorders, it constitutes a decompensatory factor. Atoxic nutritional magnesium therapy may palliate this coexistent magnesium deficiency. Pharmacological magnesium treatment for obstructive pulmonary diseases is not very efficient with low safety. Combination of palliating nutritional magnesium therapy and of beta-2 mimetics for tocolysis or pulmonary obstructive indications may be beneficial and remain atoxic. Conversely combination of intravenous tocolytic high doses of magnesium and of beta-2 mimetics is contra-indicated because of its dubious efficiency and its possible toxicity. The possible role of SO4- as regards toxicity must be discussed. Contra-indications of lower intravenous or inhaled Mg doses for pulmonary bronchial obstruction are less imperative than for tocolysis. The selection of a particular magnesium salt among others should take into account reliable plasmacological and toxicological data. It seems necessary to determine the therapeutic ratio (LD50/ED50) of the various available magnesium salts before pharmacological use.

THC aggravates rat muricide behavior induced by two levels of magnesium deficiency.

A severe magnesium deprivation induces an interspecific aggressive behavior (muricidal behavior, MB) in different strains of rats. Delta9-tetrahydrocannabinol (THC) is also known to induce MB even after a single injection (11 mg/kg) in starving, isolated rats. In the present work, we investigated the MB behavior, for six successive assays 1 h delayed, of two groups of male Long-Evans rats fed 50- or 150-ppm Mg(2+)-deficient diets, for 42 days after a single injection of THC at doses (2, 4 or 8 mg/kg) that did not induce aggressiveness in control rats. This treatment led to Mg(2+) plasma levels of 5+/-0.3 and 12.3+/-0.9 mg/ml vs. 21+/-1.5 mg/ml initially. In the 50-ppm Mg-deficient rat group, all the rats were muricidal but the MB pattern was severely aggravated by THC. In the 150-ppm Mg-deficient rat group, no rat was muricidal but all doses of THC induced a 100% MB. In addition, by quantifying the three phases of MB, we showed through six consecutive hourly muricidal assays, that the two first phases (attack latency and attack on the living mouse) decreased progressively, whereas the third phase (attack on the dead mouse) increased dramatically. This indicates firstly that Mg-deprivation decreases the responsiveness threshold of rats to THC. Secondly, these very low doses of THC induced an aggravation of MB and an acquired hyper-aggressiveness in both 50- and 150-ppm Mg-deficient rats, probably involving different neurotransmitters, mainly serotonin, which is decreased by both treatments.

Does lindane (gamma-hexachlorocyclohexane) increase the rapid delayed rectifier outward K+ current (IKr) in frog atrial myocytes?

BACKGROUND: The effects of lindane, a gamma-isomer of hexachlorocyclohexane, were studied on transmembrane potentials and currents of frog atrial heart muscle using intracellular microelectrodes and the whole cell voltage-clamp technique. RESULTS: Lindane (0.34 microM to 6.8 microM) dose-dependently shortened the action potential duration (APD). Under voltage-clamp conditions, lindane (1.7 microM) increased the amplitude of the outward current (Iout) which developed in Ringer solution containing TTX (0.6 microM), Cd2+ (1 mM) and TEA (10 mM). The lindane-increased Iout was not sensitive to Sr2+ (5 mM). It was blocked by subsequent addition of quinidine (0.5 mM) or E-4031 (1 microM). E-4031 lengthened the APD; it prevented or blocked the lindane-induced APD shortening. CONCLUSIONS: In conclusion, our data revealed that lindane increased the quinidine and E-4031-sensitive rapid delayed outward K+ current which contributed to the AP repolarization in frog atrial muscle.

Biorhythms and possible central regulation of magnesium status, phototherapy, darkness therapy and chronopathological forms of magnesium depletion.

Biological clock and magnesium status are linked. Central magnesium regulation may be hypothetized. Balanced magnesium status is requested to obtain efficiency of suprachiasmatic nuclei and of pineal gland. Conventional bright light therapy appears as a speedy and efficient antidepressant medication useful for the treatment of various types of depression, and of non migrainous headaches also. Although decrease in melatonin production seems accessory, increases of serotonergy and perhaps of Reactive Oxygen Species constitute the main mechanisms of action. Chromatotherapy emphazizes the effects of short exposure to specific colors. Although the increased production of melatonin constitutes the best marker of darkness, it is only an accessory mechanism of its action. The psycholeptic sedative effects of darkness, like those of magnesium, rely on direct membraneous and oxidant actions, neural mediated effects (i.e. stimulation of inhibitory neuromodulators such as GABA and taurine), and on antagonism of neuroactive gases (CO and NO). Darkness therapyper se, partial substitutive therapy with melatonin and with their mimicking agents (Mg, L-Tryptophan,Taurine) apply to all the chronopathological forms of magnesium depletion with decreased production of melatonin: sleep disorders, migraine, chronic fatigue syndrome, fibromyalgia, some forms of asthma and of sudden infant death syndrome. Further research should assess the importance of the chronopathological forms of magnesium depletion in the physiopathology of these disorders.

[Reproductive toxicity of lindane]. / Toxicité du lindane sur la reproduction.

The present paper bears on the main effects of lindane (gamma isomer of hexachlorocyclohexane) on endocrine and reproductive functions in mammals. This pesticide, once widely used to kill lice and a variety of pests that attack agricultural products, livestock and trees, has been progressively eliminated from many applications since the mid-1970s in Europe or USA, but is still used in the rest of the world. Lindane is absorbed through respiratory, digestive or cutaneous routes and accumulates in fat tissues. It damages human liver, kidney, neural and immune systems and induces birth defects, cancer and death. Chronic administration results in endocrine disruption in birds as well as in mammals. Treatment with 1-40 mg of lindane/kg b.w. disrupts testicular morphology, decreases spermatogenesis, inhibits testicular steroidogenesis, reduces plasma androgen concentrations and may adversely affect reproductive performances in males. In females, lindane disrupts the estrous cycle, reduces serum estrogen and progesterone levels, decreases sexual receptivity whereas in pregnant dams it decreases whelping rate and litter size. These effects were also observed in some rats exposed to residual environmental doses. In addition, there is concern that irreversible effects may be induced when animals are exposed to endocrine disrupting chemicals during critically susceptible phases of sexual differentiation or development. These effects would results from (i) alterations of gonade or gamete cell membranes (ii) cell metabolism changes including alterations of ionic exchanges (mainly calcium or potassium), direct or free radical-mediated inhibition of steroidogenesis (iii) or neuroendocrine changes leading to a decrease in sexual performance of either parents or their offsprings exposed in utero or through lactation.

[Cardiotoxicity of lindane, a gamma isomer of hexachlorocyclohexane]. / Cardiotoxicité du lindane, un isomère gamma de l'hexachlorocyclohexane.

The goal of the present review is to collect information concerning membrane effects induced by lindane intoxication, a y isomer of hexachiorocyclohexane (gamma-HCH) that has been largely used as an insecticide and disinfectant in agriculture and entered also in the composition of some lotions, creams and shampoos used against parasites (lice and scabies). Absorbed through respiratory, digestive or transcutaneous pathways, lindane accumulates within lipid rich tissues. Lindane accumulation depends on the duration of the exposure and affects tissues in the following order: adipose tissues > brain > kidney > muscle > lungs > heart > liver > blood. Whatever the mode of lindane absorption, it accumulates in blood and is distributed throughout the body. It may affect human health by exerting systemic, immunologic, teratogenic, and/or cancerogenic effects. The symptoms of lindane intoxication are different according to the mode of intoxication, acute or chronic. The absorption of high doses of gamma-HCH is particularly toxic for the central nervous system and for the female and male reproduction apparatus in mammals where lindane is considered as an endocrine disruptor. Lindane is highly lipophilic and incorporates into biological membranes according to the following sequence: mitochondria > sarcoplasmic reticulum > myelin > brain microsomes > erythrocytes. Lindane exerts a stimulating action on synaptic transmission and inhibits the chloride current activated by gamma-amino butyric acid (GABA) of many muscular and nervous preparations by interacting with the receptors GABA-chloride channel complex. It seems to affect calcium homeostasis of many tissues. The similarity between lindane and inositol (1, 4, 5) phosphate (IP3) suggested that lindane releases Ca2+ from IP3-sensitive intracellular stores in macrophages and myometrial cells. Ca2+ release from reticulum endoplasmic, mitochondria and other Ca2+ stores has been reported in cat kidney cells. Lindane altered energetic metabolism of hepatic mitochondria and the inositol-phosphate synthesis in neuronal cells. However, lindane does not compete with the IP3 receptor. Lindane produces a Ca2+ influx in mice peritoneal macrophage cells responsible for the Ca2+ induced Ca2+ release produced by phospholipase C via IP3 pathway and resulting in a maintained increase of the free cytosolic Ca2+ concentration. Lindane decreased the membrane erythrocyte and cerebral cell concentration of phosphatidyl inositol PI, PIP and PIP2 in rats repetitively exposed to lindane for 3 or 6 months. Lindane induces oxidative stress; it modifies the activity of the scavenger enzymes. This effect is involved in the inhibition of intercellular gap junctions. Modifications of the electrocardiogram (ECG), sinusal rhythm alteration and negative and dysphasic variations of T wave, similar to those produced by hyperkaliemia, have been reported after lindane absorption. During acute lindane poisoning, the activities of serum transaminases (SGOT, SGTP), and lactate deshydrogenase (LDH) increase. Lindane produces histological alterations of cardiac tissues and a cardio-vascular dystrophy (contracture, degenerescence and necrosis) mainly in the left ventricular wall and a hypertrophy of the left ventricle. Chronic application of residual doses of lindane shortened the action potential duration in rat papillary muscle. These effects were similar to those induced by hyperthyroidism. Lindane increases the triiodothyronine (T3) serum level in hyperthyroid rats. T3 plays an important role in the postnatal development of the rat ventricle by increasing the density of potassium channels which contribute to action potential shortening during the development. Thyroid hormones influence the regulation and the expression of messengers ARN which encode different potassium channels involved in action potential repolarization (Kvl.2; Kvl.4; Kvl.5; Kv2.1; Kv4; HCN2). The thyrotropine-releasing hormone (TRH) modulates the HERG-type rapid delayed potassium channel (IKr) encoded by the human gene ether-a-go-go in rat anterior pituitary cells GH3/B6. This channel is involved in the cardiac long QT syndrome. TRH modifies the current kinetics of human HERG potassium channel co-expressed in Xenopus oocytes with the TRH receptor, whose activity is modulated via the protein kinase C pathway linked to a G protein-coupled receptor and is regulated by changes in the PIP2 concentration in the membrane. IKr channels regulation is also dependent on sexual hormones. In conclusion, lindane affects the excitable membranes and the cardio circulatory system. These alterations (may) represent a potential risk for human health.