[A Nematode Nobel Prize: Caenorhabditis elegans]. / Un Nématode Prix Nobel: Caenorhabditis elegans.

The Nematode Caenorhabditis elegans (C. elegans) is an established model increasingly used for studying human disease pathogenesis. C. elegans models are based on the mutagenesis of human disease genes conserved in this Nematode or on the transgenesis with disease genes not conserved in C. elegans. Genetic examinations will give new insights on the cellular and molecular mechanisms that are altered in some neurodegenerative diseases like Duchenne's muscular dystrophy, Huntington's disease and Alzheimer's disease. C. elegans may be used for primary screening of new compounds that may be used as drugs in these diseases.

Prevention by Ginkgo biloba extract (EGb 761) and trolox C of the decrease in synaptosomal dopamine or serotonin uptake following incubation.

Prolonged incubation of synaptosomes in Krebs-Ringer oxygenated medium in the presence of ascorbic acid (10(-4) M) led, after 20 min, to a decrease in [3H]dopamine (DA) (synaptosomes prepared from the striatum) and [3H]serotonin (5HT) (synaptosomes prepared from the cortex) uptake. The decrease was progressive and uptake was virtually abolished after a 60 min incubation period. A concentration-dependent (from 5 x 10(-6) M) role of ascorbic acid in the decrease of [3H]DA or [3H]5HT uptake was demonstrated. This decrease was potentiated by Fe2+ ions and prevented by the ferrous chelating agent desferrioxamine. Thus, the progressive decrease in synaptosomal uptake of either [3H]DA or [3H]5HT could depend on the generation of free radicals by the association of ascorbic acid with Fe2+ ions. The decrease in synaptosomal uptake was prevented, in a concentration-dependent manner, by the Ginkgo biloba extract EGb 761 (4-16 micrograms/mL) and the vitamin E analog trolox C (10(-4) M). The terpenic fraction of EGb 761, Bn 52063 (up to 0.5 microgram/mL), did not prevent the reduction of [3H]amine uptake. In contrast, the flavonoidic fraction, Cp 202, was effective (from 1 microgram/mL) and its efficacy was shared by the flavonoid quercetin (from 0.1 microgram/mL). The prolongation of the ability of synaptosomes to take up [3H]amine elicited by EGb 761, in particular its flavonoidic fraction, as well as by trolox C could be due to their free radical scavenger properties.

THIP inhibits feeding behavior in fasted rats.

The effects of 4,5,6,7-tetrahydroisoxazolo-[5,4-c]pyridin-3-ol (THIP) were compared with those of d-amphetamine and GABA in fasted rats. Intravenously-administered THIP produced a dose-dependent decrease in food consumption (ED50 congruent to 1.5 mg/kg) by an action that was not reversed by prior subcutaneous or simultaneous intravenous (IV) injection of bicuculline. d-Amphetamine-SO4 also produced a decrease in food consumption in this model (ED50 congruent to 0.2 mg/kg, IV). Unlike THIP, GABA (in doses up to 100 mg/kg, IV) did not produce a marked anorexigenic effect. These results provide further evidence that THIP can penetrate the "blood-brain barrier", and that central GABA-ergic systems are involved in controlling food intake.

Competitive inhibition of 5-HT receptors in rabbit isolated aorta by the Ca(2+)-antagonist methoxyverapamil (D 600).

Experiments conducted with rabbit isolated aorta have revealed that the Ca(2+)-antagonist 3-methoxy-verapamil (D 600) is a potent competitive antagonist of the contractile action of 5-HT. Thus, the anti-hypertensive action of D 600, as well as some of its side effects, could be related to its antagonism of 5-HT receptors. D 600 might be useful in neurochemical and neurophysiological experiments that are aimed at examining 5-HT receptors, as well as in treating certain cerebrovascular disorders of man (e.g., migraine).

Effects of Ginkgo biloba extract (EGb 761) on learning and possible actions on aging.

A study of the effect of Ginkgo biloba extract (EGb 761) has shown enhancing effects on training in adult and aged Swiss mice. An analysis of inbred mice has confirmed this sensitivity to EGb 761, but depending on the strains, with different effects at different ages. The most interesting results are related to improvements in performances observed with aged mice of the DBA/2J strain. The results obtained with inbred strains in the study of the mossy fibers of the hippocampus make it possible to suggest a link between the improvements in training and the histological structure of the hippocampus. This possibility, which can be confirmed by further studies, is presented here.

Effects of the specific platelet-activating factor antagonists, BN 52021 and BN 52063, on various experimental gastrointestinal ulcerations.

Platelet-activating factor (PAF) has been shown recently to induce gastrointestinal damage similar to that evoked by endotoxin, suggesting that the autacoid could be implicated in other types of gastrointestinal damage. Thus, the effects of BN 52021 and BN 52063, two specific PAF antagonists, were investigated in various experimental models of gastrointestinal damage in rats. BN 52021 and BN 52063, markedly reduced both the PAF- and endotoxin-induced alterations of the mucosa, suggesting a role for the autacoid in the latter process. BN 52021 and another unrelated PAF antagonist, triazolam, partially reduced the restraint-stress-induced gastric damage in young female, but not male, rats. Similar partial protection was obtained in rats with ethanol-induced gastric damage. In contrast with atropine and ranitidine, BN 52021 did not affect the gastric hypersecretion in pylorus-ligated rats nor the aspirin-induced gastric ulcerations. The present results indicate that PAF plays a major role in the gastric damage induced by endotoxin and may also partially contribute to the gastric lesions induced by ethanol and stress. The results suggest that there is a potential therapeutic use for PAF antagonists in certain types of gastrointestinal lesions in man.

Antipsychotic drugs depress acetylcholine release in the Torpedo electric organ, a purely cholinergic system.

We used the electric organ of Torpedo, a modified neuromuscular system, to investigate the direct effects of antipsychotic drugs on cholinergic transmission. All the antipsychotic drugs tested inhibited transmission by decreasing the amount of ACh released by nerve impulses. Their potency for this action was as follows: trifluoperazine less than clozapine less than thiethylperazine less than droperidol less than haloperidol less than chlorpromazine = beta-flupentixol less than alpha-flupentixol. Depression of ACh release by antipsychotics was poorly reversible, and was not mediated by dopamine receptors in this system since neither dopamine nor apomorphine had any effect on transmission. Antipsychotics did not act through presynaptic cholinergic receptors since the effect was not antagonized by atropine or quinuclidinyl benzilate. Trifluoperazine had no effect on the total ACh content of the tissue, on the compartmentation of ACh inside and outside synaptic vesicles, or on the rate of ACh turnover or the accumulation of 45Ca observed after repetitive stimulation. We conclude that antipsychotic drugs depress the neurally evoked release of ACh by acting directly on the releasing mechanism.

Role of endothelium on phenylephrine-triggered contractile events in aorta of spontaneously hypertensive rats.

The ability of basal release of endothelium derived relaxing factor (EDRF) to alter contractile events in phenylephrine (PE)-triggered contraction was tested on ring segments of the thoracic aorta removed from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). In normal medium, PE (1 microM) elicited similar whole contractions in endothelium denuded arteries of SHR and WKY. The presence of endothelium only reduced the WKY response. On aorta incubated in a Ca2+ free-medium, PE (1 microM) induced an initial phasic contraction due to intracellular Ca2+ release. This was followed by a tonic contraction after Ca2+ (2.5 mM) was restored to the bath. This sustained contraction was dependent on extracellular calcium influx. Identical phasic and tonic contractions were observed in endothelium denuded rings of SHR and WKY. However, the presence of endothelium only reduced the sustained contraction of WKY arteries. When experiments were carried out in medium containing D600 (1 microM), the presence of endothelium diminished the whole contraction of both SHR and WKY rings whereas the sustained but not the phasic contractions of WKY was also inhibited. This inhibitory effect of endothelium on WKY sustained contraction was significantly higher in the presence of D600. The calcium antagonist reduced both the whole and the tonic contractions of all preparations but was ineffective on the phasic one. The D600 inhibitory action on the sustained contraction was more pronounced in denuded SHR rings than in the corresponding WKY arteries. Thus it is concluded that there is a basal influence of endothelium in both SHR and WKY. Under our conditions, the endothelial function inhibited the extracellular Ca2+ influx and especially the part of Ca2+ influx insensitive to D600. This part of Ca2+ influx is diminished in SHR and thus the efficacy of endothelium products (e.g. EDRF) is reduced in this strain.

Prevention by a Ginkgo biloba extract (GBE 761) of the dopaminergic neurotoxicity of MPTP.

In mice implanted subcutaneously with osmotic minipumps releasing the neurotoxic agent N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) for 7 days (105 micrograms h-1/mouse) (approximately 100 mg kg-1 day-1) a significant reduction (approximately 25%) in the striatal dopaminergic nerve endings was observed. This neurotoxic effect was prevented by the semi-chronic ingestion of a Ginkgo biloba extract for 17 days (GBE 761, approximately 100 mg kg-1 day-1). The high concentrations (approximately 1 g L-1) at which GBE 761 in-vitro either prevented the uptake of [3H]dopamine by synaptosomes prepared from striatum, or prevented the specific binding of the pure dopamine uptake inhibitor [3H]GBR 12783 to membranes prepared from striatum suggests that the prevention of the MPTP neurotoxicity does not depend on an inhibition of the MPTP uptake by dopamine neurons. This is also suggested by the lack of prevention of the in-vitro striatal binding of [3H]GBR 12783 administered i.v. at a tracer dose, in mice pretreated for 8 days with GBE 761 (100 mg kg-1 p.o.) and receiving a supplementary gastric administration of GBE 761 (100 mg kg-1) 1 h before testing. Similar treatment with GBE 761 did not modify the toxicity for dopamine neurons of 6-hydroxydopamine (20 micrograms) directly injected into the striatum of rats.

The Ginkgo biloba extract, EGb761, increases synaptosomal uptake of 5-hydroxytryptamine: in-vitro and ex-vivo studies.

The Ginkgo biloba extract (EGb 761) added to a synaptosomal fraction prepared from mice cerebral cortex modified [3H]5-hydroxytryptamine ([3H]5-HT) uptake in a biphasic manner. Between 4 and 16 micrograms mL-1 EGb 761 increased significantly the [3H]5-HT uptake (maximum + 23%). A similar increase was also obtained when synaptosomes were prepared from the cortex of mice treated orally with EGb 761, either acutely (100 mg kg-1, 14 h and 2 h before death) or semi-chronically (2 x 100 mg-1 kg daily for 4 consecutive days). The in-vitro increase in [3H]5-HT uptake induced by EGb 761 was not observed in the presence of 10(-6) M clomipramine, a 5-HT-uptake inhibitor. EGb 761 did not increase [3H]dopamine uptake by synaptosomes prepared from striatum of mice. We investigated different fractions of EGb 761 in order to determine the compounds inducing the increase in [3H]5-HT uptake. The BN 52063 extract (corresponding to the EGb 761 devoid of flavonoid substances) did not increase [3H]5-HT uptake. The Cp 202 extract (corresponding to the EGb 761 devoid of terpenic substances and containing mostly flavonoid substances) increased [3H]5-HT uptake. Among the flavonoids, quercetin has been tested and had no effect on the [3H]5-HT uptake. Since at the usual therapeutic doses of EGb 761, the effective concentrations of the components responsible for this increase are likely to be reached in the brain, one may suggest that this effect could contribute to the therapeutic effect of EGb 761.

Effects of BN 52063 and other agents inhibiting platelet-activating factor-induced contractile responses in rat portal vein.

Platelet-activating factor (PAF-acether) is a potent agonist (EC50: 3.2 x 10(-8) M) of isolated rat portal vein. BN 52063 (composed of BN 52020, BN 52021 and BN 52022; molar ratio 2:2:1) specifically inhibits PAF-acether (10(-7) M) induced tone (IC50: 3.9 x 10(-5) M). Salbutamol (IC50: 3.1 x 10(-7) M), forskolin (IC50: 3.1 x 10(-6) M) and theophylline (IC50: 2.25 x 10(-4) M) are also effective in inhibiting PAF-acether-induced contractile responses and all excepting forskolin, show a certain specificity in this action. The basal myogenic activity of the rat portal vein is dose-dependently decreased by salbutamol (IC50: 1.2 x 10(-7) M), forskolin (IC50: 2.6 x 10(-6) M) and theophylline (IC50: 2.3 x 10(-4) M) whereas BN 52063 has no effect. The data suggest that rat portal veins possess specific PAF-acether receptors sensitive to BN 52063 and that PAF-acether effects could be inhibited by compounds which can bypass these putative receptors and modulate cAMP levels.

General pharmacology of cicletanine.

Cicletanine is a new antihypertensive molecule which acts directly on vascular smooth muscle by increasing prostacyclin synthesis and interacting with various agents which mobilize intracellular Ca2+ ions. General pharmacological studies have shown that in the anaesthetized normotensive dog, cicletanine does not induce tachycardia (even at high doses) and does not modify aortic, femoral or coronary blood flow. Moreover, cicletanine shows a protective effect on vascular permeability and capillary hyperpermeability. This protective action on the vascular wall is of importance, since one of the direct vascular consequences of arterial hypertension is a fragilisation of vessel walls, tissue oedema and even vascular rupture. Cicletanine slows down the thrombogenic process initiated by electric arterial stimulation. Retardation of the thrombogenic process by the drug may be explained by the stimulation that cicletanine exerts on the synthesis and production of prostacyclin. Behavioural studies in mice, rats and primates have shown that cicletanine has no sedative effects, even at very high doses. General pharmacological studies have demonstrated that both cardiovascular function and the central nervous system are equally tolerant to cicletanine. Cicletanine is an antihypertensive agent which has no effect on cardiovascular haemodynamics and is able to prevent some rheological and vascular-linked cardiac risks of hypertension.

Comparison of cicletanine with other antihypertensive drugs in SHR-SP models.

The effects of cicletanine were compared with those of four other antihypertensive drugs (prazosin, a highly selective alpha 1 antagonist; captopril, an angiotensin-converting enzyme inhibitor; indapamide, an antihypertensive diuretic; and hydrochlorothiazide, a purely diuretic agent) on young stroke-prone SHR rats with high-salt diet. All the drugs except hydrochlorothiazide prevented the onset of hypertension. The minimal effective dose on blood pressure was 1 mg/kg for both cicletanine and captopril, and 3 mg/kg for indapamide. The action on cardiac hypertrophy and diuresis occurs at a dose of cicletanine 10 to 30 times higher than that required to produce the antihypertensive effect. Renal hypertrophy was also decreased significantly by cicletanine at a dose of 100 mg/kg.

In vivo and in vitro effects of cicletanine in spontaneously hypertensive rats.

Oral treatment for 2 weeks with cicletanine [1,3-dihydro-6-methyl-7-hydroxy-3-(4-chloro-phenyl)furo(3,4-c)pyridine] at 30 mg/kg/day delayed the onset of hypertension in spontaneously hypertensive rats (SHR) (15.7 mmHg, p less than 0.001). This antihypertensive effect was increased when the animals were maintained on a high-salt diet (40.8 mmHg, p less than 0.001). The ability of cicletanine to alter calcium movements in phenylephrine (PE)- and angiotensin II (ANGIO)-triggered contraction was tested on isolated SHR aorta. PE (1 microM) and ANGIO (0.1 microM) induced a phasic contraction in calcium-free medium due to intracellular calcium release. Upon addition of calcium (2.5 mM) a second sustained (PE) or biphasis (ANGIO) contraction was observed. This second contraction was dependent on extracellular calcium influx. Cicletanine (0.1-0.3 mM) both reduced the phasic (77%, p less than 0.001 for PE; 68%, p less than 0.05 for ANGIO with cicletanine 0.3 mM) and the second contraction elicited by the two agonists (27%, p less than 0.001 for PE; 84%, p less than 0.001 for ANGIO with cicletanine 0.3 mM). These results suggest that in addition to its stimulatory effect on prostaglandin, a direct vascular action of cicletanine could also be involved in the antihypertensive properties of the drug.

In vitro cardiovascular antihistamine properties of cicletanine in comparison with diphenhydramine.

Cicletanine (CIC) (pA2: 7.0) was found to be as potent as diphenhydramine (DIPH) (pA2: 7.2) in competitively inhibiting histamine-induced contraction of isolated rabbit aorta. Both CIC (pA2: 7.3) and DIPH (pA2: 7.5) similarly shifted histamine-induced endothelium-dependent relaxation of isolated rat aorta to the right. The similarity of results (in terms of pA2 values) indicates that in spite of their opposite responses on vascular tone, the H1 receptors on rabbit and rat aortae may be similar. DIPH was found to be as potent as cocaine in potentiating the chronotropic action of noradrenaline on isolated right atria, whereas CIC was without effect. The ability of DIPH to inhibit the noradrenaline uptake at the neuronal membrane seems to be independent of its H1-receptor antagonism potency. Finally, the furopyridine framework of CIC does not elicit the cocaine-like activity of the oxyethylamine residue of DIPH.

In vivo anti-allergic and anti-inflammatory effects of drugs that inhibit lipoxygenase activity in vitro.

Studies in vitro have already shown that the chemotactic effect of leukotriene LTB4, as well as its pro-aggregatory effect on a suspension of leukocytes, could be inhibited by the lipoxygenase (LO) inhibitor ETYA; moreover a beneficial effect of another LO-inhibitor, diethylcarbamazine, has been shown on experimental asthma. To explore a possible therapeutic application of substances that inhibit 15-LO of soybean in vitro, we have tested several active compounds, namely nordihydroguaiaretic acid (NDGA), phenidone, diethylcarbamazine and mefenamic acid, on the following in vivo inflammation models in the rat: plantar oedema induced by carrageenin; cutaneous vascular hyperpermeability induced by pafacether; pleurisy induced by carrageenin. The correlation between the LO-inhibitor effect of these compounds in vitro and their beneficial effects in the different tests that were performed, as well as the mechanisms of action induced in the different experimental models, are discussed.

[Protective effects of a Ginkgo biloba extract (EGb 761) on ischemia-reperfusion injury]. / Effets protecteurs de l'extrait de Ginkgo biloba (EGb 761) sur les lésions tissulaires de l'ischémie-reperfusion.

EGb 761 is a standardized extract of dried leaves of Ginkgo biloba. EGb 761 is a neuroprotective and anti-ischaemic drug. Its broad spectrum of pharmacological activities allows it to be adequate to the numerous pathological requirements--haemodynamic, haemorrheological, metabolic--which occur in cerebral, retinal, cochleovestibular, cardiac or peripheral ischaemia. Moreover, EGb 761 has direct effects in retinal and myocardial ischaemia and reperfusion injuries. EGb 761 improves retinal microcirculation, reduces oedema of the retinal inner layer and protects chemoreceptors against free-radical injuries. On myocardial ischaemia-reperfusion models, EGb 761 improves myocardial functional recovery, and reduces the number of ventricular extrasytoles and the duration of ventricular tachycardia induced by reperfusion. EGb 761 protects the retina and the heart against ischaemia-reperfusion damage via its free radical-scavenging and anti-lipoperoxidative properties and its regulation of mitochondrial respiratory function.

[From the body to the cell membrane: the different levels of pharmacological action of Ginkgo biloba extract]. / De l'organisme aux membranes cellulaires: les différents niveaux d'actions pharmacologiques de l'extrait de Ginkgo biloba.

The pharmacological study of Ginkgo biloba extract has required numerous experiments over several years: different pathological models of cerebral ischaemia to evaluate its effects, and experiments at both cellular and molecular levels to determine its mechanisms of action. In experimental models of ischaemia, oedema and hypoxia, Ginkgo biloba extract reduced vascular, tissular and metabolic disturbances as well as their neurological and behavioural consequences. The pharmacological effects of Ginkgo biloba extract concern vascular, rheological and metabolic processes. Several membrane mechanisms seem to be involved: protection of the membrane ultrastructure against free radicals, modulation of some enzymatic systems and ionic pumps. The originality of the pharmacological properties of Ginkgo biloba extract lies in preferential focusing of its effects on ischaemic areas.

[Mechanism of action of Ginkgo biloba extract in experimental cerebral edema]. / Mécanismes d'action de l'extrait de Ginkgo biloba sur l'oedème cérébral expérimental.

Oedema is one of the major complication of cerebral ischaemia being at the same time a consequence and an aggravating factor. Its first phase is intracellular and cytotoxic, with breakdown of ionic pumps through loss of energy, resulting in a whole sequence of ionic perturbations characterized by loss of intracellular K+ and accumulation of water and Na+, Cl-, and Ca2+ ions in the cells of the ischaemic zone. The second phase, termed vasogenic, applies to the accumulation of lactates, inorganic phosphates and free polyunsaturated fatty acids and in particular, arachidonic acid. This last compound is responsible for the production of membrane "aggressors", amongst which free radicals play an important rôle. Ginkgo biloba extract limits the formation of cerebral oedema and suppresses its neurological consequences, whether the oedema is of cytotoxic (triethyltin) or vasogenic (unilateral traumatic oedema) origin. Several membrane mechanisms could be implicated in the protective action manifested by Ginkgo biloba extract against cerebral oedema.

[Effects of Ginkgo biloba extract on a cerebral ischemia model in gerbils]. / Effets de l'extrait de Ginkgo biloba sur un modèle d'ischémie cérébrale chez la gerbille.

Certain anatomical characteristics peculiar to the gerbil make it the animal model best adapted to experimental pathology studies of acute ischaemia. In this animal species, devoid of any substitute vertebro-basilar vascular tissue, unilateral ligature of the carotid artery produces a cerebral ischaemia with neurological signs (well quantifiable), metabolic perturbations (especially mitochondrial) and cerebral oedema development closely resembling the symptoms revealed by physiopathology in human clinical studies. Using this model and under the experimental conditions described, clear-cut, highly significant results were obtained with Ginkgo biloba, whether by oral or intravenous administration. These results were normalization of mitochondrial respiration, diminution of cerebral oedema, correction of the accompanying ionic perturbations, and practically total functional restoration revealed by a normal neurological index in the gerbils treated with Ginkgo biloba extract.