Electrophysiological effects of bepridil and its quaternary derivative CERM 11888 in closed chest anaesthetized dogs: a comparison with verapamil and diltiazem.

1. The electrophysiological effects of bepridil, its quaternary derivative, CERM 11888 (methylpyrrolidinium bromide) (both 2.5 mg kg-1 i.v.) and those of verapamil and diltiazem (0.2 mg kg-1 i.v.) were studied in closed chest anaesthetized dogs at doses used in clinical studies. 2. The four drugs caused a bradycardia with the following order of potency: bepridil greater than CERM 11888 greater than diltiazem greater than verapamil. 3. All the compounds slowed conduction in the AV node, increased the refractory period (RP) and decreased Wenckebach rates with the following order: verapamil much greater than diltiazem greater than bepridil greater than CERM 11888. 4. Verapamil and diltiazem did not affect conduction or the RP in atria while bepridil weakly slowed the former and markedly increased the latter. CERM 11888 caused a lengthening of RP but this was a delayed effect. 5. In the ventricle, bepridil and CERM 11888 caused a small increase in the QRS and a more pronounced increase in the RP. Both compounds increased QTc but did not modify HV. Verapamil and diltiazem had no significant effects at the ventricular level. 6. Our results confirm that the main sites of action of calcium antagonists are the SA and AV nodes. Bepridil has a broader spectrum of activity and also acts at the atrial and ventricular levels. A comparison of the effects of bepridil with those of its quaternary derivative suggests the involvement of an intracellular action in the electrophysiological effects of bepridil.

Comparative effects of bepridil, its quaternary derivative CERM 11888 and verapamil on caffeine-induced contracture in ferret hearts.

1. The effects of bepridil, its quaternary derivative: CERM 11888 (methyl-pyrrolidinium bromide) (10(-7)-10(-5) M), and verapamil (10(-7)-10(-6) M) were compared on caffeine-induced contracture of isolated ventricular trabeculae of the ferret. 2. Bepridil diminished the amplitude of contracture in a concentration-dependent fashion, and this effect was significantly different from that of CERM 11888 which, like verapamil, only reduced the amplitude at the highest concentration used. 3. Bepridil (10(-6) M) significantly shortened the time to peak tension and accelerated the relaxation phase of contracture. This latter effect was different from that of CERM 11888. Verapamil (10(-6) M) also tended to accelerate the relaxation phase. At 10(-5) M these actions of bepridil on the time to peak and relaxation tended to reverse. 4. At all concentrations bepridil and verapamil reduced the rate of repriming of contracture and this effect of bedpridil was significantly different from that of its quaternary derivative which only showed a significant effect at 10(-5) M. 5. These results demonstrate a clear intracellular effect of bepridil in the ferret heart. Verapamil and CERM 11888 had only weak intracellular effects even at high concentrations. 6. Analysis of the results suggests that the main sites of action of bepridil in this model are the sarcoplasmic reticulum and one or two calcium compartments in the sarcolemma.

[(Arylpiperazino-4-butyryl)-6 benzoxazolinones and reduction products: chemistry and pharmacodynamic study]. / (Arylpipérazino-4 butyrl)-6 benzoxazolinones et preduits de réduction: étude chimique et pharmacodynamique.

The synthesis of various 6-(4-arylpiperazino-butyryl)-3-methyl-benzoxazolinones and their reduction products, 6-(4-arylpiperazino-1-hydroxy-butyl)-3-methyl-benzoxazolinones and 6-(4-arylpiperazino-butyl)-3 methyl-benzoxzolinones, is described. These compounds were tested for psychotropic and analgesic activities.

Electrophysiological effects of the new cardioactive drug CERM 4205: a comparative study in an animal model and in man.

The cardiac electrophysiological effects of CERM 4205, a new cardioactive agent, were studied by means of intracardiac electrodes in man and in anaesthetized dogs. The results show that CERM 4205 is a cardioactive drug with a main inhibitory effect on slow-response structures (sinus and atrioventricular node) with an associated effect on fast-response structures (atrial, His-Purkinje and ventricular tissues). No qualitative differences were observed between the effects observed in man and dogs. In conclusion, the present study confirms that CERM 4205 is a compound with combined class IV and class I electrophysiological effects in dogs and man. The anaesthetized dog appears to be a satisfactory model for the evaluation of the electrophysiological effects of cardioactive drugs.

Comparative effects of bepridil, diltiazem, nifedipine and verapamil on haemodynamic parameters and myocardial oxygen consumption in anaesthetized dogs.

The haemodynamic effects of 4 calcium antagonists, bepridil (1.25 to 5 mg/kg i.v.), diltiazem (0.1 to 0.3 mg/kg i.v.), nifedipine (0.01 to 0.03 mg/kg i.v.) and verapamil (0.1 to 0.3 mg/kg i.v.) were compared in anaesthetized open-chest dogs. The following parameters were measured: sinusal coronary blood flow (SCBF), total coronary vascular resistance (TCVR), aortic blood pressure, heart rate, left dP/dt max, amplitude of right ventricular contraction, double product, myocardial oxygen consumption (MVO2) and arterial and coronary venous blood gases (pO2 and pCO2) and pH. All 4 substances increased SCBF and decreased TCVR. The greatest effects, taking into account relative dose size, were obtained with nifedipine and verapamil. These 2 substances also had the greatest effect on systemic vasodilatation, as reflected by hypotension. The 4 substances had a direct negative chronotropic effect on the myocardium, an effect which was masked by reflex sympathetic stimulation and decreased vagal tone secondary to a drop in blood pressure. The most marked negative chronotropic effects were seen with diltiazem, verapamil and bepridil in that order. Nifedipine and verapamil produced the greatest negative inotropic effects, whereas diltiazem had very little effect on this parameter. The direct consequence of these haemodynamic effects of the 4 substances was to improve oxygenation of the myocardium. The most durable effect on PvO2 was seen with nifedipine and verapamil. The findings demonstrate not only the heterogeneous action of the 4 calcium antagonists, but also the influence of the experimental conditions on the effects obtained with these substances.

Effect of methylated bepridil on slow action potentials in cardiac muscle and vascular smooth muscle.

The anti-anginal agent bepridil blocks slow Ca2+ channels in a variety of tissues. Since bepridil accumulates inside cells, the possibility exists that bepridil acts, at least partially, from inside the cell. To test this possibility, we examined the effects of a quaternary ammonium analog of bepridil, methylated bepridil, which presumably would enter the cells less readily, on the Ca2+-dependent slow action potentials of guinea pig papillary muscles (in 25 mM [K+]0) and rabbit pulmonary arteries (in tetraethylammonium chloride). In cardiac muscle, methylated bepridil had little effect on the slow action potentials at low stimulation frequencies (0.5 Hz), but at higher frequencies (1.0 and 2.0 Hz) the slow action potentials were depressed and/or the muscle was unable to follow each stimulation. These effects are similar to those obtained with bepridil, but bepridil was more potent than methylated bepridil. In vascular smooth muscle cells, methylated bepridil inhibited the slow action potentials at a somewhat lower dose than bepridil. We conclude that, in cardiac muscle, bepridil probably has two sites of action, one outside the cell (presumably on or associated with the slow Ca2+ channel) and a second site inside the cell. On the other hand, in vascular smooth muscle cells, bepridil may act only on an external site.

Effects of bepridil and of its quaternary derivative on rat tail artery.

The effects of bepridil and its quaternary ammonium derivative (BN+) were compared, showing that: (i) both drugs inhibited K+-induced contractions with similar time courses and potencies, (ii) bepridil blocked the tonic but not the phasic component of contractions elicited by noradrenaline, whereas BN+ had no effect on noradrenaline-elicited contractions. These results, and the relative insensitivity of skinned taenia caeci to bepridil, suggest that this drug and BN+ do not act directly on contractile proteins but affect K+- and noradrenaline-induced calcium channel activities differentially.

[Benzoxazolinone phenylethanolamine antagonists of adrenergic receptors. A chemical and pharmacodynamic study]. / Phényléthanolamines benzoxazolinoniques antagonistes des récepteurs adrénergiques. Etude chimique et pharmacodynamique.

Benzoxazolinone can be considered as a bioisosteric analogue of pyrocatechol. This concept has led to the synthesis of benzoxazolinonic phenylethanolamines. The pharmacological study shows that these compounds possess an affinity for adrenergic receptors. Compound (XXXIV), the most interesting, is a competitive alpha and beta adrenergic antagonist which has been studied for antihypertensive activity.

Effects of bepridil and nifedipine on regional myocardial contractility during ischaemia in anaesthetized dogs.

Subtotal reduction (60%-70%) of blood flow in the circumflex artery in anaesthetized open-chest dogs caused a long-lasting increase (222%) in coronary vascular resistance and stable changes in myocardial segmental contractility (% delta L), as measured by the method of piezoelectric crystals. % delta L increased by 31.2% in the healthy zone while hypokinesia occurred in the moderately ischaemic zone (-50.8%). In the severely ischaemic zone there was a paradoxical lengthening (bulge or dyskinesia) of 7.3% during systole. Bepridil (2.5 mg.kg-1, IV) decreased heart rate (-15.6%) and systolic (-20.8%) and diastolic (-31.6%) blood pressure, and increased total coronary blood flow (+40.7%). % delta L was increased in the healthy zone (+20.4%) and in the moderately ischaemic zone (+48.2%). Bepridil completely inhibited the bulge in the severely ischaemic zone. Nifedipine (0.02 mg.kg-1, IV) greatly reduced systolic (-31.3%) and diastolic (-40.7%) blood pressure as well as coronary blood flow (-30.4%), without changing heart rate. A delayed increase in % delta L occurred in the healthy zone (+8.4%) and in the moderately ischaemic zone (+38.5%). In the severely ischaemic zone, there was no improvement of the bulge. The observed differences in contractility between the two calcium antagonists are discussed in terms of their haemodynamic differences. Improvement of myocardial segmental contractility, if it occurred, may have been due to bradycardia, slight decrease in contractility, as measured by LV dP/dt max/P, increased total coronary blood flow, decreased afterload, so long as it was not too great, and anti-ischaemic properties of the compound.

[Synthesis and pharmacologic study of 6-(amino-2 ethyl) benzoxazolinones]. / Synthèse et étude pharmacologique d'(amino-2 éthyl)-6 benzoxazolinones.

Reaction of various amines on 6-(2-bromoethyl)benzoxazolinone or its N-methylated derivative provided eleven new 6-substituted aminoalkyl analogues. In a pharmacological evaluation, several compounds bearing an arylpiperazinic moiety were found to possess significant effects on arterial blood pressure and on the central nervous system; two of them showed interesting analgesic activity.

Sudden death and experimental acute myocardial infarction.

Acute myocardial ischemia was produced by ligature of the anterior descending coronary artery on 658 dogs in 3 separate laboratories. Overall, 12% of the dogs died within the first hour (instantaneous death) and 25% within the first 24 hours (sudden death). The sudden death rate was significantly related to the logarithm of the weight of the dogs in the range studied. It varied widely if values from small series, comprising the same number of dogs, were considered. Values became less dispersed as the size of the series increased. In series of 10 dogs, sudden death rates ranged from 0 to 70%, whereas in series of 100 dogs the range was 14 to 36%. Stable values were obtained for 50 to 60 dogs per series. Accordingly, reliable assessment of preventive measures can be made only with experimental series of at least this size.

Cardiotoxicity of high doses of isoproterenol on cardiac haemodynamics and metabolism in SHR and WKY rats.

The haemodynamic and metabolic effects on the heart due to high doses of isoproterenol were compared in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. In baseline conditions, the hypertrophied SHR heart displayed perfectly constant haemodynamics but had fewer energy reserves than the WKY heart. Isoproterenol (2 X 25 mg/kg, s.c.) caused high mortality, myocardial ischaemia, and heart failure in the SHR. These effects were accompanied by anaerobic metabolism. In the WKY rats, on the other hand, isoproterenol caused no changes in ST-segment elevation and no cardiac insufficiency; in addition, aerobic metabolism was maintained. A marked drop in coronary perfusion pressure and excessive accumulation of calcium in the myocardium account, in part, for the effects seen in the SHR. The results indicate that isoproterenol-induced heart failure in the SHR might be a useful model for selecting compounds designed to treat this disease.

Bepridil-induced modifications of cardiac performance in the anesthetized dog: comparison with nitroglycerin and propranolol.

Bepridil, a new anti-anginal drug, increases coronary blood flow and reduces myocardial oxygen consumption. The comparative effects of bepridil (2.5 mg.kg-1), nitroglycerin (40 microgram/.kg-1) and propranolol (0.5 mg.kg-1) on myocardial performance, were studied in anesthetized dogs. All drugs were injected intravenously within 60 sec. Continuous recordings of left ventricular end-diastolic pressure, peripheral arterial pressure and external ventricular dimensions were made during a 31 min period following drug administration. Similarly, several contractility indices were calculated during the phase of isovolumic contraction. Bepridil was found to decrease left ventricular work, by 14.3 +/- 4.4% while increasing aortic blood flow by 24 +/- 6%. In addition, this compound weakly and only briefly decreased contractility, but reduced the afterload more markedly by 34.2 +/- 3.8%. The external ventricular circumference was only slightly increased. Nitroglycerin reduced aortic flow, ventricular dimensions together with the pre- and afterloads. Propranolol reduced aortic flow while considerably increasing ventricular dimensions and preload. Thus, in the anesthetized dog, the intravenous administration of bepridil decreases left ventricular work while increasing aortic blood flow. Both effects occur during mild and prolonged bradycardia.

Studies on the bradycardia induced by bepridil.

Bepridil, a novel active compound for prophylactic treatment of anginal attacks, induced persistent bradycardia and a non-specific anti-tachycardial effect, the mechanisms of which were investigated in vitro and in vivo. In vitro perfusion of bepridil in the life-support medium for isolated sino-atrial tissue from rabbit heart, caused a reduction in action potential (AP) spike frequency (recorded by KCl microelectrodes) starting at doses of 5 X 10(-6) M. This effect was dose-dependent up to concentrations of 5 X 10(-5) M, whereupon blockade of sinus activity set in. Bepridil at a dose of 5 X 10(-6) M, induced a concomitant reduction in AP amplitude (falling from 71 +/- 8 mV to 47 +/- 6 mV), maximum systolic depolarization velocity (phase 0) which fell from 1.85 +/- 0.35 V/s to 0.84 +/- 0.28 V/s, together with maximum diastolic depolarization velocity (phase 4) which fell from 38 +/- 3 mV/s to 24 +/- 5 mV/s. In vivo injection of bepridil at a dose of 5 mg/kg (i.v.) into 6 anaesthetized dogs which had undergone ablation of all the extrinsic cardiac afferent nerve supply, together with a bilateral medullo-adrenalectomy, caused a marked reduction in heart rate which fell from 98.7 +/- 4.2 beats/min to 76 +/- 5.3 beats/min sustained for more than 45 min. It is concluded that bepridil reduces heart rate by acting directly on the sinus node. This effect, which results in a flattening of the phase 0 and phase 4 slope, together with a longer AP duration, may be due to an increase in the time constants of slow inward ionic currents (already demonstrated elsewhere), but also to an increased time constant for deactivation of the outward potassium current (Ip).

2-Benzodioxinylaminoethanols: a new class of beta-adrenergic blocking and antihypertensive agents.

Various 2-benzodioxinylaminoethanol derivatives were synthetized and investigated for beta-adrenergic blocking activity. Most compounds demonstrated a beta-blocking activity of a competitive type when evaluated in guinea pig atrial and tracheal preparations. Three compounds were more potent than practolol and propranolol. All compounds demonstrated antihypertensive properties in spontaneously hypertensive rats. The most active compound was 1-(1,4-benzodioxin-2-yl)-2-[N4-(2-methoxyphenyl)piperazino]ethanol (11), which at 2.5 mg/kg iv lowered blood pressure by 41%.

Regional cerebral and extracranial blood flow measurements in acutely and chronically implanted cats: hydrogen clearance technique.

A technique is described for measuring regional blood flow concomitantly in the brain and in extracranial tissues of the cat. Hydrogen clearance using the tissue polarographic electrode appears to be a useful technique for intermittent measurements of cerebral blood flow (CBF) in relatively small areas. H2 was administered by inhalation for 10 min. Both chronic and acutely implanted electrodes were placed at different depths in the cat brain, on the surface of the cortex, and in extracranial tissues. Clearance rates in gray matter of 75 to 119 ml/min/100 g tissue have been obtained and of 11 to 14 ml/min/100 g tissue in white matter. Clearance curves have invariably been monoexponential in character in white matter and biexponential in gray matter. Successful recordings of H2 clearance curves were obtained from both chronically (up to 5 months) and acutely implanted electrodes. A new type of electrode is described. The "paperclip" electrode is placed at the surface of the cortex, has a reactive surface much greater than that of needle electrodes, thus limiting the possible variations due to vascularization differences from one local area to the next, and induces no damage to the brain tissue. To test the reliability of the technique, blood flow was measured during hypercapnia and progressive exsanguination. All electrodes indicated increased rCBF following 5-7% CO2 inhalation. A marked decrease in blood flow was seen with peripheral electrodes during exsanguination, whereas it was necessary to lower arterial blood pressure by more than 60% of the baseline value to record decreased flow in brain tissues. The constancy of response from electrodes and the lack of obvious tissue damage on dissection of the brain renders the method an adequate one. It provides highly focal recording of both CBF and extracranial flow in chronically implanted animals.

5-Hydroxytryptamine receptors. Contractile activity and mode of inhibition by methysergide in mammalian intracranial and extracranial vessels.

The contractile effect of 5-HT on intra- and extracranial arteries from rabbit, cat, dog and man and its interaction with methysergide was investigated. ED50 and EAm values for 5-HT from both types of arteries differed. Intracranial arteries stimulated by 5-HT were more sensitive to methysergide than extracranial arteries. In intracranial vessels the methysergide antagonism is non-competitive while in extracranial it is competitive. These differences might suggest a heterogeneity of 5-HT receptors located within the cranial circulation.

Comparison of the cardiovascular actions of ORG NC 45 with those produced by other non-depolarizing neuromuscular blocking agents in experimental animals.

The cardiovascular actions of 1- [(2 beta,3 alpha, 16 beta,17 beta)-3,17-bis(acetyloxy)-2-(1-piperidinyl)-androstan-16-yl]-1-methyl-piperidinium bromide (Org NC 45) are reviewed and compared with those of other non-depolarizing neuromuscular blocking drugs. Results obtained in anaesthetized cats and dogs have demonstrated that, in contrast to other neuromuscular blocking drugs, Org NC 45, even in doses 20 times greater than those required for neuromuscular block, has no effects on heart rate, arterial pressure, autonomic ganglia, adrenoceptors or baroreceptors activity. Studies in pithed rats and on guineapig atria have further shown that Org NC 45 has little effect on cardiac muscarinic receptors or on noradrenaline re-uptake mechanisms. These results suggest that Org NC 45 possesses significant advantages over presently used non-depolarizing neuromuscular blocking drugs, since its clinical use should not be associated with cardiovascular side-effects.

Interaction of a potential antimigraine drug (Org GC 94) with the vasomotor action of serotonin.

The interaction of a potential anti-migraine drug (Org GC 94) with the vasomotor action of 5-HT in vitro in feline, canine and human intra- and extracranial arteries, as well as in vivo in the canine nasal vascular bed as been investigated. In the two in vitro preparations, i.e. using superfusion or bath techniques, the intracranial vessels were more sensitive to 5-HT vasoconstriction than the extracranial ones. As both the maximum contraction and the slope of the dose-response curves were reduced by increasing concentrations of Org GC 94, the antagonism of 5-HT did not involve competitive blockade of 5-HT receptors. The dilator response was tested in arteries brought to a higher tone with prostaglandin F2 alpha. 5-HT produced a dose-dependent dilatation which, like the vasoconstriction, was antagonized in a non-competitive manner by Org GC 94. Intra-arterial injections of 5-HT provoked nasal vasoconstriction and this response was clearly potentiated by Org GC 94 in low doses while higher doses inhibited the vascular response to 5-HT. The specific effect of Org GC 94 in vivo may be the potentiation of 5-HT-induced vasoconstriction. The hypothesis is discussed that the so-called anti-5-HT agents act in migraine patients as partial agonists of 5-HT, mimicking rather than antagonizing 5-HT.

An automated superfusion technique for measuring circular muscle contraction. Effects of serotonin on intra- and extracranial arteries.

A new in vitro technique is described and its advantages are demonstrated: "true" circular contraction is measured; arteries are in cascade, permitting comparison of intra- and extracranial arteries from the same animal; the mechanical influences on contractility are reduced; long-lasting experiments of up to 50 h can be performed; the procedure is fully automated. The maximal effect of an agonist was not only markedly modified during the first 2--4 h after fixing the arteries in the apparatus but also slightly during the next 3--4 h. After the initial stabilization period, the arterial response to an agonist remained highly reproducible for 24--48 h (standard deviation not exceeding 7%). This was demonstrated in all the types of arteries tested. With serotonin as agonist, there was a significant difference in --log ED50 values for intracranial arteries (basilar 8.70, middle cerebral 8.72) vs. extracranial (lateral nasal 8.15; facial 8.14) and peripheral (branch of saphenous 8.14) arteries.