Effects of bencyclane on normal and cevadine-modified Na channels in frog skeletal muscle.

The effect of 10(-5) mol/l bencyclane on the repetitive electrical activity of muscle membrane was studied with the conventional microelectrode technique. Electrical activity was induced by repetitive stimulation in normal Ringer solution (train) or by a single depolarizing current pulse in the presence of 10(-6) mol/l cevadine (volley). Bencyclane decreased, in a use-dependent manner, the maximum rates of depolarization and repolarization (Vmax+ and Vmax-, resp.) of the action potentials both of the train and the volley. The inhibition of Vmax+ and Vmax- was proportional; however, it was stronger for the volleys than for the trains. The cycle length (mean interspike interval) of the volley was increased by bencyclane; the prolongation was progressive during consecutive cycles. The dissociation of bencyclane from the Na channel was studied by applying trains of different durations with equal pulse numbers. Bencyclane at a higher concentration (5 x 10(-5) mol/l) caused a reversible tonic block: the overshoot potentials, Vmax+ and Vmax- were markedly reduced. The reduction of Vmax- was slightly stronger than that of Vmax+. Slow membrane potential oscillation (SMPO) was evoked by treating the muscle with 10(-4) mol/l of cevadine. The administration of 5 x 10(-6) mol/l bencyclane decreased the frequency of SMPO, while 10(-5) mol/l bencyclane terminated the slow oscillation activity without changing its baseline potential. The present results indicate that bencyclane induces use-dependent inhibition of Na channels in muscle, similarly as do class 1 antiarrhytnmic drugs. Inhibition was observed with both normal and cevadine-modified Na channels.

Slow channel inhibitor effects on brain function: tolerance to severe hypoxia in the rat.

1. The protective effects of ten slow channel inhibitor drugs against severe progressive hypoxia were investigated in rats breathing spontaneously during light anaesthesia. Respiration, heart rate, electrocorticogram (ECoG) and/or electroencephalogram (EEG) were recorded. 2. Tolerance times were monitored from hypoxia onset until cessation of respiration, ECoG, EEG synchronization, and 'background-EEG'. Drugs were administered i.v. 5 min before the onset of hypoxia. 3. Verapamil, gallopamil, and nimodipine resulted in a significant increase of tolerance times; fendiline and bepridil showed a small increase (not significant); bencyclan and prenylamine were ineffective; cinnarizine and diltiazem slightly reduced tolerance times as did flunarizine at low doses. 4. At protective doses, verapamil, gallopamil, and nimodipine significantly raised the respiration rate but had little or no cardiac depressor effects. Bencyclan showed ventilatory drive but cardiocirculatory depression. A clear-cut ventilatory drive did not occur with the other ineffective slow channel inhibitors. 5. It is suggested that the protective actions observed were not due to slow channel inhibition per se, nor to spasmolytic potency or increased cerebral blood flow. Ventilatory drive associated with other cardiopulmonary actions which secondarily raise the brain oxygen supply are likely to be responsible for this effect.

Use-dependent blockade of sodium channels induced by bencyclane in frog skeletal muscle and canine cardiac Purkinje fiber.

Applying conventional microelectrode technique, the effect of bencyclane was studied on the maximal rate of rise (Vmax) of the transmembrane action potential in frog skeletal muscle and canine cardiac Purkinje fiber. Bencyclane (10 microM) decreased the Vmax from 333.7 +/- 6.9 V/sec to 302.7 +/- 10.2 V/sec (n = 6, p less than 0.05) in skeletal muscle without changing the resting membrane potential. If repetitive stimulation with different constant cycle lengths was applied, a further, frequency-dependent decrease of Vmax developed in both tissues with similar frequency-dependence. In skeletal muscle bencyclane increased the time of 50% repolarization by 33.3 +/- 2.5% (n = 7, p less than 0.01) and decreased the overshoot potential by 11.3 +/- 0.72 mV (n = 7, p less than 0.01) measured at 250 msec cycle length. In cardiac Purkinje fiber bencyclane shortened the action potential duration (APD90) from 258.3 +/- 15.4 msec to 241.7 +/- 12.1 msec (n = 6, p less than 0.05) without changing the resting membrane potential and action potential amplitude measured at 500 msec cycle length. The comparable size of the Vmax-block at the same cycle lengths observed in skeletal muscle (short APD) and Purkinje fiber (long APD) suggests that the inhibition may by mainly attributed to the open sodium channel population. It was concluded that the antiarrhythmic action of bencyclane, based on the use-dependent blockade of sodium channels, might be an important component of the therapeutic effect of bencyclane.

Effects of cerebro-protective agents on enzyme activities of rat primary glial cultures and rat cerebral cortex.

The effects of different cerebro-protective agents on selected key enzymes of the energy metabolism of rat primary glial cultures and rat cerebral cortex were studied. As indicators for the capacity of the most important pathways of energy metabolism the following enzyme activities were determined: hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G-6-P-DH), malate dehydrogenase (MDH), glutamate dehydrogenase (GDH), and cytochrome-c-reductase (CCR). After a one week growth period, rat glial cultures were incubated for 3 or 4 weeks with the substances to be tested. Bencyclane (5 X 10(-5) mol/l) increased the activities of HK, G-6-P-DH, and LDH, whereas PFK and CCR were reduced. Pyritinol (10(-4) mol/l) led to a higher G-6-P-DH activity, simultaneously lowering the values for PFK, CCR, PK, LDH, and MDH. Under the influence of an extract of the leaves of Ginkgo bilobae (EGB; 100 mg/l) PFK, LDH, and MDH activities were reduced. All these alterations in enzyme activities went along with simultaneous reductions in protein content, therefore not allowing to exclude toxic effects with regard to the doses used. Moreover, direct interference with the analytical procedure was demonstrable for bencyclane and EGB. Piracetam (10(-3) mol/l), flunarizine (10(-6) mol/l), dihydroergocristine (5 X 10(-6) mol/l), and nicergoline (5 X 10(-6) mol/l) failed to induce any alteration in the employed doses. The most striking effects were obtained with meclofenoxate which was tested at 10(-3) and 10(-4) mol/l. The higher dose caused an elevation of HK, PFK, CCR, G-6-P-DH, GDH and MDH activities, while slightly reducing PK. With the lower dose of meclofenoxate CCR and G-6-P-DH activities were increased. Short-term incubation of the cultures with 10(-3) mol/l meclofenoxate for 24 hr led to an increase in LDH, G-6-P-DH, and GDH activities. Chronic incubation with meclofenoxate (10(-3) mol/l) followed by 48 hr deprivation of the drug resulted in elevated HK, PFK, CCR, G-6-P-DH, GDH, and MDH activities. These changes were accompanied by alterations in related metabolite levels. These include elevations in the concentration of creatine phosphate and fructose-1,6-bisphosphate, whereas glucose-6-phosphate levels were reduced. After one week of meclofenoxate deprivation the activities of CCR and G-6-P-DH were still elevated. The metabolites of meclofenoxate dimethylaminoethanol (DMAE; 10(-3) mol/l) and p-chlorophenoxyacetic acid (10(-3) mol/l) were also investigated.(ABSTRACT TRUNCATED AT 400 WORDS)

Tracheal phenol red secretion, a new method for screening mucosecretolytic compounds.

A simple method for screening drugs that influence tracheobronchial secretion has been described. After i.p. application of a phenol red solution, part of the dye is secreted into the tracheal lumen. This basal secretion is increased by both parasympathomimetics and sympathomimetics. In addition, expectorants are also capable of increasing tracheal phenol red output. Therefore this method is suitable for the study of drugs that may be capable of influencing tracheobronchial secretion.

[Modification of metastasis formation by inhibition of platelet aggregation. Experimental and clinical results]. / Beeinflussung der Metastasierung durch Hemmung der Thrombozytenaggregation. Experimentelle und klinische Ergebnisse.

Our clinical study to prevent relapse and metastases in several sarcomas and malignant lymphomas of the head and neck region with a long-term treatment with mopidamole was initiated in 1972 because the pyrimido-pyrimidine derivative was shown to inhibit platelet aggregation in vivo and to increase significantly the circulation time of intravenously injected, 32P-labelled Ehrlich ascites tumour cells in mouse blood. The aggregation of platelets to circulating tumour cells and their subsequent adhesion to vascular endothelium in turn appeared to be part of the early stages of the metastatic process. It seems, however, that other related mechanisms are also involved in the clinical results obtained. Mopidamole, as other related derivatives, probably inhibits platelet aggregation by inhibition of PDE-induced decomposition of cAMP and may stimulate the synthesis and/or release of prostacyclin from the vessel wall which in turn activates adenylate cyclase involved in cAMP synthesis. The latter mechanism was definitely shown only for the related pyrimido-pyrimidine derivative dipyridamole, the methyl-xanthine derivative pentoxifylline and the methyl-pyrazoline derivative nafazatrom. The increase of cAMP levels by mopidamole results in an inhibition of 3H-thymidine incorporation into human neoplastic cells and a direct inhibition of its mitotic rate. The adding of mopidamole to a culture of a human promyelocytic leukemic cell line promotes a reverse transformation of the malignant cells to normal which appears to be a permanent phenotypic change. Furthermore, mopidamole was shown to diminish significantly spontaneous lung metastases in syngenic Wilms' tumor (nephroblastoma) of the rat, the C1300-neuroblastoma of the mouse and the HM-Kim mammary carcinoma of the rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurogenic component in the effect of papaverine, drotaverine and bencyclane.

Papaverine, drotaverine and bencyclane, drugs considered to have direct action on the smooth muscle, inhibited synaptic transmission in the isolated a sympathetic ganglion of the frog. Their effect depended upon the concentration applied. The ganglionic blocking effect of papaverine and drotaverine in the concentration range from 10(-8) to 10(-6) mol/l was partially antagonized by naloxone and nalorphine as well as by increasing the Ca2+ concentration in the incubation medium. This refers to an activation of specific opiate receptors in the mechanism of ganglionic action of these drugs. The ganglionic effect of bencyclane may be due to its local anaesthetic property, since it was prevented by neither naloxone nor nalorphine, and an increase in the Ca2+ concentration in the medium had no influence on it.

Comparative studies of cerebral vasodilators on relaxation activities in isolated basilar, mesenteric and pulmonary arteries of rabbits.

Effects of cerebral vasodilators such as bencyclane, cinnarizine, and papaverine were comparatively studied using helically cut basilar and superior mesenteric arteries and radial muscle preparations of pulmonary arteries with the sympathetic nerve isolated from rabbits. The order of relaxation activities on high K+-induced contractures was cinnarizine>bencyclane>papaverine in basilar strips and cinnarizine>papaverine>bencyclane in mesenteric strips. Relaxation responses of basilar strips to cinnarizine and bencyclane were faster and more marked than those seen in mesenteric strips. Responses to papaverine were equipotent in both preparations. The action of cinnarizine alone was irreversible. In mesenteric strips, the order of the sensitivity of contractile responses to cumulatively applied biogenic amines was serotonin>noradrenaline>histamine. Cinnarizine produced an antihistaminergic action, while bencyclane produced an antiserotonergic action. In pulmonary arteries, 6 x 10(-6) g/ml papaverine inhibited contractile responses to 2, 5, and 25 Hz nerve stimulation in a frequency-independent manner together with inhibition of responses to noradrenaline. Bencyclane at 6 x 10(-6) and 10(-5) g/ml selectively inhibited in a dose-dependent manner contractile responses only to 25 Hz without inhibition of responses to noradrenaline. These results were discussed in comparison with findings of the cerebral vasodilators obtained using other experimental techniques. Spiral strips of basilar arteries from rabbits in combination with peripheral arteries may be used as a simple quantitative, and reproducible screening method in a preclinical stage for drug evaluation of cerebral vasodilators.

Pial arteriolar reaction to intravenous administration of bencyclane in the cat.

In a series of 29 experiments in cats, the vasodilatory effect of Bencyclane on pial arterioles was investigated by means of the cranial window technique, using an image-splitting eyepiece, a photometric method or simple microscopic observation. Intravenous injection of 3 mg kg-1 led to vasodilatation in all experiments, yet decreased blood pressure within 30--40 sec until 5--6 min down to 70% of resting pressure. Mean maximal dilatation of arterioles with a 76-micrometers mean resting diameter was 53%. After normalization of blood pressure, arteriolar diameters remained increased by 5--10% for further 10 min, thus indicating increased cerebral blood flow for a total time of about 15 min. During intravenous infusion of 0.2--0.3 mg kg-1min-1 of the drug, pial arterioles dilated by about 10% with blood pressure remaining on resting levels. A higher dosage rate of infusion evoked further vasodilatation, yet parallel decrease of blood pressure.

[Effect of bencyclan and theophylline on changes of platelet aggregation and factor 3 activity]. / Die Veränderungen der Thrombozytenaggregation und Faktor-3-Aktivität unter der Wirkung von Bencyclan und Theophyllin.

The ADP- and adrenaline-induced platelet aggregation and platelet factor 3 availability were studied in patients before and eight hours after intravenous administration of bencyclan (100 mg) and/or theophylline (240 mg). Aggregation was primarily inhibited by bencyclan, the availability of factor 3 was inhibited by theophylline. Combination of both drugs exerted additive effects on both parameters. The combined use of drugs as inhibitors of aggregation is recommended, since they inhibit primary haemostasis simultaneously at two points of attack.

Effect of mepacrine on gastric motility in the rat.

Mepacrine given orally to rats inhibits gastric motility; its blocking effect is comparable to that of chloroquine, papaverine, and drotaverine, but less expressed than that of bencyclane. Similarly as the delayed gastric emptying induced by chloroquine, the effect of mepacrine is antagonized by acetyl-beta-methylcholine in a dose-related fashion, while that of papaverine, drotaverine, and bencyclane remains unchanged after treatment with the cholinomimetic drug.

[Cardiac output and central-hemodynamic parameter under bencyclan (author's transl)]. / Herzminutenvolumen und zentralhämodynamische Parameter unter Bencyclan (Fludilat).

In 17 patients with peripheral arterial occlusive disease the influence of intra-veinously applicated Bencyclane (Fludilat) on cardiac output and central-hemodynamic parameter has been investigated. While 100 mg (n = 8) of Bencyclane almost do not influence cardiac output, 200 mg (n = 9) cause a significant decrease of minute-volume of the heart by-17.22% and of heartfrequency by-8.85%. With either dose there is also a significant increase of aortic pressure, pulmonary arterial pressure and pulmonary vessel resistance to be seen. These results correlate with the animal-experimental proof of a negative inotropy under Bencyclane, and they have to be considered in therapeutical use.

[Primary shape change of platelets in vitro (author's transl)]. / Primärer Formwandel der Thrombozyten in vitro.

Studies with interference contrast microscopy reveal that platelets undergo a typical shape change within 30--60' after venepuncture, i.e. swelling, formation of large tentacles, tiny protrusions and vesicles at the platelet surface. This "shape change" can be observed in citrated blood and PRP, heparinized blood and EDTA-blood as well. It is enhanced by low incubation temperatures (4 degrees C, 10 degrees C) and delayed at 37 degrees C as compared with room temperature. An increased number of primarily shape changed platelets is found if platelets are strongly mechanically irritated at blood sampling. The shape change is partly reversible in vitro, it is completely or almost completely reversible in vivo. Some antiaggregating agents inhibit the in vitro shape change at varying degrees (Bencyclan, SH 869 greater than ASA greater than D-Propranolol). The shape change is partly inhibited after oral or i.v. administration of ASA. A typical transformation of platelets into "spheric" forms can be observed following the addition of Bencyclan, SH 869 and D-Propranolol to PRP in vitro. The spontaneous "primary shape change" which occurs in PRP or blood after blood sampling is probably different from the secondary ADP-induced shape change. The primary shape change may influence the results of different platelet function and aggregating tests. The shape change kinetics of "healthy" subjects and patients with Hodgkin's disease differ significantly. The described method may gain more clinical interest in the future.