The activity of reserpine and a possible mechanism by which it reverses the resistance to both doxorubicin and pirarubicin in doxorubicin-resistant P388 leukemia (P388/DOX) cells were examined in vitro. During 48 hr drug-exposure, the sensitivity of doxorubicin and pirarubicin were potentiated markedly when reserpine was present at the concentration of 1 μg/ml, which is not toxic to P388 leukemia (P388/S) cells. However, reserpine had little effect on the cytotoxicity of doxorubicin and pirarubicin in the sensitive parent cell. Reserpine at 0.5 ?? 20 μg/mi increased intracellular accumulation of doxorubicin and pirarubicin in the drug-resistant cells. The potentiating action of reserpine was stronger when the cells were preincubated with reserpine within 30 min. Efflux of doxorubicin and pirarubicin was greater in drug-resistant cells compared to sensitive cells. This enhanced efflux of drug resulted in a decrease in the intracellular accumulation of doxorubicin in the drug-resistant cells. When the resistant cells were exposed to 2 μg/ml of reserpine, this enhanced efflux was blocked. A similar effect of reserpine on doxorubicin was seen with the efflux pattern of pirarubicin. From the measurements of drug uptake and efflux, it seems that like other multiple drug resistance modifiers, reserpine modulates anthracycline resistance by increasing intracellular accumulation of drug.

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The bronchodilating effect and other related pharmacological properties of SN-408 were studied in comparison with those of isoproterenol, salbutamol and procaterol. SN-408 caused concentration-dependent relaxation of isolated guinea pig trachea via the β₂-adrenoceptor. The order of relaxation potency was: procaterol > SN-408 ≥ isoproterenol > salbutamol, but the duration of the action of SN-408 was far longer than those of other β-agonists. Positive chronotropic and inotropic actions of SN 408 in isolated guinea pig right atria and left atria were less potent than those of other β-agonists. In isolated guinea pig lung tissues, SN-408 increased cyclic AMP contents. Also in vivo, SN-408 showed dose-dependent bronchodilating action by i.v. administration in anesthetized guinea pigs and by inhalation in conscious guinea pigs. Bronchodilating actions of SN-408 were less potent than those of procaterol and isoproterenol, but the duration of action of SN-408 was far longer than those of other β-agonists. SN-408 showed no evidence of the development of tolerance to the bronchodilating action. SN 408 caused small tachycardia in guinea pigs by i.v. and inhalation. SN-408 given i.v. suppressed vascular permeability in mice. These results indicate that SN-408 is a long-acting and selective β₂-stimulant bronchodilator.

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Bilateral occlusion of the carotid arteries (BCAO) killed 52% of the male ddY mice (N=86) and 77% of the ICR mice (N=96) within 10 min, and the mean survival time of the ddY strain recorded for the 10 min was significantly longer than the time of the ICR strain. Among animals that survived longer than 1 hr after BCAO, some (5 of ddY and 3 of ICR) were able to survive for more than 24 hr. All of the neurobehavioral and histopathological signs developed by BCAO and in most cases followed by death were found to be also inducible by unilateral occlusion alone, although this was in a small fraction of mice. The brain levels of ATP, glucose and acetylcholine significantly decreased in mice that died within 10 min after BCAO, while none of these changes were detectable in mice surviving BCAO for 1 hr, just as in mice that died by carbon monoxide or ether inhalation. The results obtained herein indicate that mice may not be homogeneous in the functional level of the collateral route of blood supply to the brain tissue and/or in the sensitivity toward the ischemia-inducible lethality.

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The ripening effect of dehydroepiandrosterone sulfate (DHA-S) on the uterine cervix was studied after intravaginal application. A 100-mg suppository containing 0, 5, 10 or 20% (w/w) DHA-S was applied to the vagina of pregnant rats 3 times on days 14-16 of gestation. Wet weight and water content of the uterine cervix increased dose-dependently. To measure the elasticity of the uterine cervix, the tension causing an expansion of 1 mm or 2 mm was determined; this was reduced by the application of 20% DHA-S, and the difference in the length of the cervix produced by tensions of 5 g and 25 g was increased. Application of 20% DHA-S decreased the collagen content of the uterine cervix and the total collagenase activity was increased. Furthermore, histochemical changes, coarsening and edema were observed in the uterine cervix. These findings suggest that intravaginal application of DHA-S would produce ripening effects similar to those after intravenous injection.

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The behavioral and EEG effects of the 5-HT_1A partial agonist ipsapirone were investigated to determine its pharmacological characteristics as an anxiolytic drug in rats, mice and rabbits, as compared with those of buspirone and diazepam. 1) The anticonflict effect of ipsapirone was almost equipotent as that of buspirone and less potent than that of diazepam in rats. Rol5-1788 antagonized the anticonflict effect of diazepam, but did not that of ipsapirone. 2) Muricide in midbrain raphe-lesioned and olfactory bulbectomized rats was inhibited by ipsapirone. However, the inhibition of muricide by ipsapirone was attenuated by its repeated administration. 3) The muscle relaxant effects of ipsapirone and buspirone on rotarod performance were less potent than that of diazepam. Ethanol-induced muscle relaxation was markedly potentiated by diazepam, but less potently by ipsapirone and buspirone. 4) The pentetrazolinduced convulsion was dose-dependently antagonized by diazepam, while it was weakly potentiated by ipsapirone and buspirone. 5) The limbic afterdischarges induced by either hippocampal or amygdaloid stimulation in rabbits were markedly inhibited by diazepam. Conversely, ipsapirone and buspirone slightly potentiated afterdischarges. In conclusion, it is suggested that ipsapirone has anxiolytic activities similar to that of buspirone and moderate antimuricidal action. In addition, ipsapirone, like buspirone, is also characterized by its less potent muscle relaxant, alcohol-potentiating and anticonvulsant actions.

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Effects of low molecular weight heparin (FR-860) on experimental disseminated intravascular coagulation (DIC) models in rats were compared with those of conventional unfractionated heparin (UFheparin) and other anticoagulants. In the endotoxin-induced DIC model, FR-860 (12.5 ?? 200 U/kg/hr) and UF-heparin (25 ?? 200U/kg/hr) inhibited dose-dependently the decreases in platelet counts, fibrinogen, antithrombin III activity and a2-plasmin inhibitor activity, and they also inhibited the increases in fibrin deproducts and thrombus formation in the glomerular capillary bed. Neither gabexate mesilate (FOY, 10 mg/kg/hr) nor nafamostat mesilate (FUT, 0.1 mg/kg/hr) improved endotoxininduced DIC. FR-860 showed comparable potency to UF-heparin in plasma anti-factor Xa (F.Xa) activity. However, FR-860 was weaker than UF-heparin in prolongation of activated partial thromboplastin time. In the thrombin-induced DIC model, both FR-860 and UF-heparin significantly improved, as seen in the endotoxin-induced DIC model, the changes in coagulation and fibrinolytic parameters and suppressed the production of pulmonary thrombus. On the other hand, both FOY and FUT showed significant but weak improvement in this model. In addition, FR-860 inhibited the enhancement of fibrinolysis and the production of pulmonary thrombus in the lactic acid-induced DIC model. These results suggest that the efficacy of FR-860 on DIC in rats is comparable to that of UF-heparin and that the efficacy can be attributed to its anti-F.Xa activity. FR-860 can be expected to be a useful therapeutic drug for DIC.

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