- Email: [email protected]
Prevention of ouabain-induced arrhythmia by a new beta blocker, PS-6 in isolated rabbit atria
80 PREVENTION OF OUABAIN-INDUCED ARRHYTHMIA BY A NEW BETA BLOCKER, PS-6 IN ISOLATED RABBIT ATRIA. A. Pousti, P. Somani and G. Shtacher* Tehran Univ. Sch. of Med., Tehran, Iran and Univ. of Miami Sch. of Med., Miami, U.S.A. We have recentl,v reported that erythro-dl-1-phenoxy-3-(3,4-dimethoxyphenethyl)-amino butan-2-ol (PS-6) has cardioselective effects in cats and blocks the effect of isooroterenol (I) on the rate and contractile force of isolated rabbit atria. The concentration of PS-6 needed to block the chronotropic response to I was 50 times that required to block the inotropic effect of I, suggesting that the adrenergic receptors for the inotropic response can be dissociated from those mediating the chronotropic response. To investigate the effect of PS-6 on the response of the heart to ouabain, in vitro experiments were carried out on the isolated rabbit atria. PS-6 (5X10e5M) decreased the rate and force of contractions of spontaneously beating right atria and electrically driven left atria (P(O.01). The drug also delayed significantly (P(D.01) the onset of arrhythmia and cardiac arrest induced by ouabain (1X10s6g).In presence of PS-6, ouabain increased significantly the contractile force of both atria but could not augment the rate of spontaneously beating right atria. The data suggest that PS-6 protects the heart against ouabain-induced arrhythmia and arrest, without preventing the positive inotropic effect of ouabain. (Supported by Fulbripht-Hays Visiting Professorship and US-Israel Binational Science Foundation. GS, present address Tel Aviv Univ. Sch, of Med.)
CARDIOVASCULAR EFFECTS OF VITEXIN. M C. Prabhakar, H. Bano, I. Kumar, M.A. Shamsi and M.S.Y. Khan. Research Division, Institute of History of Medicine and Medical Research, P.O. Madangir, New Delhi-110062, India. Vitexin (VT), 8-C-B-D-Glucopyranosyl-apigenin, isolated from Ochrowas investigated for its carpus longifolius and Arnebia hispidissima, VT (0.01 - 1.0 mg/kg, i.v.) elicited dosecardiovascular actions. independent rise in mean arterial pressure (m.a.p.1 of anaesthetized normotensive rats. In bilaterally adrenalectomized rats, however, a dosedependent fall was observed. With higher doses (1 mg/kg), after a latent bradycardia and sustained hypotenperiod of about 45 sets., it elicited Tachyphylaxis developed with consecutive sion (30 - 70%, 2 - 3 hours). administrations. At the peak of fall, bilateral vagotomy instantaneously raised the m.a.p. to normal. Bilateral vagotomy, prior to the administration of VT, substantially curtailed the duration of hypotension. VT It potentiated significantly increased the rate ,and depth of respiration. isoprenaline-induced hypotension and inhibited the pressor response to VT induced negative chronotropic and nicotine in anaesthetized rats. inotropic effects on the isolated rabbit, rat and frog heart; these were unaffected by atropine. On cat heart in situ and rat hind-limb perfusion The results suggest that VT, like there was no appreciabel action. nicotine has both ganglion stimulating and ganglion blocking properties.
CARDIOVASCULAR EFFECTS OF VITEXIN. M C. Prabhakar, H. Bano, I. Kumar, M.A. Shamsi and M.S.Y. Khan. Research Division, Institute of History of Medicine and Medical Research, P.O. Madangir, New Delhi-110062, India. Vitexin (VT), 8-C-B-D-Glucopyranosyl-apigenin, isolated from Ochrowas investigated for its carpus longifolius and Arnebia hispidissima, VT (0.01 - 1.0 mg/kg, i.v.) elicited dosecardiovascular actions. independent rise in mean arterial pressure (m.a.p.1 of anaesthetized normotensive rats. In bilaterally adrenalectomized rats, however, a dosedependent fall was observed. With higher doses (1 mg/kg), after a latent bradycardia and sustained hypotenperiod of about 45 sets., it elicited Tachyphylaxis developed with consecutive sion (30 - 70%, 2 - 3 hours). administrations. At the peak of fall, bilateral vagotomy instantaneously raised the m.a.p. to normal. Bilateral vagotomy, prior to the administration of VT, substantially curtailed the duration of hypotension. VT It potentiated significantly increased the rate ,and depth of respiration. isoprenaline-induced hypotension and inhibited the pressor response to VT induced negative chronotropic and nicotine in anaesthetized rats. inotropic effects on the isolated rabbit, rat and frog heart; these were unaffected by atropine. On cat heart in situ and rat hind-limb perfusion The results suggest that VT, like there was no appreciabel action. nicotine has both ganglion stimulating and ganglion blocking properties.