ABSTRACT
AIM To investigate the effect of 4-aminopyridine (4-AP) on ion channels of myocytes. METHODS L-type calcium channel and sodium channel currents were recorded in guinea pig single ventricular myocyte using whole-cell patch-clamp techniques. RESULTS 4-AP, 0.1, 0.5 and 1.0 mmol*L-1 were shown to inhibit L-type calcium channel currents (ICa,L) and sodium channel currents (INa) concentration-dependently. The percentage of inhibition were (11.6±1.7)%, (37.5±8.3)% and (54.5±6.9)% (P<0.01) respectively for ICa,L, and (22.1±14.3)% (P<0.05), (39.4±8.8)% and (62.3±6.8)% (P<0.01) respectively for INa. 4-AP 0.5 mmol*L-1 shifted the I-V curves of ICa,L and INa upwardly. CONCLUSION 4-AP blocked L-type calcium channel and sodium channels in guinea-pig ventricular myocytes concentration-dependently.
ABSTRACT
I sopropylmine vanillinate (IV) given iv 5 , 10 mg/kg in anesthe tized rats produced a dose-dependent decrease in mean arterial pressure and a concomitant decrease in heart rate.In pithed rats IV was unable to shift the phenylephrine doserespon-se curve to the right, but prazosine caused 53-fold shift.No direct effect of vasodilation was shown by IV on rabbit aorta strips .The concentration-response curve of isoprenaline in isolated rat right atrium was competitively inhibited by IV and propranolol. pA2 value was 4.0 for IV and 8.2 for propranolol. In addition, 'IV depressed contractility & heart rate of isolated rat atria.These results suggest that the hypotensive action of IV may be related to the decrease of HR, inhibition of contractility and slight blocking of B-adrenergic receptor. However the mechanism underlying the hypotensive effect of IV is to be further studied.
ABSTRACT
The present experiments were designed to investigate the effects of atriopeptin I on different vascular smooth muscles.Isometric tension was recorded from spiral strips of human umbilical arteries, gastro-epiploica dextral arteries, rat and rabbit aorta. Atriopeptin H showed a potent inhibitor on the contraction induced by noradrenaline ( 3tmol/l), Serotonin ( lnmol/1), hista-mine ( 10M-mol/l ) and phenylephrine ( l(imol/l)in the strips of rat and rabbit aorta, but not on the contraction induced by the above-mentioned drugs and KC1 (80mmol/l), prostaglandine F2a ( 10umol /I) in umbilical and gastroepiploica dextral arteries of human beings. Sodium nitroprussids showed also a potent antagonist on the contraction induced by noradrenaline ( 3 M-mol/1) serotonin ( 1imol/l), histamine (10imol/1) and prostaglandine F2a (10nmol/l) in the strips of umbilical arteries.lt produced concentration-dependent inhibition of the contraction induced by noradrenaline.It could remarkably decrease the resting tension of the strips.The present results suggest that atriopeptin I exhibits a similar vasodilator profile in rat and rabbit aorta as that found for sodium nitroprusside in the human umbilical arteries.The ineffectiveness of atriopeptin I on human umbilicalj and gas-troepiploica dextral arteries is in marked contrast to the effectiveness of sodium nitroprusside in the human umbilical arteries, indicating that the action of atriopeptin f possesses species difference.
ABSTRACT
AIM To study the effects of Lotusine(Lot), a pure alkaloid extracted from the green seed embryo of Nelumbo nucifera Gaertn, on the action potentials(APs) in myocardium and slow inward current(Isi) in cardiac Purkinje fibers(PF). METHODS standard microelectrode and two microelectrodes voltage clamp techniques were used. RESULTS Lot 1～100 ?mol?L -1 could concentration dependently prolonged APD 20 and APD 90 of fast AP and increase the contractile force(Fc) in guinea pig papillary muscles. In papillary muscles pretreated with reserpine, similar results were also observed but the effect of Lot was weaker than those pretreated without reserpine. In guinea pig left atria, Lot 30 ?mol?L -1 could partly antigoniste the shortening APD effect of acetylcholine. Lot 3～100 ?mol?L -1 could enhance the action potential amplitude(APA)and maximal velocity of phase 0 depolarization ( V max ) of slow AP of papillary muscles induced by high K + (24 mmol?L -1 )and isolated sinoatral node(SAN) pacemaker cells of rabbits with dose dependent manner,But not obvousely short the sinus cycle length of SAN. Moreover, Lot increased the Isi of in canin cardiac PF with with time dependent and dose dependent manner. CONCLUSION The results suggest that Lot has effect of prolongation of APD and increase of Ca 2+ influx and these are very important in contribution to its positive inotropic effect, which may be related to inhibition of phosphodiesterase Ⅲ.
ABSTRACT
IQ86034 (5.3).In addition, the blocking action of 4 isoquinoline derivatives on ?1 and ?2 adrenoceptors was similar to that of benzoquinolizine derivatives.