RESUMO
Berberine could reverse the phenylephrine-induced contraction of aortic strips of rabbits, but not those induced by histamine, serotonin and high-K. It showed no effect on the resting tension of the strips.Prazosin l ?M completely abolished the phenylephrine-induced contraction of the strips, but berberine 100 ?M could block 94 ? 9%.The IC50 of berberine and prazosin for phenylephrine-induced c-ontraction is 30 ?M and 0.2 ?M. The results suggest that the action of berberine is not similar to sodium nitroprusside, but is similar to prazosin, a selective ?1 adrenoceptor blocker, although its potency is less than prazosin.
RESUMO
The mechanism of antiarrhythmic effects of palmatine( Pal), an benzoquinolizine compound were studied in experimental animals.In the isolated guinea pig papillary muscles, Pal 50 ?mol/L markedly prolonged the functional refractory period(FRP)and decreased the automaticity induced by adrenaline, but exerted no effect on excitabj- iity and contractility of the muscles.Pal(10 ?mol/L ) prolonged both APD20 and APD90 of the action potential of guinoa pig papillary muscles. The Vmax was decreased at 100 ?mol/L Pal, but the action potential amplitude( APA ) and resting potential ( RP ) were unaltered.The antiarrhythmic action of Pal may be due to its ability to decrease automaticity and to proloagate FRP and APD of the myocardium.
RESUMO
Tetrandrine, a bis-benzy 1-i soqui noline alkaloid isolated from Radix Stephania tetrandra S. Moor, was proved to be a calcium antagonist. Its effects upon the heart conduction system were investigated in anesthetized rabbits.Tetrandrine 8 mg/kg iv could prolong the sino-atrial conduction time & the sinus node recovery time from 50 ? 13 ms & 286? 36 ms to 75?19 ms ( n= 8 , P
RESUMO
Jat(lOmg/kg iv) administered 5 min prior to ligation of left anterior descending coronary artery significantly decreased the incidence of arrhy-thmias(VT and VF)and mortality of rats during ischaemia and reper-fusion.It also delayed the onset and shortened the duration of arrhythmias. The size of myocardial infarction caused by coronary artery ligation was decreased by Jat ( 0.75mg/kg iv. 1 h before and 6 h after operation) in rabbits.