OBJECTIVE To compare the effect of four 5-hydroxytryptamine type 4 (5-HT4) receptor agonists:cisapride,zacopride,macopride and 2-[1-(4-piperonyl) piperazinyl]-benzothiazole (BZTZ),on rat cardiac inward rectifier potassium channel (IK1)and heart rhythm.METHODS The whole-cell configuration of patch-clamp technique was used to record effects of 5-HT4 receptor agonists onIk1 in enzymatic dissociated rat ventricular myocytes or Kir2.1 transfected HEK 293 cells.Western blotting was used to observe the expression of Kir2.1 channel exposed 24 h to agents in ventricular myocytes.Langendorff-perfused hearts were perfused with four agents respectively for 30 min.The electrocardiogram was recorded simultaneously.RESULTS BZTZ,cisapride and mosapride 0.1-10 μmol· L-1 decreasedIk1 in a concentrationdependent manner.At the same concentration (1 μmol· L-1),BZTZ showed the most potent inhibition onIκ1 (P＜0.01),followed by cisapride.Mosapride showed slight inhibition efficiency.However,zacopride enhanced Iκ1 (P＜0.01).In Kir2.1 heterologous expression systems,zacopride activated Kir2.1 current (P＜0.01) while mosapride had no effect.In ex vivo Langendorff-perfused hearts,BZTZ and cisapride 1μmol· L-1 elicited singnificant rhythm disturbances,and the total of premature ventricular beats (PVB) were 159±28 and 61±13.50％ (4/8) (P＜0.05) and 25％ (1/8) of the hearts exhibited ventricular tachycardia (VT),while 37.5％ (3/8) and 12.5％ (1/8) of the hearts exhibited ventricular fibrillation (VF),respectively.Mosapride and zacopride had no side effects on heart rhythm.Zacopride also suppressed BZTZ-or cisapride-induced arrhythmias.BZFZ had the strongest proarryhthmic potency among the 5-HT4 agonists,followed by cisapride,mosapride and zacopride.CONCLUSION Iκ1 might be an independent risk factor for arrhythmogenesis and a new target for screening safe 5-HT4 receptor agonists and gastrointestinal prokinetic agents.

Aim To investigate the inhibitory effects of zacopride(Zac) on arrhythmia induced by isoproterenol ( ISO) and the underlying mechanisms in rats. Meth-ods ①ECGs were recorded in anesthetized rats in vi-vo to observe the effects of zacopride on arrhythmia in-duced by ISO. ② Intracellular microelectrode tech-nique was used to investigate the effects of zacopride on resting membrane potential, delayed afterdepolariza-tions ( DADs) and triggered activity ( TA) induced by ISO combined with 3. 6 mmol·L-1 CaCl2 in right ven-tricular papillary muscle of rats. Results ① In ISO group rats, ventricular premature beats ( VPB ) oc-curred frequently with ST-segment depression. Com-pared with ISO group, the incidence of VPB in ISO+Zac group decreased from 100% to 50% ( n=6 , P<0. 05 ) and the total number of VPB recorded in 1 hour significantly reduced from 1 574 ± 521 to 33 ± 40 ( n=6,P<0. 05). ② Zacopride at 1 μmol·L-1 could hy-perpolarize the resting membrane potential of right ven-tricular papillary muscle in normal rat from ( -74. 42 ± 1. 95 ) mV to ( -78. 50 ± 2. 07 ) mV ( n =6 , P <0. 05). ③ Zacopride at 1 μmol·L-1 significantly de-pressed the DADs and TA induced by ISO combined with 3. 6 mmol·L-1 CaCl2 in right ventricular papilla-ry muscle. The incidence of DADs decreased from 93. 75% in rats in ISO group to 25% in ISO +Zac group ( n =16 , P <0. 05 ) , and this antiarrhythmic effect could be reversed by 1 μmol·L-1 BaCl2 . Conclusions Zacopride, a selective IK1 channel ago-nist , can significantly inhibit cardiac arrthymia induced by ISO in rats, the mechanism of which is mainly at-tributed to zacopride-induced hyperpolarization of the resting membrane potential and subsequent suppression of DADs and TA via enhancing IK1 . These results pro-vide further evidence that to enhance IK1 moderately may be a feasible pathway for antiarrthymic therapy.

Aim To examine the effect of zacopride,a specific inward rectifier potassium channel(IK1)agonist,on L-thyroxine(T4)-induced ventricular remodeling and the underlying mechanism.Methods SD rats were randomly divided as control,L-thyroxine(L-thy,1 mg·kg-1·d-1,ig,10 d)model,L-thy +zacopride(5,15,50 μg·kg-1,respectively,ip),L-thy+zacopride(15 μg·kg-1)+chloroquine(7.5 μg·kg-1,ip)and L-thy+captopril(100 mg·kg-1·d-1,drinking water)groups.Echocardiography and cardiac hypertrophic indexes were measured to confirm the establishment of the ventricular remodeling model.The changes of IK1 and L-calcium current(ICa-L)were detected by whole cell patch clamp technique.The confocal microscopy and fluorescent indicator Fluo-4 were applied to examine the intracellular Ca2+ concentration([Ca2+]i)of isolated adult rat ventricular myocytes.Results L-thyroxine induced left ventricular hypertrophy with increased ratio of heart weight(HW)to body weight(HW·BW-1),ratio of left ventrical weight(LVW)to body weight(LVW·BW-1),left ventricular dimension in diastole(LVIDd),left ventricular dimension in systole(LVIDs),interventricular septum thickness(IVS)and decreased ejection fraction(EF),fractional shortening(FS)(P<0.01).Patch clamp data suggested IK1 was downregulated,while ICa-L was upregulated(P<0.01).In isolated adult cardiomyocytes,L-thyroxine increased the cell area and [Ca2+]i(P<0.01).Zacopride treatment obviously alleviated cardiac remodeling,improved cardiac function,reversed the changes of IK1 and ICa-L,and significantly attenuated intracellular calcium overload(P<0.01).The optimum dose of zacopride in vivo was 15 μg·kg-1 at which the effect was compared favourably with captopril,a classical anti-remodeling agent.Low-dose IK1 atagonist chloroquine could reverse the effect of zacopride(P<0.01).Conclusion Via activating IK1,zacopride could significantly decrease Ca2+ influx and intracellular calcium overload thereby inhibiting L-thyroxine-induced cardiac ventricular remodeling.

OBJECTIVE： To establish a method for simultaneous determination of α-pinene， β-pinene， limonene and α-terpineol in volatile oil of Forsythia suspensa. METHODS： GC method was adopted. The determination was performed on HP-5 capillary column through temperature-programmed route. The inlet temperature was 230 ℃， and detector temperature was 250 ℃； split sampling was applied （split ratio of 8 ∶ 1）； the air flow rate was 300 mL/min， the hydrogen flow rate was 30   mL/min， the tail gas flow rate was 30 mL/min， and the injection volume was 1 μL. Using limonene as internal reference， relative correction factors of α-pinene， β-pinene and α-terpineol were established， and the reproducibility of relative correction factors were investigated by using different chromatographs and columns， and chromatographic peak location of components was measured. The contents of above components were calculated with QAMS， and then compared with the results of external standard method. RESULTS： The linear range of α-pinene， β-pinene， limonene and α-terpineol were 16.5-990.0， 38.1-2 287.5， 8.2-491.2， 2.4-142.5  μg/mL， respectively （r≥0.999 1）. RSDs of precision， reproducibility and stability tests were all lower than 3％ （n＝6）. Average recoveries were 99.7％-105.5％（RSD＜4％，n＝9）. Compared with limonene （1.00），the average relative correction factors of α-pinene， β-pinene and α-terpineol were 0.91，0.86 and 1.11（n＝3）； relative retention time were 0.69-0.74， 0.81-0.86， 1.25-1.35（RSD＜3％，n＝3）. By using different chromatographs and columns， RSDs of relative correction factors were 0.21％-4.65％（n＝6）. Compared with external standard method， determination results of above 4 components were consistent （the absolute value of relative error were all less than 7％）. CONCLUSIONS： QAMS can be used for simultaneous determination of 4 kinds of effective components in volatile oil from F. suspensa.