The effects of DL-tetrahydropalmatine (THP)on action potentials and contractilies of isolated giunea pig papillary muscle cells were observed with the microelecorode technique. THP(10~(-5)-3x10~(-4)M)could produce a dose-dependent negative inotropic effect. THP(0.1 mM)could shorten APD_(20) and APD_(50) evidently (p

Effects of reserpine on the physiologic properties of myocardium were studied in the auricle of quinea pig. Reserpine (10 ?M) decreased the contractive force of the left auricle to 57 ?15% (P0.05) in the left auricle of guinea pig, Reserpine shifted the dose-response curve of epinephrine positive frequency non-parallelly to the right with decrease of its maximum effect. It also possessed antagonistic effect for calcium positive frequency response. The results obtained indicate that reserpine might possesse calcium antagonistic effect.

The calcium antagonistic effect of dl-tetrahydropalmatine(THP) on isolated rat uterus was observed. THP decreased significantly uterine contraction induced by oxytocin, KCl, CaCl_2. THP nonparallelly shifted cacium chloride dose-response curve to the right, and decreased the maximal response, showing noncompetitive antagonism, PD'_2 value was 4.6. THP obviously decreased the intracellular and extracellular calcium-dependent components in oxytocin-induced contraction response. These results have shown that THP not only mainly inhibited potential dependent calcium channel, but also decreased calcium relesese from intracellular stores.

The effects of amrinone on the contraction and action potential of isolated guinca pig papillary muscles were studied with intracellular microelectrodes. When the preparations were exposed to 25 ?mol/L amrinone, their pcak developed tension(DT) was inereased by 65.4%, the maximum rate of force development (dT/dt_(max)) was increased by 50.8% the time to peak developed tension (tPT) was shortened by 15.9%. By raising the concentration of amrinone to 250 ?mol/L, DT and dT/dt_(max) were increased by 98.5% and 91.3%, respectively, and tPT was shortened by 24.7%. Concomitantly, amrinone can prolong the durations of action potential (APD50, APD90)and the effective refractory period (ERP) of the ventricular cells.These results suggest that amrinone (made in China) possesses the obvious positive inotropic effect.

The effects of metoclopramide( MCP ) on the physiologic properties of guinea pig papillary muscles and the hemodynamics in anesthetic dogs were studied. MCP decreased contractility, increased the epinephrine concentration inducing automaticity and shifted the voltage-time plot to the right. But the functional refractory period was prolonged. Furthermore, the contractility and automaticity of the right auricle were decreased. MCP 5 mg/kg iv increased cardiac index (CI), systolic blood pressure ( SBP ), diastolic blood pressure ( DBP ), left ventricular systolic pressure ( LVSP ), maximal rate of change of intraventricular pressure ( dP/dtmax ), and total peripheral resistance ( TPR ) while MCP 10mg/kg iv decreased SBP, DBP, LVSP, dP/dtmax and TPR except increase of CI.

The effects of dl-Tetrahydropalmatine ( THP ) on the physiologic properties in the auricle of guinea pig and on isoproterenol and calcium-mediated positive chronotropic action in guinea pig atria were studied.30 minutes after THP 52 nM was added, the contractility was decreased to 53+ ( SD ) 17%(P0.05) in the left auricle of guinea pig. Furthermore, the contractility and automaticity of the right auricle were decreased to 48+13% (P