ABSTRACT
Objective To investigate the influence of citalopram on the fast response action potential,slow response action potential,in vitro electrocardiogram(ECG) and in vivo ECG of cardiac myocytes,and explore its mechanism of adverse cardiac effects. Methods Conventional microelectrode technique was employed to record the fast and slow response action potentials of the isolated papillary muscles of guinea pigs.In vivo and in vitro ECG were recorded from anesthetized animals and Langendorff-perfused hearts,respectively. Results Citalopram could prolong the RR interval and QRS duration of in vivo ECG.The premature ventricular contraction and atrial ventricular block were induced by 12.5?10-6 mol/L citalopram.The maximum ascending velocity of 0 phase(Vmax),action potential amplitude(APA) and action potential duration(APD50 and APD90) were dose-dependently decreased by citalopram in the fast and slow response action potentials of guinea pigs,respectively. Conclusion Citalopram can inhibit sodium and calcium channels effectively,which may be the ionic mechanism that citalopram induces arrhythmia in the clinical practice.
ABSTRACT
<p><b>AIM</b>To determine the feasibility of establishing the heterologous expression model of human- serotonin transporter(hSERT or 5-HTT).</p><p><b>METHODS</b>cRNA of SERT was transcribed from cDNA, which was cloned in the pOTV vector. Each oocyte of mature xenopus laevis was injected with transcribed cRNA in vivo and incubated at room temperature for 4-9 days. Recording the current induced by 5-HT with voltage clamp technique tested the function of the expressed 5-HT transporter.</p><p><b>RESULTS</b>The transporter current could be observed in Ringer's solution containing 5-HT, and the 5-HT induced current were concentration-dependent. Norepinephrine and dopamine could not induce the transporter current while the 5-HT induced current could be specifically inhibited by 5-HTT blocker, desipramine.</p><p><b>CONCLUSION</b>The results demonstrate that the heterologous expression product in xenopus laevis oocytes is human 5-HT transporter.</p>
Subject(s)
Animals , Female , Carrier Proteins , Genetics , DNA, Complementary , Genetics , Gene Expression , Models, Animal , Oocytes , Metabolism , RNA, Messenger , Genetics , Serotonin , Metabolism , Serotonin Plasma Membrane Transport Proteins , Genetics , Xenopus laevisABSTRACT
The slowing down mechanism of heart rate during growth of the body after birth was studied in isolated rabbit heart and sinus node (SN) preparation with Langendorff perfusion method, conventional microelectrode recording and perforated patch for recording pacemaker current I(f). The radioimmunoassay was also used to measure the concentration of cAMP within SN cells. The results indicate that without the influence of nervous and humoral factors, the spontaneous heart rate would also become slower as the rabbit grew older, which is due to the decrease of spontaneous depolarized rate of phase 4 in SN cells. The negative directed shift of the threshold potential of I(f) and the decrease in cAMP concentration within SN cells may be responsible for the phenomenon. The results obtained suggest that besides the nervous and humoral factors which influence the heart rate, the changes in automaticity of SN cell itself may take part in the slowing down process as the body grows up.