Effects of neferine on isolated rabbit myocardium

Neferine (Nef), an alkaloid extracted from the green bud of Nelumbo nucifera Gaertn. possesses anti-arrhythmic action, Its effects upon the physiologic properties and the positive staircase and post-rest potentiation of myocardium were studied on isolated rabbit papillary muscles or left atria. 30 min after adding neferine 30 vmol/L, the contractility of the papillary muscle decreased from l00% of control to 60+-SD 10% and the duration-intensity curve was shifted to the right (indicating the decrease of excitability, p<0.01) while the concentration of epinephrine inducing automaticity was increased 12+-1 times (p<0.01) and the functional refractory period (FRP) was prolonged from 196+-8 ms to 238+-4 ms (p<0.01). 10 min after neferine 0.3 mmol/L was administrated the positive staircase of the left atrium was markedly inhibited, and the post-rest potentiation was decreased to 27+-16% 20 min later. The negative inotropism and the inhibition of the automaticity. positive staircase and post-rest potentiation suggest that neferine may influence Ca2+ movement, while the suppression of excitability and prolongation of FRP indicate that it may be due to its inhibition on Na+ influx.