ObjectiveTo evaluate the effect of naloxone on L-type calcium current (ICa-L) in isolated rat ventricular myocytes.MethodsAdult SD rats of both sexes aged 8 weeks weighing 200-250 g were used in this study.Single cardiac ventricular myocytes were enzymatically isolated from SD rats.ICa-L was measured in ventricular myocytes and recorded using whole cell patch-clamp technique.Different concentrations (20 and 100 μg/ml) of naloxone were added to the cardiomyocytes.The effect of naloxone on ICa-L was evaluated.ResultsThe peak current of ICa-L Was inhibited by naloxone in a concentration-dependent manner.Naloxone had no significant effect on steady-state activation curve.ConclusionNaloxone inhibits the L-type calcium channel of ventricular myocytes and exerts negative effect on ventricular muscle function.

Objective To investigate the effect of propofol on the secretory function of adrenal medullary chromaffin cells of rats.Methods The rat adrenal pheochromocytoma cells cultured in vitro were seeded in 24-well plates at a density of 1×1010 cells/ml and divided into 5 groups (n=12 each) using a random number table:control group (group C),different concentrations of propofol groups (P1 and P2 groups),and different concentrations of etomidate groups (E1 and E2 groups).Propofol was added with the final concentrations of 30 and 100 μmol/L in P1 and P2 groups,respectively.Etomidate was added with the final concentrations of 4 and 40 μmol/L in EI and E2 groups,respectively.The cells were then incubated for 10 min in an incubator at 37 ℃.At the end of incubation with drugs,6 wells in each group were selected,and physiological salt solution 200 μl was added;another 6 wells in each group were selected,and high K+ physiological salt solution was added.[3 H] PSS and [3 H] K+-PSS were measured by [3 H] norepinephrine release assays.Results Compared with group C,[3 H] K+-PSS and [3 H] K+-PSS/PSS were significantly decreased in P1,P2 and E2 groups (P＜0.05),and no significant changes were found in [3H] K+-PSS and [3H] K+-PSS/PSS in group E1 (P＞0.05).Compared with group P1,[3 H] K+-PSS and [3 H] K+-PSS/ PSS were significantly decreased in group P2 (P＜0.05).Conclusion Propofol can inhibit the secretory function of adrenal medullary chromaffin cells of rats in a concentration-dependent manner.