The newly isolated peptide,urocortin(UCN)has been found to have potent cardioprotective effects.In order to investigate the effectof UCN on L-type calcium currents(ICa,L),exploring the mechanisms of UCN’s cardioprotective effects,we directly measured the ICa,Lin the adult rat cardiac myocytes exposed to UCN using standard whole-cell patch-clamp recording technique.Our results showed that UCN exerted decreasing effects on the ICa,L of the single adult rat cardiac myocytes.The current density was inhibited by about 35% after exposure of the cells to UCN(0.1 mol L−1)for 10 min,from the control value of 7.19±1.44 pA/pF to 4.74±0.75 pA/pF(n=5,P<0.05).This ICa,L-inhibiting action of UCN was concentration dependent.Moreover,no frequency dependence of UCN effects on ICa,L was observed.In combination with previous reports,our results suggest that there might be a close relationship between the cardioprotective effects of UCN and L-type calcium channels.