Abstract: Aim To study the effects of Buflomedil hydrochloride (BUF)on the fast action potential (AP)of isolated guinea pig papillary muscles.Methods It racellular microelect rode technique was used to investigate the effects of different BUF concentrations on AP.Results different concent rations of BUF significantly reduced the amplitude of action potential (APA) and shortened the action potential duration (APD)on the levels of APD 30 and APD 50 APD 90 was also evidently shortened by BUF 10^-4 M and 10^-3M.The onset of the action was relatively delayed by BUF 10^-4M.BUF 10^-3M and 5×10^-3M exerted their actions more quickly and induced a concent ration-dependent decrease in the excitability of papillary muxcles.BUF 5×10^-3 M cont inued decreasing the absolute value of rest ing po tent ial (RP)after it abolished AP.Conclusions (1)BUF inhibit Ca²⁺, Na⁺ channels of guinea pig papillary muscles.The action mechanisms of BUF on K⁺channels a recomplicated.(2)BUF could reduce the excitability of guinea pig papillary muscles to elect rical field stimulation.(3)The inhibitory effects of BUF on AP are reversible.

Key words: buf lomedil hydrochloride (BUF), guinea pig, papillary muscle, action potential (AP)