ATP-sensitive K+ channels (KATP) were not identified in gastric smooth muscle cells. However， in tension recording of intact gastric circular muscle， lemakalim of KATP channels opener in other tissues suppressed mechanical contractions and this effect was blocked by glibenclamide， a specific inhibitor of KATP channels. The aims of this study were to investigate whether KATP channels exist in gastric smooth muscle of guinea-pig and to know its physiological role. Whole cell K'+ curr‘ents activated by lemakalim were recorded from freshly isolated cells with a 0.1 mM ATP， 140 mM KCl pipette solutions. Lemakalim (10 μM) increased inward currents of -224:t34 pA (n=13) at -80 mV of holding potential in bath solution contained 90 mM K'+ . Bath-applied glibenclamide (10 μM) inhibited the lemakalim-activated inward currents by 91:t 6% (n=5). These lemakalim-activated inward currents were reduced by increased intracellular ATP from 0.1 to 3 mM (-41:t 12 pA) (n=5). The reversal potential of the glibenclamidesensitive inward currents was -5.2:t2.4 mV (n=3) in external 90 mM K+ and shifted to -14.8:t3.6 +