Abstract: 4-Aminopyridine(4-AP),a known potassium channel blocker, was shown toinduce histamine release from mast cells in mice,After ip 4-AP 5 mg· kg^-1 the histamine contentincreased in blood, but decreased in the lung tissue。Calcium antagonists nifedipine( NIF)500mg·kg^-1ig,TMB-8 300 μmol·L^-1 in vitro and potassium channel opener minoxidil(MIN)100mg· kg^-1 inhibited the histamine release induced by 4-AP from mouse peritoneal mast cells(PMC)。These results provide evidence that potassium channels are present in mouse mast cell membranes andindicate that the mechanism of histamine release by 4-AP may be related to the potassium channelblocking effect.As the result of this effect ,the calcium channeis open and the Ca²⁺ influx to the mastcells increases,thus eliciting histamine release。