DIRECT INOTROPIC ACTION OF WB-4101 AND PRAZOSIN IN THE GUINEA-PIG PAPILLARY-MUSCLE - COMPARISON WITH HOE-234, THE NEW ACTIVATOR OF ATP-SENSITIVE K+ CHANNELS

1. The alpha-1a adrenoceptor antagonist WB-4101, the alpha-1 adrenocep tor antagonist prazosin and the new activator of ATP-sensitive K+ chan nels HOE-234 were examined. The force of contraction and the rate of r ise of contraction force were measured. 2. WB-4101 and HOE-234 were fo und to produce negative inotropic action in a dose dependent manner. T his effect was attenuated by glibenclamide. On the other hand prazosin increased slightly the force of contraction and the rate of rise of c ontraction force in the same tissue. 3. The direct inotropic effects o f above mentioned substances are compared and discussed.