The effects of @entity934 ( @entity1617 ) and K+ on tension and membrane potential were studied in order to determine the role of electromechanical and pharmacomechanical coupling in @entity1617 -induced contractions of @entity235 trachealis muscle. @entity972 causes sustained contractions of the muscle via membrane depolarization, which appears to be related in a linear manner to the log of the external K+ concentration. From the K+ experiments a curve relating membrane potential and tension was obtained. The resting membrane potential of the trachealis is -30 +/- 1 mV. At a dose of 10(-7) M @entity1617 the membrane is depolarized to about -55 mV and then at 10(-6) M @entity1617 there is more depolarization to about -40 mV. At higher doses of drug there is no further change in membrane potential. The relationship between the dose of @entity1617 and tension is much different. Contraction begins at 10(-7) M @entity1617 but does not saturate until a dose of 10(-3) M is reached. The data were interpreted by using the relationship between EM and tension from the K+ experiments and the @entity1617 dose-response curves as follows. At 10(-7) M @entity1617 only pharmacomechanical coupling is involved in the contraction. At higher drug doses both pharmaco- and electromechanical coupling are involved, but pharmacomechanical coupling appears to play a much greater role. The maximal contribution of electromechanical coupling is approximately 30% of the contraction and this occurs at 10(-6) M @entity1617 .

Role of depolarization in @entity934 -induced contractions of XXXX trachealis muscle.

@entity235 :: ('9615', 'Species') :: ['dog'] @entity1617 :: ('CHEBI:22614', 'Chemical') :: ['ACh'] @entity972 :: ('MESH:D011188', 'Chemical') :: ['Potassium'] @entity934 :: ('MESH:D000109', 'Chemical') :: ['acetylcholine']
@entity235 :: (9615,Species) :: ['dog']
