PGF2 alpha on drug-induced contractile responses of frog rectus abdominis muscle.

In the present study, augmentation of contractile responses to acetylcholine, potassium chloride and caffeine by prostaglandin F2 alpha on frog rectus abdominis muscle is documented. The PG-induced responses to ACh was restricted to brief exposure of the tissue to PG. Prolonged exposure resulted in disappearance of the enhancing effect and depression of ACh responses. The augmentation of ACh response was unaltered in presence of physostigmine and the pA2-value of d-tubocurarine was not changed by PGF2 alpha ruling out the involvement of a cholinergic mechanism. In potassium depolarized muscle, PGF2 alpha abolished the contractile response to caffeine, indicating an action at the trigger calcium site. PGF2 alpha also permitted reactivation contracture during repolarization.