THE EFFECTS OF TIME AND INDOMETHACIN ON CONTRACTILE RESPONSES OF THE GUINEA‐PIG GALL BLADDER in vitro

Abstract

1 The effects of time and of indomethacin on contractile responses of the guinea-pig gall bladder were studied in vitro. 2 The tissues contracted to field stimulation at 5 Hz (in the absence and presence of atropine 10⁻⁶ m), (-)-noradrenaline (10⁻⁵ m), acetylcholine (10⁻⁵ m), and adenosine 5′-triphosphate (ATP, 10⁻⁴ m); the magnitude of the contractile responses increased with time. 3 (-)-Isoprenaline 10⁻⁵ m either relaxed (17 of 23 preparations tested) or had no effect on gall bladder strips. 4 The responses of strips of guinea-pig gall bladder to field stimulation at 5 Hz (in the absence or presence of atropine 10⁻⁶ m), (-)-noradrenaline (10⁻⁵ m), and acetylcholine (10⁻⁵ m) obtained 4 h 45 min after setting up the tissue were reduced following incubation with indomethacin (7.9 times 10⁻⁶ m for 1 h). The responses to (-)-isoprenaline (10⁻⁵ m) and to ATP (10⁻⁴ m) were abolished by incubation with indomethacin. 5 These results suggest that, in the guinea-pig gall bladder in vitro, the magnitude of the contractile responses to field stimulation at 5 Hz, (-)-noradrenaline (10⁻⁵ m), and acetylcholine (10⁻⁵ m) and the ability of the tissue to respond to (-)-isoprenaline (10⁻⁵ m) and ATP (10⁻⁴ m), may be dependent on the synthesis of a prostaglandin-like substance.