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 x 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.