Some possibilities for prostaglandin mediation in the contractile response to ATP of the guinea-pig digestive tract.

Several contractile responses of longitudinal muscles of the guinea-pig digestive tract to exogenously applied ATP (10-300 micrometer), including "rebound" contractions, were inhibited by indomethacin (3-20 micrometer) or polyphloretin phosphate (10-100 microgram/ml). Relaxations to ATP in stomach and large intestinal muscles were increased by these drugs. Prostaglandin release might therefore contribute to the contractile responses of the guinea-pig digestive tract to ATP.