Effect of prostaglandin E1 and indomethacin on responses of longitudinal muscle of guinea-pig ileum to cholecystokinin.

The effect of prostaglandin E1 (PGE1) and indomethacin (IND) cholecystokinin (CCK)-induced contractions of guinea-pig isolated ileum longitudinal muscle were studied. PGE1 (2.8--28 nM) consistently and dose dependently increased the contractions evoked by CCK (indirect muscle stimulation) or by ACh. IND (2.7 microM) decreased the contractions to both compounds and this was reversed with 2.8--7 nM PGE1. Pretreatment of the preparations with phentolamine (2.6 microM) or pretreatment of the animals with reserpine (2 mg/kg i.p. 24 h before killing) did not affect PGE1 potentiation or IND inhibition of CCK-induced contractions. The results indicated that PGE1 potentiated CCK-induced contractions of the longitudinal muscle of guinea-pig ileum by increasing the response to released ACh. Experiments with IND suggested that endogenous PGs may modulate the effect of CCK or related gastrointestinal hormones.