Sensitization by (+) Inpea of rat stomach strip contraction induced by PGE2 or pleural exudates

Potentiation by phenolphthalein of the responses of guinea-pig ileum and rat stomach strip to PGE2 and other agonists

Phenolphthalein was examined for its effect on the activity of isolated muscle (guinea-pig ileum and colon, rat stomach), and on the tissue responses to PGE2, histamine and 5-HT. The ileal circular muscle and both muscle layers of the colon were unaffected by phenolphthalein. In contrast, the laxative potentiated the responses of the longitudinal muscle of guinea-pig isolated ileum and the rat stomach strip to the agonists, particularly PGE2. This potentiation was reduced by indomethacin in vivo, but mepyramine or methysergide had little or no effect. Augmentation of muscle activity by phenolphthalein, particularly in the response to PGE2, may contribute to the laxative effect.

Enhancement by levamisole of the contractions induced by prostaglandin E2 in the guinea-pig isolated ileum

The effect of levamisole on prostaglandin E2 (PGE2)-evoked contractions was studied on guinea-pig isolated ileum. Addition of levamisole (10 micrograms/ml) to the organ bath produced a pronounced increase in the amplitude of the PGE2-evoked responses. Levamisole (10 micrograms/ml) also sensitized the guinea-pig isolated ileum to 5-hydroxytryptamine and bradykinin, but not to histamine. The effect of the levamisole was not due to stimulation of autonomic ganglia or cholinergic activity since it was unaffected by hexamethonium or atropine, but it was prevented by indomethacin.