Role of prostaglandins in tone and effector reactivity of the isolated rat stomach preparation.

The influence of indomethacin (2 mug/ml) on the tone and on the response to ACh, 5-HT and tryptamine of the stomach strip preparation from normal and Essential Fatty Acid Deficient (EFAD) rats was examined. The pD2 value of ACh and 5-HT, but not of tryptamine, was significantly lower on the preparations obtained from EFAD rats than on those from normal rats. Contradictory results were obtained with respect to the influence of indomethacin on the pD2 value of ACh, 5-HT and tryptamine. No significant difference in initial tone and contractility of the stomach strips of both groups of rats was observed. However, the tone of the strips from normal rats increased with time. Preparations from EFAD rats showed a gradual decrease of the tome with time. Pre-incubation with indomethacin reduced the tone of strips from both groups of rats to a comparable extent. Thus further support is provided for the proposed role of prostaglandins in the maintenance of the tone of isolated smooth muscle. The possibility is raised that prostaglandins might not be predominantly involved in the generation of the initial tone and also not substantially contribute to the effector reactivity of the organ.