The Effect of Water Immersion Stress on Late Phase Isolated Stomach Fundus Strip Motility of Rat

Gastric ulcer is the result of imbalance between the effect of protective and destructive factors on gastric mucosal layer. There are so many proposed destructive factors including acid, bile, nonsteroidal anti-inflammatory drugs(NSAIDS) and increased gastric motility. In this study we examined the time course effect of water immersion stress on gastric motility. Male wistar rats were immersed in 20-25˚C water for 2 hours. After water immersion the rats were sacrificed at 30 min, 1 h, 6 h, 12 h and 24 h intervals and the stomaches were excised. Transverse strips of the fundus region were prepared and placed in organ bath containing modified Krebs solution perfused with carbogen gas(95% O2, 5% CO2) at 37˚C. The contractile activity of the strip was recorded using an isotonic transducer(preload 2g) on NarcoBioSystem physiograph. The amplitude and frequency of the spontaneous contractions were compared to their relevant control groups using student t-test(Pvalue<0.05). No significant change was noticed between the water immersion stress groups and their relevant controls except in 24 h group. The amplitude of spontaneous contractions increased by 161%. In previous studies it has been shown that shortly after water immersion stress, gastric mortility increases in live rats. In the isolated fundus strip model, it was noticed that the increase in contractile activity of the stomach occurred only 24 hours after water immersion stress. This may lead us to the conclusion that there are gastric as well as nongastric factors involved in water immersion induced gastric hypermotility. Nongastric factors(e.g. vagus nerve, systemic hormones and …) act rapidly and their effect can be seen shortly after the stress in live animal models. However, in isolated fundus strip model, which is free from nongastric factors, a late increase in gastric motility can be seen. This may be due to the synthesis of cell made products like Immediately Early Genes(IEGs), Heat Shock Proteins(HSPs) and so on. Further work is needed to prove this theory.