The regional difference in the responses of the guinea pig gastric muscles to gastrin.

The responses to gastrin were studied in the circular muscles of guinea pig stomach. The muscle strips were prepared from the three different regions of the stomach; the pylorus, the antrum and the upper body. The responses to gastrin, which were concentration dependent contractions, appeared only in the preparations from the upper body. The contractile response of the upper body was observed not by the cumulative application of gastrin, but by the one show applications between which interval was 30 minutes. In contrast, any response to gastrin was not obtained in the other two regions. The contractile response to gastrin in the upper body was not affected by any antagonist, mepyramine 10(-6)g/ml, atropine 10(-6)g/ml, cimetidine 3 X 10(-5)g/ml or tetrodotoxin 10(-7)g/ml. In conclusion, it is reasonable that gastrin may act on the circular muscle of the upper body and cause the concentration dependent contraction by its direct effect.