Contractile action of gastrin-releasing peptide on isolated preparations of human gastroduodenal muscle.

Mechanical activity was recorded in muscle preparations isolated from different regions of the human stomach (circular and longitudinal strips from fundus, corpus and antrum) and duodenum. Application of gastrin-releasing peptide (GRP, 10(-9) to 10(-7) mol/l) caused a concentration-dependent increase in the activity in all stomach strips, the height and the pattern of contraction was similar to the acetylcholine (ACh) responses (10(-7) to 10(-5) mol/l). Longitudinally cut duodenal strips were also excitable by GRP. Circularly cut duodenal strips, however, showed no responses to GRP. Both layers were excitable by ACh. The most prominent effect of GRP on longitudinal duodenal strips near the jejunum was a tonically appearing activation, which could reach up to 180% of the maximum ACh-induced activation.