Evaluation of the refractory period of the human migrating motor complex through induction of premature Phase III

Abstract

AbstractWe examined the refractory period of the migrating motor complex and the ability of somatostatin to increase the oscillation frequency of the complex through the initiation of premature phase HI activity. Fifteen normal human subjects were studied by means of a naso‐intestinal motility probe and divided in three groups of five subjects each. After recording three spontaneous migrating motor complexes, somatostatin was infused at a time interval from the last spontaneous Phase III that corresponded to 10% (Group A), 20% (Group B) and 30% (Group C) of the previous mean cycle length. Eleven successive somatostatin infusions were given with the interval between each infusion being altered in a fashion designed to identify the refractory period of the MMC. The results show a spontaneous cycle length of 121.3 ± 15.8 min (mean ± SD). When given at 10% (12 min) of the previous cycle somatostatin did not elicit any response, when given at 20% (24 min) of the cycle somatostatin induced a premature Phase III activity in three of five subjects; when given at 30% (36 min) of the cycle somatostatin induced a premature Phase III in all five subjects examined. Each somatostatin infusion was associated with the onset of a premature Phase III activity in 50% of the trials when the time interval was 20% of the ideal cycle (24 ± 4 min). When the time interval was increased to 30% of the ideal cycle a premature Phase III could be recorded after each somatostatin infusion in all trials. Motilin and pancreatic polypeptide plasma levels were significantly lowered by somatostatin. It is concluded that the migrating motor complex of the human gastrointestinal tract shows an absolute and a relative refractory state. Repetitive infusions of somatostatin for short periods may increase the occurrence of Phase III activity up to four‐fold.