Effect of rikkunshito on gastric sensorimotor function under distention

The herbal medicine rikkunshito is effective for the treatment of gastrointestinal symptoms in patients with functional dyspepsia. Although some basic studies on the effects of rikkunshito have been reported in rats, its effects on human gastric function have not yet been clarified. Psychosocial stress induces visceral hypersensitivity and elements of rikkunshito may reasonably affect or suppress this process. We conducted a study to verify the hypothesis that rikkunshito improves stress-induced gastric hypersensitivity and/or changes in gastric wall tone.

Nine healthy volunteers (five males, four females) participated in the study. The counterbalanced regimen consisted of a 2-week period of oral administration of 7.5 g day(-1) rikkunshito, then a 2-week period without treatment. Fundic sensorimotor function was examined using a gastric barostat twice on the day after each period. Virtual reality stress was imposed during the measurements of gastric tone and electrocardiogram.

Stress induced a significant increase in heart rate (P = 0.041), gastric volume (P = 0.008), and phasic volume events (P = 0.049) and a decrease in sensory (P = 0.038), discomfort (P = 0.011), and pain (P = 0.041) thresholds of the stomach. Rikkunshito significantly reduced epigastric fullness (P = 0.037) and perceived stress (P = 0.034) following stimulation of the pain threshold, regardless of stress without the drug. Stress reduced gastric volume at the sensory threshold and increased anxiety at the discomfort threshold, and these responses were significantly inhibited by rikkunshito (P = 0.026, P = 0.022, respectively).

These findings suggest that rikkunshito may improve symptoms and impaired gastric accommodation under distention stimuli of the proximal stomach superimposed by stress.