The effect of stimulation on the myoelectrical activity of the rectosigmoid in man.

The myoelectrical activity of the rectosigmoid has been studied in 66 subjects at rest and after stimulation with either pentagastrin 6.0 mug/kg hr intravenously in 21 cases, neostigmine 0.5 mg intramuscularly in 20 cases, or two bisacodyl suppositories in 19 cases. Two electrical rhythms were present at rest. A faster rhythm (frequency 6-9 cycles/min) predominated and its incidence was significantly increased by neostigmine at all levels in the rectosigmoid and by bisacodyl in the rectum only. The incidence of the slower rhythm (frequency 2.5-4.0 cycles/min) was significantly increased by pentagastrin which had no effect on the faster rhythm. The amplitude of each basic electrical rhythm rose when its incidence was increased. Motor waves were augmented corresponding to which of the two electrical rhythms was increased after stimulation.