An experimental study on the effect of irradiation on motility of the small intestine]

In order to investigate the pathological condition of the intestinal tract after irradiation, experimental radiated intestinal tracts were prepared in adult rabbits, and motile functions of the terminal ileum of these rabbits were observed under electromyography. The results were also examined in relation to histological changes in corresponding region. The following results were obtained: 1. In the irradiation groups, findings different from the non-irradiation group were observed corresponding to the irradiation dose and time after the irradiation. 2. No correlation was observed between basic electric rhythm (BER) and irradiation dose. However, BER showed a slight decreasing tendency over time. 3. The active phase duration times in the irradiation groups were prolonged up to an irradiation dose of 80 Gy, then shortened in groups radiated with 120 Gy or more, as compared with the non-irradiation group. 4. The frequency of antiperistaltic propagation of electric stimuli showed an increasing tendency as the irradiation dose increased. 5. Dysrhythmia of electric discharge observed in the irradiation groups was enhanced by increase in irradiation doses and over time. 6. Motile function of the intestinal tract was enhanced in groups radiated up to 80 Gy and inhibited in groups radiated with 120 Gy or more. 7. In the 80 Gy irradiation group, motile function of the intestinal tract was enhanced at early phases after irradiation and inhibited at later phases. 8. Radiated intestinal tracts showed increasing tendencies in stimulation thresholds against agents such as Neostigmine and PGF2 alpha. 9. Histological changes in the intestinal wall were more marked in the mucous side. As the irradiation dose increased, the degrees of disorders were enhanced. At the early phases in the irradiation groups, inflammatory changes were the major histological changes seen. At later phases, chronic organic changes in the muscular layers, especially consisting of destruction of intermuscular plexus and degeneration decrease in ganglion cells, were marked. These irreversible changes were suggested to influence abnormalities in the motile function of the intestinal tract.