POSTNATAL DEVELOPMENT OF SLOW WAVES IN THE RAT ILEOCECUM

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  • ENDOU Toshiyuki
    Department of Physiology, Showa University School of Medicine Department of Medicine, Division of Gastroenterology, Showa University Fujigaoka Hospital
  • IIZUKA Makito
    Department of Physiology, Showa University School of Medicine
  • HASEGAWA Yoshimasa
    Department of Physiology, Showa University School of Medicine
  • OKUMA Naoki
    Department of Physiology, Showa University School of Medicine
  • OKA Atsushi
    Department of Physiology, Showa University School of Medicine
  • YAGURA Saki
    Department of Physiology, Showa University School of Medicine
  • YOSHIKAWA Akira
    Department of Physiology, Showa University School of Medicine
  • ONIMARU Hiroshi
    Department of Physiology, Showa University School of Medicine
  • KANAMARU Mitsuko
    Department of Physiology, Showa University School of Medicine
  • IZUMIZAKI Masahiko
    Department of Physiology, Showa University School of Medicine

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Other Title
  • ラット回盲部におけるslow waveの生後発達
  • ラットカイ モウブ ニ オケル slow wave ノ セイゴ ハッタツ

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Abstract

Abnormalities of intestinal motor function cause various diseases such as idiopathic intussusception, which frequently occurs during the neonatal period. The most frequent site is the ileocecum, although the reason remains unclear. The small intestine’s smooth muscle exhibits slow waves, and these are the electrical basis for intestinal motility. We hypothesized the following: 1） the amplitude and frequency of the slow waves are unstable in the neonatal period due to the immaturity of the enteric nervous system, and 2） such instability could increase the probability of intussusception. Here we examined the postnatal development of slow waves in isolated ileum-cecum preparations obtained from rats at postnatal days （P） 0-2, 6-8, 13-15, 20-22 and adulthood. Electrical activities were recorded from the distal ileum and ileocecal junction via glass suction electrodes. At P0-2, the distal ileum’s electrical activity was small, irregular, and difficult to discriminate from background noise. At and after P6-8, discernable slow waves were observed, and those cycle periods and amplitudes did not significantly change with age. However, the coefficient of variation of the cycle period and amplitude decreased with age and reached the adult values at P20-22. Slow waves were not recorded from the ileocecal junction at any age, with the exception of some preparations from adults. Since the amplitudes of slow waves observed in some adult ileocecal junctions were small, these waves could have represented contamination from an adjacent ileum. Thus, the slow waves could not be involved in the regulatory mechanism of the motor activity in the ileocecal junction. The results obtained from the distal ileum were thus concordant with our hypothesis.

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