Tadayoshi Takeuchi (1,2), Satomi Niioka (1), Michiru Yamaji (1), Yutaka
Okishio (1), Toshiaki Ishii (1,2), Hideaki Nishio (1), Koichi Takatsuji
(3) and Fumiaki Hata (1,2,*)
(1) Department of Veterinary Pharmacology, College of Agriculture, (2)
Department of Molecular Physiology and Biochemistry, Research Institute
for Advanced Science and Technology, Osaka Prefecture University, Sakai
599-8531, Japan
(3) 0saka Prefectural College of Nursing, Habikino, Osaka 583-0872, Japan
(*) To whom correspondence should be addressed (1).
Abstract: Participation of nitric oxide in the electrical field
stimulation-induced nonadrenergic, noncholinergic (NANC) relaxation in various
intestinal regions was studied in 2- to 50-week-old Wistar rats. In the
jejunum of 2-week-old rats, the extent of the nitric oxide-mediated component
of the relaxation of longitudinal muscle was approximately 60 - 70%, whereas
the component was 40 - 50% in 4-week-old rats and was absent in 8- and 50-week-old
rats. Thus, nitric oxide seems to be the most important mediator at young
ages but its significance is lost with age. The same tendency as that in
the jejunum was also shown in longitudinal muscle of the ileum, proximal
and distal colon, and rectum. The tendency was also shown in the circular
muscle of the rectum. Sensitivity of the longitudinal muscle of the jejunum
and proximal colon to exogenously added nitric oxide was high in younger
rats. Immunoreactive structures for nitric oxide synthase were observed
in the circular muscle layer of the rectum. The population of the structures
was denser in 4-week-old than that in 50-week-old. The results suggest that
NANC relaxation in every region of the intestine at 2-week-old is almost
solely mediated by nitric oxide, and its significance as an inhibitory mediator
gradually or rapidly decreases with age.
Keywords: Nitric oxide, Nonadrenergic, noncholinergic (NANC) relaxation,
Aging, Rat intestine, Nitric oxide synthase