Jpn. J. Pharmacol. 82 (2), 168-170 (2000)

Involvement of Nitric Oxide From Nerves on Diarrhea
Induced by Castor Oil in Rats

Masayuki Uchida¹, Yumi Kato¹, Kei Matsueda², Ryousuke Shoda², Akira Muraoka² and Shigeru Yamato<sup>2


1</sup>MeijiﾊInstitute of Health Science, Naruda 540, Odawara, Kanagawa 250-0862, Japan
²InternationalﾊMedical Center, Internal Medicine, Division of Gastoroenterology, Toyama 1-21-1, Shinjuku-ku, Tokyo 162-8655, Japan

Abstract: Nitric oxide (NO) is involved in the mechanism of castor oil-induced diarrhea. This study was performed to elucidate the source of NO. Diarrhea was induced by oral administration of castor oil in rats. Diarrhea was significantly inhibited by the pre-treatment with a relatively selective nerve NO synthase inhibitor, 7-nitroindazole. This effect was attenuated by the treatment with L-arginine. Capsaicin-sensitive afferent nerve degeneration did not affect the diarrhea. N^G-Nitro-L-arginine methylester significantly inhibited diarrhea even in capsaicin-pretreated rats. These data suggest, at least in part, the involvement of NO from nerves on the diarrhea induced by castor oil in rats.

Keywords: Castor oil, 7-Nitroindazole, Capsaicin-sensitive afferent nerve