Involvement of nitric oxide from nerves on diarrhea induced by castor oil in rats

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