[Involvement of nitric oxide, which was synthesized by constitutive nitric oxide synthase, and prostaglandin on diarrhea induced by castor oil in rats]

Anti-diarrhoeal activity of the latex of Calotropis procera

The dry latex (DL) of Calotropis procera (Asclepiadaceae), a potent anti-inflammatory agent has been evaluated for anti-diarrhoeal activity. Like atropine and phenylbutazone (PBZ), a single oral dose of DL (500 mg/kg) produced a significant decrease in frequency of defecation, severity of diarrhoea and afforded protection from diarrhoea in 80% rats treated with castor oil. To understand the mechanism of its anti-diarrhoeal activity, we further evaluated its effect on intestinal transit, castor oil induced intestinal fluid accumulation (enteropooling) and electrolyte concentration in the intestinal fluid. DL produced a decrease in intestinal transit (27-37%) as compared to both normal and castor oil treated animals. Unlike atropine, DL significantly inhibited castor oil induced enteropooling. However, it did not alter the electrolyte concentration in the intestinal fluid as compared to castor oil treated rats.

Effect of zaldaride maleate, an antidiarrheal compound, on intracellular cyclic nucleotide-mediated intestinal ion secretion in rats

The purpose of this study is to clarify the mechanisms of action of zaldaride, a calmodulin inhibitor. 16,16-Dimethyl prostaglandin E(2), forskolin, 8-bromo cAMP, nitroprusside, 8-bromo cGMP and Escherichia coli heat-stable enterotoxin STa increased the short-circuit current in rat colonic mucosa. Zaldaride at >/=10 microM significantly attenuated the 16,16-dimethyl prostaglandin E(2) and Escherichia coli heat-stable enterotoxin STa-induced increase in short-circuit current; whereas it did not affect other secretagogues-induced effects. These results suggest that zaldaride inhibits the activation of Ca(2+)/calmodulin-sensitive adenylate cyclase or guanylate cyclase linked to a receptor.

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 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.