BACKGROUND: Opioids and nitric oxide (NO) are functionally linked in the regulation of intestinal motility. OBJECTIVES: To investigate the role of NO in the opium induced bowel dysfunction in mice. METHODS: Sixty-six male mice received incrementally doses of the following treatments in six groups for 5 consecutive days: 1) Opium (0.2, 0.3, 0.4, 0.5 and 0.6mg/30g/day), 2) N-nitro-L-arginine methyl ester (L-NAME, 5,7.5,10,15 and 20mg/kg/day), 3) L-arginine (5-20mg/kg/day), 4) Opium+L-NAME, 5) Opium+L-arginine and 6) distilled water. At the end of the treatment, the abdomen was opened; some pieces of duodenal and proximal colon were taken to determine NO synthase (NOS) expression and nitrite levels, and some isolated rings from those parts of small and large intestine were prepared and transferred to the organ bath system to study intestinal motility. RT-PCR was used to determine the NOS gene expression. To determine the small intestinal transit, 30 mice in six groups, were used for oral administration of charcoal+gum in vivo. RESULTS: Opium decreased amplitude of the duodenum and ileum contractions, but increased frequency of duodenal and mid colon contractions (P<0.05). While the gene expression of inducible, neuronal and endothelial NOS was increased in colon (P<0.05), a reduced neuronal and endothelial NOS gene expression was shown in duodenum. The charcoal+gum transit was decreased in opium-treated animals compared to the control group (19.9%). However, L-arginine increased this transit while L-NAME decreased it. CONCLUSIONS: Opium induced intestinal smooth muscle spasms, which result in the decreased intestinal movements. The alterations in NOS gene expression may be a compensation mechanism against opium-induced intestinal dysfunction.

A volvulus is a twisting of the intestine on its mesenteric axis that could result in bowel obstruction and ischemic injury. Here the authors report a case of intestinal volvulus in a 20 years old captive hippopotamus (Hippopotamus amphibius, Linnaeus, 1758), the first well described case in this specie. The animal died suddenly after a previous history of diarrhea. At post mortem examination the animal presented a good body condition and abdominal distention. Upon opening of the peritoneal cavity, a large twisted segment of small intestine was observed. The segment rotated on its mesenteric axis and was dilated with gas and fluid and with dark red coloration, due to hemorrhage. The cause of death was intestinal volvulus. Its diagnosis is a challenging to veterinary surgeons due to the progressive onset of the symptoms that can delay the both diagnosis and the treatment thus resulting in progressing to the acute fulminating type with bowel infarction and death.