Gz- and not Gi-proteins are coupled to pre-junctional μ-opioid receptors in bovine airways

We investigated the signal transmission pathway by which activation of μ-opioid receptors attenuates acetylcholine (ACh) release in bovine trachealis. Electrical stimulation (ES)-induced [³H]-ACh release was determined in bovine tracheal smooth muscle strips pre-incubated with either the Gi-protein inhibitor pertussis toxin (PTX, 500 ng/ml and 1 μg/ml) or the Gz-protein specific inhibitor arachidonic acid (AA, 10⁻⁶ M and 10⁻⁵ M) and then treated with DAMGO (D-Ala²,N-MePhe⁴,Gly-ol⁵-enkephalin) 10⁻⁵ M. Indomethacin 10⁻⁵ M was used to block AA cascade. The inhibitory effect of DAMGO on ES-induced [³H]-ACh release was PTX-insensitive, but, by contrast, ablated by AA in a concentration-dependent manner. AA 10⁻⁵ M alone reduced [³H]-ACh release, an effect that was prevented by iberiotoxin 10⁻⁷ M, suggesting an involvement of Ca²⁺-activated K⁺-channels. Western blot analysis consistently showed immunoreactive bands against a specific antibody anti-Gz-α subunit at ∼40 kDa, consistent with the presence of Gz-protein. The present findings suggest that in isolated bovine trachealis, activation of μ-opioid receptors inhibits ACh-release through a signal transmission pathway involving Gz-protein rather than Gi-protein.     

Investigation of small bowel in pediatric Crohn's disease

Investigation of the small bowel has been traditionally a challenge for pediatric gastroenterologists due to its location, anatomical tortuosity, and invasiveness of the available techniques. Recently, there has been a remarkable improvement in imaging and endoscopic tools aimed at exploring successfully the small intestine in inflammatory bowel disease. The former are represented by ultrasonography (either alone or with administration of oral contrast agents) and by magnetic resonance: both have provided accurate methods to detect structural bowel changes, diminishing patient discomfort and precluding radiation hazard. The use of traditional radiologic techniques such as fluoroscopy have been markedly reduced due to radiation exposure and inability to depict transmural inflammation or extraluminal complications. Among the novel endoscopic tools, capsule endoscopy and balloon-assisted enteroscopy have tremendously opened new diagnostic and therapeutic perspectives, by allowing the direct visualization of small intestinal mucosa and, through enteroscopy, histological diagnosis as well as therapeutic interventions such as stricture dilation and bleeding treatment. These endoscopic techniques should always be preceded by imaging of the intestine in order to identify strictures. This review describes the most recent progress with the employment of novel imaging and endoscopic methodologies for investigating the small bowel in children with suspected or established Crohn's disease.