Nociceptin effect on intestinal motility depends on opioid-receptor like-1 receptors and nitric oxide synthase co-localization

Aim: To study the effect of the opioid-receptor like-1 (ORL1) agonist nociceptin on gastrointestinal (GI) myenteric neurotransmission and motility.

Methods: Reverse transcriptase - polymerase chain reaction and immunohistochemistry were used to localize nociceptin and ORL1 in mouse tissues. Intracellular electrophysiological recordings of excitatory and inhibitory junction potentials (EJP, IJP) were made in a chambered organ bath. Intestinal motility was measured in vivo.

Results: Nociceptin accelerated whole and upper GI transit, but slowed colonic expulsion in vivo in an ORL1-dependent manner, as shown using [Nphe(1)]NOC and AS ODN pretreatment. ORL1 and nociceptin immunoreactivity were found on enteric neurons. Nociceptin reduced the EJP and the nitric oxide-sensitive slow IJP in an ORL1-dependent manner, whereas the fast IJP was unchanged. Nociceptin further reduced the spatial spreading of the EJP up to 2 cm.

Conclusion: Compounds acting at ORL1 are good candidates for the future treatment of disorders associated with increased colonic transit, such as diarrhea or diarrhea-predominant irritable bowel syndrome.