Neuromedin U can exert colon‐specific, enteric nerve‐mediated prokinetic activity, via a pathway involving NMU 1 receptor activation

Background and purpose: The neuromedin U (NMU) receptors, NMU 1 and NMU 2 , are expressed in the gut but their functions are unclear. This study explores the role of NMU in gastrointestinal motility. Experimental approach: The effects of NMU were examined in the forestomach and colon isolated from NMU 2 R wild‐type and NMU 2 R‐/‐ (knockout) mice, looking for changes in muscle tension and in nerve‐mediated responses evoked by electrical field stimulation (EFS), and in models of peristalsis in mouse colon and faecal pellet transit in guinea‐pig colon. Key results: In the mouse forestomach, NMU (1 nM‐10 μM) concentration‐dependently induced muscle contraction, in the presence of tetrodotoxin and atropine, in preparations from both wild‐type and NMU 2 R‐/‐ mice ( p EC 50 : 7.9, 7.6, E max : 0.26, 0.20g tension, respectively, n =8 each concentration). The same concentrations of NMU had no consistent effects on the responses to EFS ( n =8). In the mouse colon, NMU (0.1 nM‐1 μM) had no significant effect on baseline muscle tension ( n =8), but concentration‐dependently potentiated EFS‐evoked contractions in preparations from both wild‐type and NMU 2 R‐/‐ mice, p EC 50 : 8.1, 7.8, E max : 24%, 21%, respectively, n =6‐11. NMU (0.01 nM‐0.1 μM, n =5‐7) concentration‐dependently decreased the interval between waves of peristalsis in the mouse colon ( p EC 50 : 8.8) and increased the rate at which a faecal pellet moved along the guinea‐pig colon. Conclusions and implications: These results demonstrate that NMU exerts colon‐specific, nerve‐mediated, prokinetic activity, via a pathway involving activation of NMU 1 receptors. This suggests that this receptor may represent a molecular target for the treatment of intestinal motility disorders. British Journal of Pharmacology (2007) 150 , 502–508. doi: 10.1038/sj.bjp.0707004