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Comparison of 5-HT4 and 5-HT7 receptor expression and function in the circular muscle of the human colon


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Irving, HR, Tan, YY, Tochon-Danguy, N, Liu, H, Chetty, N, Desmond, PV, Pouton, CW and Coupar, IM 2007 , 'Comparison of 5-HT4 and 5-HT7 receptor expression and function in the circular muscle of the human colon' , Life Sciences, vol. 80, no. 13 , pp. 1198-1205 , doi: 10.1016/j.lfs.2006.12.025.

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Serotonin receptors are potential targets for treating functional bowel disorders. This study investigated the functional roles and expression of the 5-HT4 and the 5-HT7 receptor, which coexist in human colon circular smooth muscle. 5-HT3 receptor expression was also investigated. Part of the relaxant response to 5-HT was due to activation of 5-HT4 receptors as the apparent pKB value of the selective 5-HT4 antagonist, GR 113808, was 9.36. 5-HT4 mRNA levels were low in five tissues and undetectable in four others, but all responded to 5-HT with an EC50 value of 102.54 ± 19.32 nM. The contribution of 5-HT7 receptors to the response was not readily demonstrated using the selective 5-HT7 antagonist, SB-269970, as its apparent pKB value of 7.19 (5-HT4 block with 1 μM GR 113808) was lower than the value obtained using the 5-HT7 guinea pig ileum assay (8.62). Nevertheless, the 5-HT7 receptor was expressed more consistently than the 5-HT4, but at similar levels. The 5-HT3Ashort and 5-HT3B subunits were co-expressed at similar levels, but the 5-HT3Along subunit was detected in only five of the nine samples tested. The findings show that 5-HT4-induced relaxation occurs at low to undetectable levels of tissue mRNA, as measured by qPCR. Although 5-HT7 receptor mRNA is detected at low, but consistent levels, the functional activity of this receptor is not readily identified given the currently available drugs.

Item Type: Article
Authors/Creators:Irving, HR and Tan, YY and Tochon-Danguy, N and Liu, H and Chetty, N and Desmond, PV and Pouton, CW and Coupar, IM
Keywords: Serotonin receptors; 5-HT3 receptors; 5-HT4 receptors; 5-HT7 receptors; Gastrointestinal tract; Human tissue; Colonic smooth muscle
Journal or Publication Title: Life Sciences
Publisher: Pergamon-Elsevier Science Ltd
ISSN: 0024-3205
DOI / ID Number: 10.1016/j.lfs.2006.12.025
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