Expression of the tachykinin receptor mRNAs in healthy human colon

Tachykinins are a family of neuropeptides, involved in a variety of physiological and pathological processes occurring in the gastrointestinal tract. They act via three distinct types of receptors, tachykinin NK1, NK2, and NK3 receptors, which belong to the family of G protein-coupled receptors. The aim of the present study was to characterize, for the first time in the healthy human colon, the TACR1, TACR2 and TACR3 mRNAs encoding the three different tachykinin receptors and to measure their relative expression by quantitative reverse transcription-PCR assay. Our results confirm the broad distribution of the tachykinin receptors but evidenced significant differences in the expression level of their respective mRNAs. A higher expression level of the TACR2 mRNA alpha isoform, the gene encoding the functional tachykinin NK2 receptor, was observed in comparison to TACR1 and TACR3 mRNAs genes encoding for NK1 and NK3 receptors respectively. The prevalence of the TACR2 mRNA alpha isoform strongly suggests a major involvement of tachykinin NK2 receptor in the regulation of human colonic functions.