The mouse 5-HT2B receptor: possible involvement in trophic functions of serotonin.

The novel serotonin receptor 5-HT2B shows the highest homology to the 5-HT2 family of receptors. The pharmacological profile of membranes from 5-HT2B cDNA stably transfected LMTK- cell line, corresponds to a new 5-HT2-like receptor named 5-HT2B, although some difference exists between the mouse and rat pharmacology. A similar pharmacological profile is detected on the immortalized teratocarcinoma-derived cell line 1C11 upon 2 days of serotoninergic differenciation by cAMP. In both cell lines, the analysis 125I-DOI binding reveals the presence of a single class of sites, the affinity of which is one order of magnitude lower than the one reported for the 5-HT2A receptor. This demonstrates that the 5-HT2B receptor is functionally expressed before the complete serotoninergic differentiation of 1C11 cells. These observations are in good agreement with the presence of 5-HT2B mRNA in early mouse embryonic development. Furthermore, the major sites of 5-HT2B mRNA embryonic expression are in the heart, and in the neural fold before the closure of the neural tube. Therefore, this receptor could account at least in part for the trophic functions attributed to the 5-HT2-like receptors.