THE MOUSE 5-HT2B RECEPTOR - POSSIBLE INVOLVEMENT IN TROPHIC FUNCTIONSOF SEROTONIN

The novel serotonin receptor 5-HT2B shows the highest homology to the 5-HT2 family of receptors. The pharmacological profile of membranes fr om 5-HT2B cDNA stably transfected LMTK- cell line, corresponds to a ne w 5-HT2-like receptor named 5-HT2B, although some difference exists be tween the mouse and rat pharmacology. A similar pharmacological profil e is detected on the immortalized teratocarcinoma-derived cell line 1C 11 upon 2 days of serotoninergic differenciation by cAMP. In both cell lines, the analysis I-125-DOI binding reveals the presence of a singl e class of sites, the affinity of which is one order of magnitude lowe r than the one reported for the 5-HT2A receptor. This demonstrates tha t the 5-HT2B receptor is functionnally expressed before the complete s erotoninergic differenciation of 1C11 cells. These observations are in good agreement with the presence of 5-HT2B mRNA in early mouse embryo nic development. Furthermore, the major sites of 5-HT2B mRNA embryonic expression are in the heart, and in the neural fold before the closur e of the neural tube. Therefore, this receptor could account at least in part for the trophic functions attributed to the 5-HT2-like recepto rs.