Cross-talk between 5-Hydroxytryptamine Receptors in a Serotonergic Cell Line

Abstract

The study of signaling cascades and of functional in- teractions between 5-hydroxytryptamine (5-HT) recep- tor pathways with heterogenous brain cell populations remains an arduous task. We took advantage of a sero- tonergic cell line to elucidate cross-talks between 5-HT receptors and to demonstrate the involvement of two 5-HT2 receptor subtypes in the regulation of 5-HT1B/1D function. The inducible 1C11 cell line has the unique property of acquiring within 4 days a complete seroton- ergic phenotype (1C11* cells), including three 5-HT re- ceptors. 5-HT1B/1D and 5-HT2B receptors are expressed since day 2 of the serotonergic differentiation while 5-HT2A receptors are induced at day 4. We first estab- lished that 5-HT2B receptors are coupled with the phos- pholipase A2 (PLA2)-mediated release of arachidonic acid (AA) and that the activation of 5-HT2B receptors in 1C11*d2 cells inhibits the 5-HT1B/1D receptor function via a cyclooxygenase-dependent AA metabolite. At day 4, this 5-HT2B-mediated inhibition of the 5-HT1B/1D func- tion can be blocked upon concomitant 5-HT2A activa- tion although a 5-HT2A/PLA2 positive coupling was ev- idenced. This suggests the existence in 1C11*d4 cells of pathway(s) for 5-HT2A receptors, distinct from PLC and PLA2. Finally, this study reveals the antagonistic roles of 5-HT2A and 5-HT2B receptors in regulating the func- tion of 5-HT1B/1D, a receptor involved in neuropsychi- atric disorders and migraine pathogenesis