Sequential onset of three 5-HT receptors during the 5-hydroxytryptaminergic differentiation of the murine 1C11 cell line.

1. The murine 1C11 clone, which derives from a multipotential embryonal carcinoma cell line, has the features of a neuroectodermal precursor. When cultured in the presence of dibutyryl cyclic AMP, the 1C11 cells extend bipolar extensions and express neurone-associated markers. After 4 days, the resulting cells have acquired the ability to synthesize, take up, store and catabolize 5-hydroxytryptamine (5-HT). We have thus investigated the presence of 5-HT receptors during the 5-hydroxytryptaminergic differentiation of this inducible 1C11 cell line. 2. As shown by the binding of [125I]-GTI and the CGS 12066-dependent inhibition of the forskolin-induced cyclic AMP production, functional 5-HT1B/1D receptors become expressed on day 2 of 1C11 cell differentiation. The density of these receptors remained unchanged until day 4. 3. The same holds true for the 5-HT2B receptor, also identified by its pharmacological profile and its positive coupling to the phosphoinositide cascade. 4. On day 4 of 1C11 cell differentiation, a third 5-HT receptor, pharmacologically and functionally similar to 5-HT2A, had become induced. 5. Strikingly, the amounts of each transcript encoding 5-HT1B, 5-HT2A and 5-HT2B receptor did not very significantly during the time course of the 1C11 5-hydroxytryptaminergic differentiation. 6. The clone 1C11 may thus provide a useful in vitro model for studying regulation(s) between multiple G-linked receptors as well as the possible role of 5-HT upon the expression of a complete 5-hydroxytryptamine phenotype.