Binding assays in osteoblast primary cultures were carried out at plating (day 0) and after 7, 10, 13 and 21 days. 5-HT1A (A), 5-HT2A (B), and 5-HT2B (C) binding sites were determined in WT (black bars) and in 5HT2BR−/− osteoblastic cells (open bars). *, significant difference from WT at p<0.001. $, significant difference from day 0 at p<0.01. $$, significant difference from day 0 at p<0.001.