We studied the effect of serrotonin on the osteoclastic differenciation. To assess the functional role of different 5-HT receptors in osteoclastogenesis, we used sevral agonists and antagonists whose Ketanserin which showed a significant effect at a concentration of 25 nM. For a first test, you can try this concentration.
Decreased osteoclastogenesis in serotonin-deficient mice
Y Chabbi-Achengli, AE Coudert, J Callebert, V Geoffroy, F Côté, C Collet, ...
Proceedings of the National Academy of Sciences 109 (7), 2567-2572