Mu-opioid receptor ligands lack receptor subtype selectivity in the aequorin luminescence-based calcium assay4393, Fichna, J., Staniszewska R., Poels J, J. Broeck Vanden, and Janecka A.E. , Chem.Biol.Drug Des, 0/9/2007, Volume 70, Issue 3, Number 253, p.247 - 253, (2007)