EC50 or pD2 values for ACh, Histamine and MCh - Where to find a standard value?? (Apr/16/2010 )

These EC50 or pD2 values change in every reaction i read but I have been asked to get this(and reference it!) and compare it with the ones I got from semi log graph from my experiment.

Now, where do I look to find Standard pD2 values for the following?? so i can compare them with mine.

Acetylcholine pD2 = ?
Metahcholine pD2= ?
Histamine pD2 = ?


By the way,
mine were:
ACh pD2= 6.69
MCh pD2= 6.60
His pD2= 6.79

EC50 is no K (constant), so it depends on experimental conditions