PPADS (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid) is a selective purinergic P2X
antagonist
An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain.ATP or α,β,methylene-ATP. It appears to be relatively selective for P2X receptors, having no appreciable activity at α1 adrenergic, muscarinic M2 and M3, histamine H1, and adenosine A1 receptors.