PPADS tetrasodium salt

Purinergic receptor antagonist: PPADS is a non-selective P2 purinergic receptor antagonist, meaning it blocks various P2X and P2Y receptors. 

Mechanism / functional role

• It blocks recombinant P2X₁, P2X₂, P2X₃, P2X₅ with IC₅₀ in the range ~1–2.6 µM. 

• It also has activity against P2Y receptor subtypes: native P2Y₂-like (IC₅₀ ~ 0.9 mM) and recombinant P2Y₄ (IC₅₀ ~ 15 mM). 

• It can delay onset of calcium (Ca²⁺) responses under mild hypoosmotic stress in cortical slices, presumably by blocking P2 receptor–mediated ATP signaling.

• There is evidence it also blocks P2X₇ in certain contexts and has been used in vivo (e.g. in graft-versus-host disease models). 

• It is considered to not have appreciable activity at α₁-adrenergic, muscarinic (M₂, M₃), histamine H₁, or adenosine A₁ receptor types—i.e. it is relatively selective for purinergic (P2) systems over those other receptor classes. Wikipedia+4ScienceDirect+4

Uses and applications (in research)

• As a pharmacological tool in neuroscience, physiology, and cell signaling work to block extracellular ATP / ADP signaling mediated via P2 receptors.

• To test or dissect the role of P2X / P2Y receptors in e.g. ion flux, calcium signaling, neurotransmission, vascular responses, etc.

• In tissue slice experiments (e.g. brain slices) to inhibit ATP-mediated calcium responses.

• In vivo or ex vivo disease models where purinergic signaling is implicated (e.g. blocking P2X₇ in graft-versus-host disease models)