Philanthotoxin-7,4. Selective Antagonist of Various AMPA Receptors
Philanthotoxin-7,4 (PhTx-74) is a synthetic polyamine analogue of the naturally occurring wasp venom toxin philanthotoxin-4,3,3. It is a potent and selective antagonist of certain isoforms of the AMPA type of ionotropic glutamate receptors.
PhTx-74 inhibited GluR1 and GluR3 homomers as well as GluR1/GluR2 where 100 μM inhibited nearly 100% of the glutamate evoked currents. However, up to 500 μM had no or little effect on GluR2 or GluR2/GluR3 channels.
PhTx-74 (5 μM) was used as a tool to demonstrate circadian changes in AMPAR subtypes functionally expressed in somatosensory cortex slices and the removal of some AMPAR during sleep. Indeed, EPSPs were significantly depressed by PhTx-74 only after dark episodes. As a measure for changes in AMPAR subunit composition after cocaine administration, PhTx-74 was used in synaptic transmission evaluation.
AMPAR EPSCs from neurons treated earlier with cocaine showed increased sensitivity to bath application of 100 μM PhTx-74 compared with vehicle-treated cells, suggesting an increased contribution of GluR1-containing AMPARs to synaptic transmission after cocaine. PhTx-74 was used to evaluate the effects of transmembrane AMPAR regulatory proteins (TARPs) on AMPAR conductance; 100 μM PHTx-74 blocked GluA2/A4 currents to a different degree depending on the auxiliary TARP present.
Ion Channel Modulators; AMPA Receptor Blockers.
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