- Alomone Labs PhTx-74 inhibits AMPA Receptor 1 (GluR1) expressed in Xenopus oocytes.Currents were recorded following stimulation with 10 µM glutamate (bar on top) at -100 mV holding potential. Reversible inhibitory effects of 0.1 to 10 µM of PhTx-74 (#P-120) are demonstrated, as indicated by the bars at the bottom.
PhTx-74 (Philanthotoxin-7,4) 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 receptors1.
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 channels1-2.
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 episodes3. 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 cocaine4.
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 present5.
PhTx-74 (#P-120) is a highly pure, synthetic, and biologically active compound.