Evans Blue tetrasodium salt

IC50: 220 and 150 nM for GluRl and GIuR6, respectively.

Evans Blue tetrasodium salt is a potent inhibitor of AMPA and kainate receptor-mediated currents (GluRl and GIuR6).

Pharmacologically, the glutamate transporter is specific for glutamate and the closely related analogue L-aspartate does not block the uptake, whereas agents like L-homocysteate and La- aminoadipate block the vesicular L-glutamate uptake poorly.

In vitro: Evans blue inhibits the kainate-mediated responses of the non-NMDA receptor subunits (GIuRl, G1uR1,2, G1uRl,3, and G1uR2,3) expressed in Xenopus oocytes without the response of GluR3 and G1uR6 at low concentrations (IC50= 355 nM for the subunit combination GluR1,2). This pocess was partially reversible without competing with kainate for the agonist binding site [1]. In whole-cell patch clamp recordings of transfected human embryonic kidney 293 cells, Evans blue is a potent inhibitor of glutamate-evoked currents mediated by the kainate-type receptor GIuR6 as long as the AMPA-type receptor GluRl. Interestingly, pretreating with the lectin concanavalin cells recorded relatively little EB inhibition of GIuR6 currents, eliminating kainate receptor desensitization. In addition to decreasing GluR6-mediated peak current amplitude, EB significantly changed receptor desensitization by slowing the rate of onset by ~2-fold (1 M EB) and the rate of recovery by ~2-fold (0.1 p.M EB), and enhancing the steady state to peak current amplitude ratio by ~50-fold (1 M EB) [2].

In vivo: So far, no study in vivo has been conducted.

Clinical trial: So far, no clinical study has been conducted.

References:
[1] Roseth S, Fykse EM, Fonnum F.  Uptake of L-glutamate into rat brain synaptic vesicles: effect of inhibitors that bind specifically to the glutamate transporter. J Neurochem. 1995 Jul;65(1):96-103.
[2] Price CJ, Raymond LA.  Evans blue antagonizes both alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate and kainate receptors and modulates receptor desensitization. Mol Pharmacol. 1996 Dec; 50 (6):1665-71.