Salicylidene salicylhydrazide, a selective inhibitor ofβ1‐containing GABA_Areceptors

Abstract

1 A high-throughput assay utilizing the voltage/ion probe reader (VIPR) technology identified salicylidene salicylhydrazide (SCS) as being a potent selective inhibitor of a2b1g1y GABA A receptors with a maximum inhibition of 5675% and an IC 50 of 32 (23, 45) nM. 2 Evaluation of this compound using patch-clamp electrophysiological techniques demonstrated that the compound behaved in a manner selective for receptors containing the b1 subunit (e.g. maximum inhibition of 68.172.7% and IC 50 value of 5.3 (4.4, 6.5) nM on a2b1g1 receptors). The presence of a b1 subunit was paramount for the inhibition with changes between a1 and a2, g1 and g2, and the presence of a y subunit having little effect. 3 On all subtypes, SCS produced incomplete inhibition with the greatest level of inhibition at a1b1g1y receptors (74.371.4%). SCS displayed no use or voltage dependence, suggesting that it does not bind within the channel region. Concentration -response curves to GABA in the presence of SCS revealed a reduction in the maximum response with no change in the EC 50 or Hill coefficient. In addition, SCS inhibited pentobarbitone-induced currents. 4 Threonine 255, located within transmembrane domain (TM) 1, and isoleucine 308, located extracellularly just prior to TM3, were required for inhibition by SCS. 5 SCS did not compete with the known allosteric modulators, picrotoxin, pregnenolone sulphate, dehydroepiandrosterone 3-sulphate, bicuculline, loreclezole or mefenamic acid. Neither was the inhibition by SCS influenced by the benzodiazepine site antagonist flumazenil. 6 In conclusion, SCS is unique in selectively inhibiting GABA A receptors containing the b1 subunit via an allosteric mechanism. The importance of threonine 255 and isoleucine 308 within the b1 subunit and the lack of interaction with a range of GABA A receptor modulators suggests that SCS is interacting at a previously unidentified site.

α4βδ GABA A receptors are high-affinity targets for γ-hydroxybutyric acid (GHB)

“…The markedly higher GHB sensitivity at β1-containing vs. β(2/3)-containing α4δ GABA A receptors makes analogs designed specifically for the high-affinity GHB binding site (27,34) interesting as pharmacological tools for studying β1-containing receptors. To date, only few such compounds have been reported (35,36). The preference for β1 may, in part, explain the sleepmediating effects of GHB, because the endogenous pathway of sleep has been shown to depend mainly on β1-containing GABA A receptors, whereas anesthesia and hypnosis are mediated through β3-containing receptors (37,38).…”

GABAA receptor subunit β1 is involved in the formation of protease‐resistant prion protein in prion‐infected neuroblastoma cells

“…Salicylidene salicylhydrazide is a selective inhibitor of b1 subunit-containing GABAA receptors [19]. Treatment of ScN2a cells with this compound inhibited PrPres formation dose-dependently with a 50% inhibition dose of 450 nM (Fig.…”

Design, synthesis and biological evaluation of thiosemicarbazones, hydrazinobenzothiazoles and arylhydrazones as anticancer agents with a potential to overcome multidrug resistance

“…The free ligands and their Ni(II) [96], Cu(II), Ru(II) and Zn(II) [92,94,95] complexes were reported to possess antibacterial and antifungal activity. N4-phenylsalicylidene TSC (3a) has also been reported to show antitumor activity [95,97], GABA A receptor inhibition [98] and a very weak inhibition of RR [99]. Similarly, the acetaniline TSC (2p) forms Cu(II) complexes with moderate antibacterial and antifungal activity [46].…”