Structural requirements for novel willardiine derivatives acting as AMPA and kainate receptor antagonists

Abstract

1 The natural product willardiine is an AMPA receptor agonist. We have examined the structural changes required to convert willardiine into an antagonist at AMPA and kainate receptors. Structureactivity analysis has been carried out to discover the structural features required to increase the potency and/or selectivity of the antagonists at AMPA or kainate receptors. 2 Reduction of the fast component of the dorsal root-evoked ventral root potential (fDR-VRP) has been used to investigate AMPA receptor antagonist activity. To examine antagonist activity at kainate receptors, the ability of compounds to depress kainate-induced depolarisations of dorsal root fibres was assessed. 3 Blocking ionisation of the uracil ring by adding a methyl group to the N 3 position was not sufficient to convert willardiine into an antagonist. However, willardiine derivatives with a side-chain bearing a carboxylic acid group at the N 3 -position of the uracil ring could antagonise AMPA and kainate receptors. 4 S stereochemistry was optimal for antagonism. When compounds with differing interacidic group chain lengths were compared, a group chain length of two methylene groups was preferable for AMPA receptor antagonism in the series of compounds bearing a carboxyalkyl side chain (UBP275, UBP277 and UBP279 reduced the fDR-VRP with IC 50 values of 287741, 23.873.9 and 136717 mm, respectively). For kainate receptor antagonism, two or three methylene groups were almost equally acceptable (UBP277 and UBP279 reduced dorsal root kainate responses with apparent K D values of 73.174.5 and 60.574.1 mm, respectively). 5 Adding an iodo group to the 5-position of UBP277 and UBP282 enhanced activity at kainate receptors (UBP291 and UBP301 antagonised kainate responses on the dorsal root with apparent K D values of 9.8371.62 and 5.9470.63 mm, respectively). 6 The most useful antagonist identified in this study was UBP301, which was a potent and B30-fold selective kainate receptor antagonist. UBP282 may also be of use in isolating a non-GluR5-mediated kainate response.

Mechanism of AMPA Receptor Activation by Partial Agonists

“…On the other hand, the binding of UBP282 results in hyperextension of the lobes due to rather bulky groups that interact specifically with sites on both lobes (39). Although this compound has a relatively low affinity, it is clearly an antagonist (40). The 1 H, 15 N-HSQC spectra were unchanged in the presence and absence of reducing agents, suggesting that the A452C/S652C disulfide did not form.…”

“…UBP282 is a bulky willardiine derivative that produces lobe extension (i.e. lobe opening greater than the apo form; 39) and functions as a relatively low affinity antagonist of GluA2 (40). The 1 H-15 N HSQC NMR spectra of Cu-phenantroline-oxidized and DTTreduced GluA2 LBD in the presence of UBP282 are shown in Fig.…”

Metabotropic glutamate receptor activity induces a novel oscillatory pattern in neonatal rat hypoglossal motoneurones

“…4 (see asterisks). In this cell that developed standard oscillations in the presence of 25 µm DHPG, we set the membrane potential at +40 mV and applied a combination of selective blockers for kainate receptors (10 µm UBP 301; More et al 2003), NMDA receptors (50 µm APV) and GABA B receptors (10 µm CGP 55845; Towers et al 2002) which did not block the generation of such slow, irregular outward currents (Fig. 4A).…”

Mechanism of Action of Low Dose Preparations from <i>Coffea arabica</i>, <i>Gelsemium</i> and <i>Veratrum</i> Based on <i>in Vivo</i> and <i>in Vitro</i> Neurophysiological Findings

“…For antagonization of the stimulus-induced physiological effect at NMDA, AMPA, Kainate and metabotropic glutamate receptors the following chemicals were used respectively: CGS 19755 [24], NBQX [25], UB 301 [26], and RS-APICA [27]. All chemicals were from BIOTREND Chemikalien GmbH, Cologne, Germany.…”