ly-392098 and cyclothiazide

The present study describes the activity of two novel potent and selective AMPA receptor potentiator molecules LY392098 and LY404187. LY392098 and LY404187 enhance glutamate (100 microM) stimulated ion influx through recombinant homomeric human AMPA receptor ion channels, GluR1-4, with estimated EC(50) values of 1.77 microM (GluR1(i)), 0.22 microM (GluR2(i)), 0.56 microM (GluR2(o)), 1.89 microM (GluR3(i)) and 0.20 microM (GluR4(i)) for LY392098 and EC(50) values of 5.65 microM (GluR1(i)), 0.15 microM (GluR2(i)), 1.44 microM (GluR2(o)), 1.66 microM (GluR3(i)) and 0.21 microM (GluR4(i)) for LY404187. Neither compound affected ion influx in untransfected HEK293 cells or GluR transfected cells in the absence of glutamate. Both compounds were selective for activity at AMPA receptors, with no activity at human recombinant kainate receptors. Electrophysiological recordings demonstrated that glutamate (1 mM)-evoked inward currents in human GluR4 transfected HEK293 cells were potentiated by LY392098 and LY404187 at low concentrations (3-10 nM). In addition, both compounds removed glutamate-dependent desensitization of recombinant GluR4 AMPA receptors. These studies demonstrate that LY392098 and LY404187 allosterically potentiate responses mediated by human AMPA receptor ion channels expressed in HEK 293 cells in vitro.

Topics: Allosteric Regulation; Antihypertensive Agents; Benzothiadiazines; Calcium; Cell Line; Dioxoles; Dose-Response Relationship, Drug; Drug Synergism; Electrophysiology; Excitatory Amino Acid Agonists; Humans; Piperidines; Receptors, AMPA; Receptors, Glutamate; Recombinant Proteins; Sulfonamides; Thiophenes

The present study describes the pharmacological activity of two novel positive allosteric modulators at AMPA receptors in acutely isolated rat cerebellar Purkinje neurons and cultured rat hippocampal neurons. Currents elicited by application of glutamate (100 microM) to isolated cerebellar Purkinje neurons were potentiated by LY392098, LY404187, cyclothiazide, CX516 and aniracetam. The rank order of potency was LY404187> LY392098> cyclothiazide > CX516> aniracetam. LY392098 displayed a higher maximal efficacy than the other compounds examined. AMPA-activated inward currents in cultured rat hippocampal neurons were potentiated by LY392098, LY404187 and cyclothiazide in a reversible and concentration-dependent manner although considerable heterogeneity in the magnitude of response from cell to cell was observed. LY392098 was ineffective in potentiating AMPA receptor responses when dialyzed via the intracellular solution. The selectivity profiles of the two novel AMPA receptor potentiators were examined. LY392098 or LY404187 had minimal activity on NMDA receptor responses, on voltage-gated calcium channel currents in cultured hippocampal neurons and on GluR5 kainate receptor currents in acutely isolated rat dorsal root ganglion neurons.

Topics: Allosteric Regulation; Animals; Antihypertensive Agents; Benzothiadiazines; Cells, Cultured; Drug Synergism; Excitatory Amino Acid Agonists; Hippocampus; Neurons; Purkinje Cells; Rats; Receptors, AMPA; Receptors, Kainic Acid; Sulfonamides; Thiophenes

The present experiments investigated the ability of LY392098, a novel positive allosteric modulator of AMPA receptors, to potentiate AMPA receptor-mediated currents of neurons in the prefrontal cortex (PFC). Co-application of LY392098 (0.03-10 microM) with AMPA (5 microM) enhanced current through AMPA receptor/channels in acutely isolated PFC neurons in a concentration-dependent manner. Estimates of the potency (EC(50)) and efficacy for LY392098 yielded an EC(50) value of 1.7+/-0.5 microM and a maximal potentiation of a 31.0+/-4.1-fold increase relative to current evoked by AMPA alone. The potentiation was activity-dependent, becoming evident only in the presence of agonist, and time-dependent, continuously developing over prolonged application times. An extracellular site of action was inferred by the absence of potentiation when the compound was applied intracellularly. LY392098 also increased the potency of agonist for the receptor by approximately sevenfold. Selectivity assays showed that the effects of LY392098 were exclusive for AMPA receptors, having no activity at N-methyl-D-aspartate (NMDA) receptors in PFC neurons. Extracellular recordings from single PFC neurons in vivo showed that administration of LY392098 (0.001-10 microg/kg, i.v.) enhanced the probability of evoked action potential discharge in response to stimulation of glutamatergic afferents from the ventral subiculum of the hippocampal formation. Spontaneous activity of PFC neurons was also increased. Collectively, these results demonstrate that LY392098 is a highly potent, selective and centrally active positive modulator of native AMPA receptors.

Topics: Action Potentials; Animals; Benzothiadiazines; Diuretics; Dose-Response Relationship, Drug; Drug Synergism; Excitatory Amino Acid Agonists; Male; Neurons; Prefrontal Cortex; Pyrrolidinones; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Sodium Chloride Symporter Inhibitors; Sulfonamides; Thiophenes