PubMed Health⌕ Search

Biomedical subjects

D Lodge

Publications and source records attributed to D Lodge.

At least 55 records · Page 3Linked to original sources
PubMed1996

Activity of 2,3-benzodiazepines at native rat and recombinant human glutamate receptors in vitro: stereospecificity and selectivity profiles.

The activity and selectivity of the glutamate receptor antagonists belonging to the 2,3-benzodiazepine class of compounds have been examined at recombinant human non-NMDA glutamate receptors expressed in HEK293 cells and on native rat NMDA and non-NMDA receptors in vitro. The racemic 2,3-benzodiazepines GYKI52466, LY293606 (GYKI53405) and LY300168 (GYKI53655) inhibited AMPA (10 microM)-mediated responses in recombinant human GluR1 receptors expressed in HEK293 cells with approximate IC50 values of 18 microM, 24 microM and 6 microM, respectively and AMPA (10 microM) responses in recombinant human GluR4 expressing HEK293 cells with approximate IC50 values of 22 microM, 28 microM and 5 microM, respectively. GYKI 52466, LY293606 and LY300168 were non-competitive antagonists of AMPA receptor-mediated responses in acutely isolated rat cerebellar Purkinje neurons with approximate IC50 values of 10 microM, 8 microM and 1.5 microM, respectively. The activity of racemic compounds LY293606 and LY300168 was established to reside in the (-) isomer of each compound. At a concentration of 100 microM, GYKI52466, LY293606 and LY300168 produced < 30% inhibition of kainate-activated currents evoked in HEK293 cells expressing either human homomeric GluR5 or GluR6 receptors or heteromeric GluR6+KA2 kainate receptors. The activity of the 2,3-benzodiazepines at 100 microM was weak at kainate receptors, but was stereoselective. Similar levels of inhibition were observed for kainate-induced currents in dorsal root ganglion neurons. Intact tissue preparations were also used to examine the stereoselective actions of the 2,3-benzodiazepines. In the cortical wedge preparation, the active isomer of LY300168, LY303070, produced a non-competitive antagonism of AMPA-evoked depolarizations with smaller changes in depolarizations induced by kainate and no effect on NMDA-dependent depolarizations. LY303070 was also effective in preventing 30 microM AMPA-induced depolarizations in isolated spinal cord dorsal roots with an approximate IC50 value of 1 microM. Synaptic transmission in the hemisected spinal cord preparation was stereoselectively antagonized by the active isomers of LY300168 and LY293606. In summary, these results indicate that 2,3-benzodiazepines are potent, selective and stereospecific antagonists of the AMPA subtype of the non-NMDA glutamate receptor.

Animals↗
PubMed1995

(3SR,4aRS,6SR,8aRS)-6-(1H-tetrazol-5-yl)decahydroisoquinoline-3-carboxylic acid, a novel, competitive, systemically active NMDA and AMPA receptor antagonist.

We report the synthesis and characterization of 6 (LY246492), which is a competitive N-methyl-D-aspartate (NMDA) and 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propanoic acid (AMPA) receptor antagonist. Tetrazole-substituted amino acid 6 was prepared in four steps from the recently described aldehyde 7. The optical isomers (-)-6 and (+)-6 were obtained from the same sequence of reactions using the corresponding isomers of 7. The compound displaces both NMDA and AMPA receptor binding and antagonizes depolarizations in cortical slices evoked by both NMDA and AMPA. In mice and pigeons, the compound showed antagonism of responses mediated through NMDA and AMPA receptors. Using the resolved optical isomers of 6, both NMDA and AMPA antagonist activities were found to reside in a single isomer, (-)-6.

Animals↗
PubMed1995

Pharmacology of metabotropic glutamate receptor-mediated enhancement of responses to excitatory and inhibitory amino acids on rat spinal neurones in vivo.

Using the technique of microelectrophoresis on spinal neurones in pentobarbitone-anaesthetized rats, (1S,3R)-1-aminocyclo-pentane-1,3-dicarboxylate (1S,3R-ACPD) reversibly and dose-dependently enhanced responses to alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA), kainate, N-methyl-D-aspartate (NMDA) and L-glutamate to a similar extent. 1S,3R-ACPD also enhanced inhibitory responses to both glycine and gamma-aminobutyrate (GABA). Such results are consistent with a metabotropic glutamate receptor-mediated decrease in membrane conductance. 1S,3R-ACPD was the most active metabotropic agonist tested for these effects; the rank order of activity was: 1S,3R-ACPD > or = (2S,3S,4S)alpha-(carboxycyclopropyl)-glycine(L-CCG-l) > (R, S)-3,5-dihydroxy-phenylglycine (3,5-DHPG) > (S)-homoquisqualate > quisqualate = 1S,3S-ACPD > L-2-amino-4-phosphonobutyrate (L-AP4) > 1R,3S-ACPD. These effects of 1S,3R-ACPD were antagonized by (RS)-alpha-methyl-4-carboxy-phenylglycine (M4CPG) and (S)-4-carboxy-3-hydroxy-phenylglycine (4C3HPG) but not by (S)-4-carboxy-phenylglycine (4CPG) or L-amino-3-phosphono-propionate (L-AP3). The pharmacology of the actions of mGluR agonists and antagonists on rat spinal neurones in vivo does not obviously correlate with the published pharmacology of a single cloned metabotropic glutamate receptor subtype but rather suggests that both Group 1 and 2 receptors contribute to the above effects.

Amino Acids↗
PubMed1995

Pharmacological analysis of 4-carboxyphenylglycine derivatives: comparison of effects on mGluR1 alpha and mGluR5a subtypes.

The antagonist effects of the 4-carboxyphenylglycines: (S)-4-carboxy-3hydroxyphenylglycine (4C3HPG), (S)-4-carboxyphenylglycine (4CPG) and (+)-alpha-methyl-4-carboxyphenylglycine (M4CPG) were compared on functional responses of human metabotropic glutamate receptor (mGluR) subtypes mGluR1 alpha and mGluR5a. These receptors both belong to group 1 type mGluRs which couple to the phosphoinositide (PI) hydrolysis/[Ca2+]i mobilization signal transduction pathway and are closely related in both structure and agonist pharmacology. In this study, the IC50 values obtained for quisqualate induced PI hydrolysis responses show that although all the phenylglycines are antagonists for both mGluR1 alpha and mGluR5a, the compounds exhibit differential potencies at these receptor subtypes. The 4C3HPG derivative was the most potent antagonist for both mGluR1 alpha (IC50 range: 19-50 microM) and mGluR5a (IC50 range: 53-280 microM). 4CPG produced an IC50 range of 4r-72 microM for mGluR1 alpha and 150-156 microM for mGluR5a cells. The potency of the M4CPG could not be distinguished from that of 4CPG with IC50 ranges of 29-100 microM and 115-210 microM for mGluR1 alpha and mGluR5a respectively. Further characterization of the dose-response effects of the compounds on quisqualate induced [Ca2+]i mobilization showed that although the magnitude of phenylglycine inhibition was reduced for both mGluR subtypes compared to those observed for stimulation of PI hydrolysis (except for 4C3HPG on mGluR1 alpha), similar differences in the relative potencies of the phenylglycines between mGluR1 alpha (IC50s: 40 +/- 10 microM for 4C3HPG: 300-1000 microM for 4CPG and M4CPG) and mGluR5a (IC50s: > 1000 microM) were evident.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

In vitro and in vivo antagonism of AMPA receptor activation by (3S, 4aR, 6R, 8aR)-6-[2-(1(2)H-tetrazole-5-yl) ethyl] decahydroisoquinoline-3-carboxylic acid.

The in vitro and in vivo pharmacology of a structurally novel competitive antagonist for the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) subtype of excitatory amino acid receptors is described. LY215490, (+/-)(6-(2-(1-H-tetrazol-5-yl)ethyl) decahydroisoquinoline-3-carboxylic acid), was shown to displace selectively 3H-AMPA and 3H-6-cyano-7-nitro- quinoxaline-2,3-dione (3H-CNQX) binding to rat brain membranes. LY215490 potently antagonized quisqualate-and AMPA-induced depolarizations of rat cortical slices in a competitive manner, while requiring higher concentrations to antagonize the effects of N-methyl-D-aspartate (NMDA) and kainate. In slices of rat hippocampus, LY215490 also selectively antagonized AMPA-evoked release of 3H-norepinephrine. These AMPA receptor activities were due to the (-) isomer of the compound. (3S,4aR,6R, 8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl] decahydroisoquinoline-3-carboxylic acid (LY293558). LY215490 was centrally active following parenteral administration in mice as demonstrated by protection versus maximal electroshock seizures and decreases in spontaneous motor activity. LY215490 (its active isomer being LY293558) represents a novel pharmacological agent for in vitro and in vivo studies of AMPA receptor function in the CNS.

Animals↗
PubMed1995

Distribution of AMPA-selective glutamate receptor subunits in the human hippocampus and cerebellum.

The distribution of AMPA-selective subunits, GluR1-4, was determined in the human hippocampus and cerebellum by in situ hybridization and immunocytochemistry. In the hippocampus, in situ hybridization revealed that GluR1 and GluR2 mRNAs were similarly distributed and highly expressed in the dentate gyrus, with lower levels in the CA regions. GluR3 and GluR4 mRNAs were expressed at very low levels. Immunocytochemical studies showed that GluR1- and GluR2/3-immunoreactivity were highest in the dentate molecular and granular layers. In the CA regions, GluR1 and GluR2/3 staining was observed in pyramidal cell bodies and surrounding neuropil and was more intense in CA4/3/2 compared with CA1. GluR4-immunoreactivity was low throughout the hippocampus. In the cerebellum, GluR1 and GluR4 transcripts were expressed in the granular and Purkinje cell/Bergmann glia layers. GluR2 mRNA was highly expressed in the granular layer and individual Purkinje cells, while GluR3 mRNA was not detectable in the cerebellum. GluR1- and GluR4-immunoreactivity were localized to Purkinje cells and putative Bergmann glia, as well as their processes extending into the molecular layer. GluR2/3 staining was intense in Purkinje cells, with moderate staining in the granular layer. Thus, GluR1-4 subunits are differentially distributed in the hippocampus and cerebellum. In addition, the distribution of subunit mRNA and protein correlate well with each other and with the glutamatergic neuroanatomy of the hippocampus and cerebellum.

Aged↗
PubMed1994

The neuroprotective effects of the decahydroisoquinoline, LY 215490; a novel AMPA antagonist in focal ischaemia.

LY 215490 (3RS,4aRS,6RS,8aRS)-6-[2-(1(2)H-tetrazole-5- yl)ethyl]decahydroisoquinoline-3-carboxylic acid), a novel, selective, competitive and systemically active AMPA receptor antagonist was tested as a neuroprotective agent against focal ischaemia in a model of permanent MCA occlusion in the rat. LY 215490 was administered at a dose of 10, 30 or 100 mg/kg 30 min prior to and post-MCA occlusion. The animals were allowed to survive for 24 hr, following which time the brains were processed for volumetric analysis of the infarct size. The low dose of LY 215490 was not effective against the infarct volume in the hemisphere, cortex or caudate. The 2 x 30 mg/kg dose of LY 215490 resulted in 25 and 31% protection against the volume of hemispheric and cortical ischaemic damage, respectively. The highest dose of LY 215490 resulted in a reduced neuroprotective effect with 23 and 27% protection against the volume of hemispheric and cortical ischaemic damage, respectively. The slightly reduced neuroprotective effect of the highest dosing regimen may be due to the respiratory problems seen with this dose. Neither of the two neuroprotective doses of LY 215490 produced any reduction in the volume of caudate damage which represents the core of the infarct.

Analysis of Variance↗
PubMed1993

Cyclothiazide reverses AMPA receptor antagonism of the 2,3-benzodiazepine, GYKI 53655.

On rat cortical slices, cyclothiazide, 1-100 microM, (ED50 = 7.1 +/- 1.1 microM) enhanced the depolarizing action of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) but not that of N-methyl-D-aspartate (NMDA). Cyclothiazide 10 microM also reversed the action of a 2,3-benzodiazepine, GYKI 53655, which is a non-competitive AMPA receptor antagonist, but not that of the quinoxalinedione, NBQX, which is a competitive AMPA receptor antagonist.

Animals↗
PubMed1993

Pharmacological characterisation of the calcium channels coupled to the plateau phase of KCl-induced intracellular free Ca2+ elevation in chicken and rat synaptosomes.

The effect of various blockers of voltage operated calcium channels (VOCCs) was studied on the non-inactivating, plateau phase of KCl-induced intracellular free Ca2+ ([Ca2+]i) elevation in rat cortical and chicken forebrain synaptosomes. In chicken synaptosomes, omega-CgTx GVIA (0.1 nM to 1 microM) and omega-CgTx MVIIA (0.1 nM to 1 microM), both selective blockers of N-type Ca2+ channels, produced a concentration-dependent inhibition of the plateau phase of [Ca2+]i elevation. omega-CgTx GVIA (IC50 value 28 nM) was more potent than omega-CgTx MVIIA (IC50 value 78 nM), but at submaximal concentrations, took longer to reach its maximum effect (20 min for omega-CgTx GVIA; 10 min for omega-CgTx MVIIA). At 1 microM, the highest concentration tested, each toxin blocked > 85% of [Ca2+]i elevation. The effect of omega-CgTx GVIA on the extent and time-course of inhibition of [Ca2+]i elevation was maintained in a Na(+)-free, choline substituted, medium. omega-Aga IVA (300 nM), a selective blocker of P-type calcium channels, inhibited 28 +/- 5% of [Ca2+]i elevation. The effect of a combination of submaximal inhibitory concentrations of omega-CgTx GVIA (100 nM) and omega-Aga IVA (300 nM) was less than additive. In rat synaptosomes, omega-CgTx GVIA (1 microM) and omega-CgTx MVIIA (1 microM), blocked only 18 +/- 5% and 17 +/- 4% of the plateau phase of free Ca2+ elevation, respectively. omega-Aga IVA produced a concentration-dependent inhibition of [Ca2+]i elevation in this preparation. Threshold inhibition was observed at 1 nM, and maximum inhibition (64 +/- 8%) at 1 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Patch clamp studies on the kinetics and selectivity of N-methyl-D-aspartate receptor antagonism by memantine (1-amino-3,5-dimethyladamantan).

Memantine (1-amino-3,5-dimethyladamantan) was tested as an antagonist of N-methyl-D-aspartate (NMDA) receptors on cultured superior collicular and hippocampal neurones using the patch clamp technique and its actions were compared to those of Mg2+ ions, ketamine, dextrorphan, dextromethorphan, phencyclidine and dizocilpine (MK-801). Memantine (2-33 microM) concentration-dependently antagonized responses to NMDA 100 microM with an IC50 of 2.92 +/- 0.05 microM. In contrast, current responses to (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (L-AMPA 50-100 microM) and gamma-amino butyric acid (GABA 10 microM) were unaffected by Memantine 8 microM. Memantine 8 microM caused a non-parallel shift of the NMDA concentration-response curve to the right in a manner indicative of uncompetitive open channel block. The effects of memantine were similar to ketamine in that both antagonists were weakly use- and strongly voltage-dependent. In contrast, MK-801, phencyclidine and dextrorphan showed much slower kinetics that was reflected in their marked use- and weaker voltage-dependency. The antagonistic effects of memantine were not reversed by increasing concentrations of glycine (0.1-100 microM) ruling out the possibility of an interaction of memantine with the strychnine-insensitive glycine modulatory site associated with the NMDA receptor-channel complex. Memantine (1-100 microM) also selectively antagonized responses to NMDA (40 microM) in the cortical wedge preparation with IC50 of 12.9 +/- 1.5 microM.

Animals↗
PubMed1992

Methohexitone antagonises kainate and epileptiform activity in rat neocortical slices.

Using a grease-seal technique on cortical slices, methohexitone (10-316 microM) dose dependently and reversibly reduced depolarising responses to kainate more than those to alpha-amino-3-hydroxy-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate (NMDA). The respective pA2 values were 4.9 +/- 0.07, 3.6 +/- 0.03 and 4.0 +/- 0.05 whereas, for 6-nitro,7-sulphamoylbenz[F]quinoxalinedione (NBQX), they were 5.8 +/- 0.06, 6.7 +/- 0.05 and < 4.0. Methohexitone was also more effective than NBQX in reducing the spontaneous epileptiform activity occurring in these cortical slices. Thus 10 and 20 microM of this short-acting barbiturate reduced afterpotentials and burst frequencies respectively by about 50% whereas NBQX 10 microM only reduced burst frequency by some 15%. The results are discussed with respect to a putative methohexitone- and kainate-sensitive autoreceptor which facilitates presynaptic glutamate release.

Action Potentials↗
PubMed1992

6-substituted decahydroisoquinoline-3-carboxylic acids as potent and selective conformationally constrained NMDA receptor antagonists.

We have prepared a series of 6-substituted decahydroisoquinoline-3-carboxylic acids, and structurally similar analogs, as potential N-methyl-D-aspartate receptor antagonists. There is a large body of evidence to support the use of such compounds as cerebroprotective agents in a variety of acute and chronic neurodegenerative disorders, where some component of glutamate-mediated excitotoxicity may exist. The compounds prepared were evaluated in vitro in both receptor binding assays ([3H]CGS19755, [3H]AMPA, and [3H]kainic acid) and in a cortical wedge preparation (versus NMDA, AMPA, and kainic acid) to determine affinity, potency, and selectivity. The new amino acids were also evaluated in vivo for their ability to block NMDA-induced lethality in mice. We synthesized many of the possible diastereomers of the decahydroisoquinoline nucleus in order to examine the spatial and steric requirements for affinity at the NMDA receptor and activity as NMDA antagonists. From our structure-activity relationship we identified two potent and selective NMDA receptor antagonists, the phosphonate- and tetrazole-substituted amino acids 31a and 32a, respectively, that show good activity in animals following systemic administration. For example, 31a and 32a selectively displaced [3H]CGS19755 binding with IC50S of 55 +/- 14 and 856 +/- 136 nM, respectively, and selectively antagonized responses due to NMDA in a cortical wedge preparation with IC50S of 0.15 +/- 0.01 and 1.39 +/- 0.29 microM, respectively. And compounds 31a and 32a blocked NMDA-induced lethality in mice with minimum effective doses of 1.25 and 2.5 mg/kg (intraperitoneal), respectively. These novel amino acids are among some of the most potent NMDA antagonists described thus far, and are excellent candidates for development as neuroprotective agents for a number of CNS disorders.

Animals↗
PubMed1992

Synthesis and excitatory amino acid pharmacology of a series of heterocyclic-fused quinoxalinones and quinazolinones.

As part of our program aimed at the development of potent excitatory amino acid antagonists, we synthesized and evaluated a series of substituted 1,2,4-triazolo[4,3-a]quinoxalin-4(5H)-ones, 4, tetrazolo[1,5-a]quinoxalin-4(5H)-ones, 5, and pyrazolo[1,5-c]quinazolin-5(6H)-ones, 6, and an imidazo[1,2-a]quinoxalin-4(5H)-one, 7. In general, the same heterocycles which demonstrated the best affinity for the AMPA receptor also demonstrated the best affinity for the glycine site on the NMDA receptor complex. 1-Propyl-7,8-dichloro-1,2,4-triazolo[4,3-a]quinoxalin-4(5H)-one, 4d, was found to bind with the greatest affinity to the AMPA receptor with an IC50 of 0.83 microM and antagonized 40 microM AMPA-induced depolarization in the cortical slice preparation with an IC50 of 44 microM. 7,8-Dichloro-1,2,4-triazolo[4,3-a]quinoxalin-4(5H)-one, 4a, and 7,8-dichloroimidazo[1,2-a]quinoxalin-4(5H)-one, 7, possessed the best affinity for the glycine site with IC50 values of 0.63 and 1.26 microM, respectively. It is noteworthy that the SAR for the heterocyclic compounds did not directly parallel that of known quinoxalinediones (e.g. DNQX, 2, and DCQX, 15) at the AMPA receptor nor that of the kynurenic acids at the glycine site on the NMDA receptor complex.

Animals↗
PubMed1992

NMDA antagonist activity of (+/-)-(2SR,4RS)-4-(1H-tetrazol-5-ylmethyl)piperidine-2-carboxylic acid resides with the (-)-2R,4S-isomer.

The tetrazole-substituted amino acid (+/-)-(2SR,4RS)-4-(1H-tetrazol-5-ylmethyl)pip eri dine-2-carboxylic acid (LY233053, (+/-)-1) was resolved into its constituent enantiomers by treatment of a key intermediate in the synthesis of the racemic amino acid, ethyl (+/-)-cis-4-(cyanomethyl)-N-allylpiperidine-2-carboxylate, with either 2S,3S- or 2R,3R-di-p-toluoyltartaric acid. These resolved amines were then converted as for the racemate to the amino acids (-)-1 and (+)-1. The activity of this potent and selective NMDA antagonist was found to reside with the (-)-isomer of 1 (LY235723). X-ray crystallographic analysis of the 2S,3S-di-p-toluoyltartaric acid salt of ethyl cis-4-(cyanomethyl)-N-allylpiperidine-2-carboxylate showed that the resolved amine, and thus (-)-1, possessed the 2R,4S absolute stereochemistry. Affinity for the NMDA receptor was determined using the specific radioligand [3H]-(2SR,4RS)-4-(phosphonomethyl)piperidine-2-carboxylic acid ([3H]CGS 19755; IC50 = 67 +/- 6 nM), and selective NMDA antagonist activity was determined using a cortical slice preparation (IC50 versus 40 microM NMDA = 1.9 +/- 0.24 microM). This compound also demonstrated potent NMDA antagonist activity in vivo following systemic administration through its ability to block NMDA-induced convulsions in neonatal rats, NMDA-induced lethality in mice, and NMDA-induced striatal neuronal degeneration in rats.

Animals↗
PubMed1992

The neuroprotective actions of 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX) in a rat focal ischaemia model.

The neuroprotective effects of NBQX, a selective antagonist for the AMPA/kainate subtype of excitatory amino acid receptors, were investigated in a rat focal ischaemia model, involving permanent occlusion of the left middle cerebral artery (MCA). NBQX (3, 10 or 30 mg/kg) was administered i.v. immediately after MCA occlusion and again 1 h later. The highest dose of NBQX (2 x 30 mg/kg) gave significant protection against hemispheric (24%) and cortical (27%) ischaemic damage. The lower doses of NBQX (2 x 3 or 2 x 10 mg/kg) were ineffective. No protection was seen against caudate damage for any of the doses of NBQX tested. NBQX has a t1/2 of 30 min, therefore, a second experiment was done in which a dose of 30 mg/kg was given as an i.v. bolus followed immediately by an infusion of 10 mg/kg/h for 4 h, dosing was started immediately after MCA occlusion. This dosing regimen resulted in a mean plasma level over the 4 h of 17 micrograms/ml, and significant protection against the volume of hemispheric (29%) and cortical (35%) ischaemic damage, which was slightly better than that achieved with two bolus doses of 30 mg/kg. Once again no protection was seen against caudate damage. We conclude that NBQX, an AMPA/kainate antagonist was neuroprotective in a focal ischaemia model in the rat.

Analysis of Variance↗
PubMed1992

Specificity and potency of N-methyl-D-aspartate glycine site antagonists and of mephenesin on the rat spinal cord in vitro.

The potency, specificity and reversibility of various presumed glycine site N-methyl-D-aspartate (NMDA) antagonists was studied on neonatal rat spinal cord using the grease gap technique. 5,7-Dichlorokynurenate was the most potent and specific glycine site antagonist among the compounds tested. On the other hand mephenesin was a weak non-specific excitatory amino acid (EAA) antagonist; reduction of the response to NMDA was not reversed by D-serine. The EAA antagonist properties of mephenesin could explain its mode of action at the cellular level. The lack of effect of D-serine alone suggests that in our experimental conditions glycine sites on spinal neurones are occupied by an endogenous ligand.

Animals↗