WIN 63480, a hydrophilic TCP-site ligand, has reduced agonist-independent NMDA ion channel access compared to MK-801 and phencyclidine.

NMDA channel blockers are potentially advantageous therapeutic agents for the treatment of ischemia and head trauma, which greatly elevate extracellular glutamate, because they should most effectively inhibit high levels of receptor activation. A novel high affinity TCP site ligand, WIN 63480, does not produce MK-801- or PCP-like behavioral activation at anti-ischemic doses. While WIN 63480, MK-801 and PCP were all observed to be effective blockers of open NMDA channels, WIN 63480 had much less access to closed NMDA channels. This difference may be due to the fact that WIN 63480 is hydrophilic (logD = -4.1) while MK-801 and PCP are lipophilic (logD = +1.8). In vivo, closed channel access may result in a non-competitive profile of antagonism for MK-801 and PCP compared to a more uncompetitive profile for WIN 63480. Release of glutamate, and depolarization, are likely to produce a high level of NMDA receptor activation in ischemic areas compared to normal tissue. Consequently, at anti-ischemic doses, WIN 63480 may produce less inhibition of physiological NMDA-mediated processes in neural systems involved in behavioral regulation than MK-801 or PCP, leading to an improved side effect profile.

Synthesis and evaluation of 6,11-ethanohexahydrobenzo[b]quinolizidines: a new class of noncompetitive N-methyl-D-aspartate antagonists.

The synthesis and in vitro and in vivo evaluation of 12,13-cycloalkyl-6,11-ethanobenzo[b]-quinolizidines, a new class of noncompetitive N-methyl-D-aspartate (NMDA) antagonists acting at the PCP site on the NMDA receptor complex, is reported. Structure-activity relationship studies led to the identification of 10-hydroxy-(6 alpha,11 alpha,11 alpha beta,12R*,13S*)-1,3,4,6,11,11a,13,14,15,16-decahydro-12H- 6,11[1',2']-endo-cyclopenta-2H-pyrido[1,2-b]isoquinoline hydrobromide (5h) and 9-hydroxy-(6 alpha,11 alpha,11a beta,12R*,13S*)- 1,3,4,6,11,11a,13,14,15,16-decahydro-12H-6,11-[1',2']-endo-cycl ope nta-2H- pyrido[1,2-b]isoquinoline hydrobromide (5i), the most potent members of this series with Ki values of 2.3 +/- 0.2 and 2.3 +/- 0.5 nM, respectively. Molecular modeling studies revealed that this series of compounds occupies both lipophilic sites of the Andrews PCP receptor model and shares structural features which are common to other classes of known noncompetitive NMDA antagonists such as MK-801.

Discovery of 6,11-ethano-12,12-diaryl-6,11-dihydrobenzo[b]quinolizinium cations, a novel class of N-methyl-D-aspartate antagonists.

6,11-Ethano-12,12-diaryl-6,11-dihydrobenzo[b]quinolizinium cations 8, a novel class of N-methyl-D-aspartate (NMDA) antagonists acting at the phencyclidine site, have been identified. Structure-activity relationship studies around the lead compound 8a led to the identification of 12g (WIN 67870-2), one of the most potent compounds in this series. Compound 12g has a Ki = 1.8 +/- 0.2 nM vs [3H]TCP binding, has 700-fold selectivity for binding to the open state of the NMDA receptor-ionophore, and was devoid of MK-801- and PCP-like behavioral effects in rats. Compound 12g was neuroprotective in cultured mouse cortical neurons and exhibited antiischemic activity in a rat middle cerebral artery occlusion/reperfusion model of focal ischemia.

Novel NMDA antagonists: replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with heteroisoquinolinium cations.

Replacement of the pyridinium ring of 6,11-ethanobenzo[b]quinolizinium cations with thiazolium (4a and 4b) and N-methylimidazolium (4c and 4d) resulted in equipotent compounds in the [3H]TCP binding assay. The corresponding N-methyl-1,2,4-triazolium analogs were less potent in this assay. The thiazolium derivative 4b, with a Ki = 2.9 nM, is being evaluated as a possible neuroprotective N-methyl-D-aspartic acid (NMDA) antagonist.

Novel benzo[b]quinolizinium cations as uncompetitive N-methyl-D-aspartic acid (NMDA) antagonists: the relationship between log D and agonist independent (closed) NMDA channel block.

A series of permanently charged benzo[b]quinolizinium cations having lower lipophilicity than MK-801 or phencyclidine (PCP) were synthesized. Data relating agonist independent block of N-methyl-D-aspartic acid (NMDA) ion channels to log D are described. Closed channel access is predicted to result in a more noncompetitive profile of antagonism compared to selective open channel blockers, which are uncompetitive inhibitors. Reduced closed channel block may underlie the absence of PCP or MK-801-like behavioral side effects observed for benzo[b]-quinolizinium cations.

Identification, synthesis, and characterization of a unique class of N-methyl-D-aspartate antagonists. The 6,11-ethanobenzo[b]quinolizinium cation.

A series of novel N-methyl-D-aspartate antagonists acting at the phencyclidine site has been identified. Compound 2 has a Ki = 8 +/- 1 nM (vs [3H]thienylcyclidine, [3H]TCP) as a mixture of enantiomers. Resolution and further testing indicate that (-)-2, Ki = 4 +/- 0.7 nM, is a potent and selective TCP site ligand with neuroprotective activity in cultured neurons in the presence of excitotoxic concentrations of NMDA (IC50 = 26 nM). Compound (-)-2 is > 1000-fold selective for the TCP site vs a panel of receptor types including opiate, adrenergic, serotonergic, dopamine, adenosine, dihydropyridine, and benzodiazepine and displays increased selectivity for the activated (open) NMDA receptor-ion channel complex vs PCP and MK801 as measured by patch recordings in cultured, voltage-clamped neurons. Highly enhanced "open-channel" selectivity leads to tentative classification of these ligands as uncompetitive vs NMDA. Ligands with these characteristics may enable deconvolution of the pharmacologic effects associated with typical noncompetitive NMDA antagonists. We report here on the identification, synthesis, and activity of compounds of this structural class.

Evaluation of gastro-pulmonary aspiration by a radioactive technique: concise communication.

Seven selected patients were given 3-5 mCi of Tc-99m sulfur colloid orally at bedtime and the lungs were imaged in the morning. Two showed definite evidence of aspiration and one suggestive evidence. This is a simple, non-invasive method of demonstrating pulmonary aspiration of gastric contents.

Comparison of native matrix metalloproteinases and their recombinant catalytic domains using a novel radiometric assay.

A novel radiometric assay was developed for human fibroblast collagenase (matrix metalloproteinase-1, MMP-1), stromelysin (MMP-3), and their recombinant catalytic domains. Using this assay we were able to compare the native MMPs with the respective catalytic domains in terms of inhibitor affinities and peptide hydrolysis. The assay works on the same principle as an assay developed for carboxypeptidase (Rossier et al., Anal. Biochem. 1989, 178, 27-31) and is based on a synthetic peptide substrate, [1-benzoyl-14C]benzoyl-Pro-Leu-Ala-Leu-Trp- NH(CH2)4N(CH3)2(bnzPLALW-NX). The generation of product is measured by selective solvent extraction of radioactive product directly into scintillation cocktail; the entire assay, including the radioactivity measurement, is completed in a single 1-ml tube (96-well format) without removal or transfer of phases. Results of steady-state measurements demonstrated that peptide hydrolysis follows Michaelis-Menten kinetics with the fibroblast MMPs and their C-terminal deleted forms. The kinetic constants for hydrolysis of bnz-PLALW-NX, and for inhibition by actinonin, a natural peptide-hydroxamate, are essentially the same for the native and the C-terminally deleted MMPs.

Dimeric W3SO3 cluster complexes: synthesis, characterization, and potential applications as X-ray contrast agents.

Our continued research on the use of heavy metal cluster complexes as a new class of X-ray contrast agents in medical diagnostic imaging is described. A series of 2:3 cluster-ligand complexes, [(W(IV)3SO3)2L3]4- (L = linear polyaminopolycarboxylate ligands), were isolated from the reaction of aqua ion [W(IV)3SO3(H2O)9]4- (prepared in large quantities through an improved literature process) with respective ligands in refluxing DMF. The salts of [(W(IV)3SO3)2L3]4- complex anions were fully characterized using routine techniques such as elemental analysis, MS, HPLC, UV-vis, IR, and NMR. The solid structures of two complex anions, [(W(IV)3SO3)2(PDTA)3]4- and [(W(IV)3SO3)2(HO-PDTA)3]4-, were determined by X-ray crystallography. They are the first examples wherein two W(IV)3SO3 clusters are complexed and linked by three ligands that contain two terminal iminodiacetate (bis-IDA) groups. Complexation of the unstable aqua ion [W(IV)3SO3(H2O)9]4- with ligands has imparted desired biological compatibility to the tungsten metal cluster. These complexes are stable and highly soluble in H2O. The potential utility of such tungsten cluster complexes as X-ray contrast agents was evaluated in both in vitro and in vivo animal studies. In addition, the syntheses of several new linear polyaminopolycarboxylate ligands used in this study are reported.