oxadiazoles and Ischemic-Attack--Transient

Here, we report the synthesis and neuroprotective capacity of 27 compounds with a bisphenol hydroxyl-substituted 1,2,4-triazole core or 1,2,4-oxadiazole core for stroke therapy. In vitro studies of the neuroprotective effects of compounds 1-27 on sodium nitroprusside (SNP)-induced apoptosis in PC12 cells indicate that compound 24 is the most effective compound conferring potent protection against oxidative injury. Compound 24 inhibits reactive oxygen species (ROS） accumulation and restores the mitochondrial membrane potential (MMP). Moreover, further analysis of the mechanism showed that compound 24 activates the antioxidant defence system by promoting the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and increasing the expression of haem oxygenase 1 (HO-1). An in vivo study was performed in a rat model of transient focal cerebral ischaemia generated by the intraluminal occlusion of the middle cerebral artery (MCAO). Compound 24 significantly reduced brain infarction and improved neurological function. Overall, compound 24 potentially represents a promising compound for the treatment of stroke.

Topics: Animals; Antioxidants; Apoptosis; Behavior, Animal; Heme Oxygenase (Decyclizing); Humans; Infarction, Middle Cerebral Artery; Ischemic Attack, Transient; Ischemic Stroke; Male; Membrane Potential, Mitochondrial; Neuroprotective Agents; NF-E2-Related Factor 2; Nitroprusside; Oxadiazoles; PC12 Cells; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species

Antagonists of glutamate receptors of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype, as well as of voltage-gated sodium channels, exhibit anticonvulsive and neuroprotective properties in vivo. One can postulate that a compound that combines both principles might be useful for the treatment of disorders of the central nervous system, like focal or global ischemia. Here, we present data on the effects of dimethyl-(2-[2-(3-phenyl-[1,2, 4]oxadiazol-5-yl)-phenoxy]ethyl)-amine hydrochloride (BIIR 561 CL) on neuronal AMPA receptors and voltage-dependent sodium channels. BIIR 561 CL inhibited AMPA receptor-mediated membrane currents in cultured cortical neurons with an IC50 value of 8.5 microM. The inhibition was noncompetitive. In a cortical wedge preparation, BIIR 561 CL reduced AMPA-induced depolarizations with an IC50 value of 10.8 microM. In addition to the effects on the glutamatergic system, BIIR 561 CL inhibited binding of radiolabeled batrachotoxin to rat brain synaptosomal membranes with a Ki value of 1.2 microM. The compound reduced sodium currents in voltage-clamped cortical neurons with an IC50 value of 5.2 microM and inhibited the veratridine-induced release of glutamate from rat brain slices with an IC50 value of 2.3 microM. Thus, BIIR 561 CL inhibited AMPA receptors and voltage-gated sodium channels in a variety of preparations. BIIR 561 CL suppressed tonic seizures in a maximum electroshock model in mice with an ED50 value of 2.8 mg/kg after s.c. administration. In a model of focal ischemia in mice, i.p. administration of 6 or 60 mg/kg BIIR 561 CL reduced the area of the infarcted cortical surface. These data show that BIIR 561 CL is a combined antagonist of AMPA receptors and voltage-gated sodium channels with promising anticonvulsive and neuroprotective properties.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Anti-Anxiety Agents; Anticonvulsants; Batrachotoxins; Benzodiazepines; Cell Membrane; Cells, Cultured; Cerebral Cortex; Electroshock; Embryo, Mammalian; Glutamic Acid; In Vitro Techniques; Ischemic Attack, Transient; Male; Mexiletine; Mice; Neurons; Neuroprotective Agents; Oxadiazoles; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Receptors, AMPA; Sodium Channel Blockers; Sodium Channels; Synaptosomes; Veratridine

Changes in second messenger and neurotransmitter system receptor ligand binding induced by transient forebrain ischemia were studied in the gerbil hippocampus. The animals were allowed variable periods of recovery ranging from 2 h to 7 days after 5-min bilateral carotid artery occlusion. The binding of second messenger systems ([3H]inositol 1,4,5-trisphosphate ([3H]IP3)to inositol 1,4,5-triphosphate, [3H]forskolin to adenylate cyclase and [3H]phorbol 12,13-dibutylate to protein kinase C) and neurotransmitter receptor systems ([3H]PN200-110 to L-type calcium channels. [3H]N6-cyclohexyl-adenosine to adenosine A1 and [3H]quinuclidinyl benzilate to muscarinic cholinergic receptor) were assayed using quantitative autoradiography. In the CA1 subfield, 2 h after ischemia, [3H]IP3, [3H]forskolin, and [3H]quinuclidinyl benzilate binding activities significantly decreased by 25, 17 and 13%, respectively, though no morphological abnormalities were obvious. Six hours after ischemia, the [3H]phorbol 12,13-dibutylate binding activity in the stratum oriens of the CA1 subfield increased by 15%. One day after ischemia, [3H]PN200-110 binding activity in this subfield decreased by 26%, and 7 days after ischemia, [3H]phorbol 12,13-dibutylate and [3H]N6-cyclohexyl-adenosine receptor binding activities decreased in this subfield. In particular, at 7 days after ischemia, [3H]IP3 binding activity in the CA1 subfield showed a complete decline. In the CA3 subfield, [3H]PN200-110 binding activity decreased 2 days after ischemia, and [3H]IP3 and [3H]N6-cyclohexyl-adenosine binding activities decreased 7 days after ischemia. In the dentate gyrus, the structure of which remained histologically intact after ischemic insult, [3H]IP3 and [3H]forskolin binding activities decreased 7 days after ischemia. In contrast, the [3H]phorbol 12,13-dibutylate binding activity increased in the molecular layer of the dentate gyrus 7 days after ischemia. These results indicate that marked alteration of intracellular signal transduction precedes neuronal damage in the hippocampal CA1 subfield and that the histologically intact CA3 and dentate gyrus also shows modulated neuronal transmission after ischemia.

Topics: Adenosine; Adenylyl Cyclases; Animals; Autoradiography; Calcium Channel Blockers; Calcium Channels; Cerebral Cortex; Colforsin; Gerbillinae; Hippocampus; Inositol 1,4,5-Trisphosphate; Inositol 1,4,5-Trisphosphate Receptors; Ischemic Attack, Transient; Isradipine; Male; Neurons; Organ Specificity; Oxadiazoles; Phorbol 12,13-Dibutyrate; Protein Kinase C; Pyramidal Tracts; Quinuclidinyl Benzilate; Receptors, Cell Surface; Receptors, Cytoplasmic and Nuclear; Receptors, Muscarinic; Receptors, Purinergic; Second Messenger Systems; Time Factors; Tritium

The potent and selective AMPA receptor antagonist NBQX was tested for cytoprotective properties in an adult rat model of transient focal neocortical ischemia. Nineteen spontaneously hypertensive rats sustained 2 h of middle cerebral artery occlusion, followed by 22 h of recirculation. Ninety minutes following the onset of ischemia, at the time of, and 30 min following reperfusion, they received i.p. injections of either saline (n = 10) or 30 mg kg-1 of NBQX (n = 9). Saline-treated rats had a mean volume of neocortical infarction ( +/- s.d.) of 181 +/- 31 mm3, while NBQX-treated rats sustained significantly less damage, 125 +/- 19 mm3 (p less than 0.001). Regional cerebral blood flows during ischemia and reperfusion were not affected by the drug. We suggest that the AMPA receptor may play an important role in ischemic cerebral infarction.

Topics: Animals; Blood Pressure; Carbon Dioxide; Cerebral Infarction; Cerebrovascular Circulation; Ischemic Attack, Transient; Male; Oxadiazoles; Oxygen; Partial Pressure; Quinoxalines; Rats; Rats, Inbred SHR; Receptors, AMPA; Receptors, Neurotransmitter

The protective roles of Ca2+ channel blockers against ischemic hippocampal damage are still debated. We used autoradiography to study postischemic L-type Ca2+ channels (1,4-dihydropyridine Ca2+ channel blocker binding), adenosine A1 receptors, and muscarinic cholinergic receptors in the rat hippocampus using [3H]PN200-110 (PN), [3H]cyclohexyladenosine (CHA), and [3H]quinuclidinyl benzilate (QNB), respectively, in 49 rats subjected to 20 minutes of forebrain ischemia. The rats were decapitated after 1 (n = 7), 3 (n = 7), 6 (n = 8), 12 (n = 7), 24 (n = 6), 48 (n = 6), or 168 (n = 8) hours of recirculation; eight control rats were sham-operated but experienced no cerebral ischemia. Reduced receptor binding preceding the delayed death of CA1 pyramidal cells was first observed in the stratum oriens of the CA1 subfield. Significant reductions in [3H]PN, [3H]CHA, and [3H]QNB bindings of this stratum compared with control were noticed after 3 (35%, p less than 0.01), 12 (31%, p less than 0.01), and 1 (10%, p less than 0.05) hours of recirculation, respectively. By 168 hours after ischemia (when the populations of CA1 pyramidal cells were depleted) all strata in the CA1 subfield had lost most of their receptor sites, and [3H]PN, [3H]CHA, and [3H]QNB bindings in the stratum oriens were decreased to 23%, 30%, and 63% of control (p less than 0.01). Although [3H]PN binding in the CA3 subfield did not change significantly during 168 hours after ischemia, the histologically intact dentate gyrus exhibited a 31% loss of binding sites compared with control (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine; Animals; Autoradiography; Binding Sites; Calcium Channel Blockers; Hippocampus; Ischemic Attack, Transient; Isradipine; Male; Oxadiazoles; Quinuclidinyl Benzilate; Rats; Rats, Inbred Strains; Receptors, Muscarinic; Receptors, Purinergic; Time Factors; Tissue Distribution

Stimulation of inositol phospholipid hydrolysis by transmitter receptor agonists was measured in slices from hippocampus, cerebral cortex, and corpus striatum at various intervals after transient global ischemia in rats. Ischemia was induced through the four-vessel occlusion model. Stimulation of [3H]inositol monophosphate formation by excitatory amino acids was greatly enhanced in hippocampal slices prepared from ischemic rats at 24 h or 7 days after reperfusion. This potentiation was more evident using ibotenic acid and was also observed in cerebral cortex, but not in corpus striatum. This regional profile correlated with the pattern of ischemia-induced neuronal damage observed under our experimental conditions. The enhanced responsiveness to excitatory amino acids was always accompanied by an increase in both basal and norepinephrine-stimulated [3H]inositol monophosphate formation. In contrast, stimulation of [3H]inositol monophosphate formation by carbamylcholine was not modified in hippocampal or cortical slices from ischemic animals.

Topics: Animals; Brain; Carbachol; Cerebral Cortex; Corpus Striatum; Glutamates; Glutamic Acid; Hippocampus; Hydrolysis; Ibotenic Acid; In Vitro Techniques; Inositol Phosphates; Ischemic Attack, Transient; Kinetics; Male; Norepinephrine; Organ Specificity; Oxadiazoles; Quisqualic Acid; Rats; Rats, Inbred Strains; Reperfusion

Increasing evidence suggests a role for calcium ions in the pathophysiology of ischemic brain damage. The major mechanism allowing calcium entry from the extracellular compartment is the opening of voltage-operated calcium channels. In this line, we have explored the hypothesis that the characteristics of central L-type voltage-dependent calcium channels, labeled by the dihydropyridine ligand 3H-PN 200-110, may be modified by experimental ischemia. The results show that short-term mild ischemia, produced in the rat by 1 h of right carotid ligation, induces an increase in the number of 3H-PN 200-110 binding sites in the hippocampus ipsilateral to the side of carotid occlusion, accompanied by an increase in the dissociation constant value, whereas no changes in the kinetic parameters of the binding were observed in the other areas examined, i.e., the cortex and the striatum. The changes in hippocampus are transient: 96 h after the occlusion, binding parameters return to the control range. The modifications of the binding characteristics in the hippocampus may be related to alterations of Ca2+ fluxes through L-type calcium channels.

Topics: Animals; Calcium; Calcium Channel Blockers; Cell Membrane; Cerebral Cortex; Corpus Striatum; Hippocampus; Ion Channels; Ischemic Attack, Transient; Isradipine; Kinetics; Male; Oxadiazoles; Rats; Rats, Inbred Strains